Queen ants in southern Europe produce male clones of an entirely different species — tearing up the playbook of reproductive biology and suggesting we need to rethink our understanding of species barriers.

The workers in Iberian harvester ant (Messor ibericus) colonies are all hybrids, with queens needing to mate with males from a distantly related species, Messor structor, to keep the colony functioning. But researchers found that some Iberian harvester ant populations have no M. structor colonies nearby.

"That was very, very abnormal. I mean, it was kind of a paradox," study co-author Jonathan Romiguier, an evolutionary biologist at the University of Montpellier, told Live Science. The team initially believed there was a sampling issue, but they went on to find 69 regions where this was the case.

"We had to face the facts and try to see if there is something special within Messor ibericus colonies," Romiguier said.

In setting out to resolve this paradox, Romiguier and his team found that queen Iberian harvester ants also lay eggs containing male M. structor ants, with these males ultimately fathering the workers. This discovery, published Sept. 3 in the journal Nature, is the first time any animal has been recorded producing offspring from another species as part of their normal life cycle.

"In the early stages, it was kind of a joke in the team," Romiguier said. "But the more we got results, the more it became a hypothesis and not a joke anymore."

Related: Single bee is making an immortal clone army thanks to a genetic fluke

Ants are eusocial insects, meaning their colonies form cooperative super-organisms predominantly made up of infertile females, called workers, and a small number of reproductive females, called queens. Males solely exist to fertilize queens during their mating flight and die soon after.

Queens only mate once in their lives and store the sperm from this meeting in a special organ. She then draws from this sperm stash to lay new eggs containing one of three types of offspring: queens, workers or males.

However, Iberian harvester ants mating with males of their own species can only produce new queens. This is thought to be a result of selfish queen genes, where the DNA from male M. ibericus guarantees its survival across generations by biasing larvae to produce fertile queens rather than infertile workers — known as "royal cheaters."

To avoid this, queens must use sperm from male M. structor ants to produce their workers.

This was why the presence of thriving isolated M. ibericus colonies was such a conundrum.

To find answers, the researchers first sampled 132 males from 26 Iberian harvester ant colonies to figure out whether there were M. structor males present. They found that 58 were covered in hair and 74 were hairless. A closer inspection of the nuclear genomes of a subset of these ants revealed that all hairy ones were M. ibericus and all bald ones were M. structor.

But this was not proof that the queens were laying male eggs of two different species — there could have been some hidden M. structor queens producing the odd male. So the team sequenced the mitochondrial DNA, which is passed down by the mother, of 24 of the M. structor males, and found it came from the same mother as the M. ibericus male nestmates.

"This was the detail that made me realize that 'maybe we are on to something very, very, very big,'" Romiguier said.

The team then separated 16 queens from laboratory colonies and looked at the genetic sequences of their freshly laid eggs. They found that 9% of their eggs contained M. structor ants. They then directly observed a single queen producing males of both species by monitoring its broods weekly over an 18-month period.

Together, all these findings show that Iberian harvester ant queens are cloning M. structor males and not passing on any of their own nuclear DNA. Researchers now need to pinpoint the exact mechanism underlying this cloning, Romiguier said, and find out at what point the maternal DNA is removed.

Denis Fournier, an evolutionary biologist and ecologist at the Free University of Brussels, Belgium, who was not involved in the research, said that it was "almost like science fiction" when he first learned of this discovery. "It's jaw-dropping! Most of us learn that species boundaries are firm, yet here is a system where ants regularly cross them as part of normal life," he told Live Science in an email.

The team have called this new reproductive system "xenoparity," meaning the birth of a different species. Romiguier said the team aren't exactly sure when this system first emerged in the Iberian harvester ants, but it's somewhere between when M. ibericus and M. structor split along different evolutionary paths 5 million years ago and a few thousand years ago.

"This discovery is a great reminder to stay open to the unexpected," Fournier said, noting that the finding opens up new questions about cooperation, conflict and dependency in nature. "Now that we know such a system is possible, it’s exciting to think that old, puzzling data might suddenly make sense in light of this discovery," he added.

Doctors discovered that a girl's sudden and mysterious belly pain had a rare cause: One of her fallopian tubes was completely twisted. 

This condition is rare, overall, but especially rare in children.

The 11-year-old girl's severe abdominal pain had come on over the course of a day and triggered nausea and vomiting, according to a recent report of the case, published Aug. 9 in the journal Case Reports in Surgery. At the emergency room, doctors found that the pain extended from the center of the girl's lower stomach below the belly button to the right side of her pelvis. Tests showed elevated levels of immune cells in her blood, and an ultrasound revealed that the muscles that normally move food through the digestive system were not contracting properly.  

Upon further examination, doctors discovered that the girl had a blob of excess fluid in her pelvis measuring about 2.3 by 2.8 by 1.9 inches (5.9 by 7.2 by 4.9 centimeters). However, her ovaries, located near the fluid buildup, seemed to be functioning normally and didn't have any obvious signs of damage. 

Related: Doctors perform 1st-of-its-kind brain surgery on a fetus in the womb 

The doctors performed an additional scan to look closer at the fluid and found that it was in contact with the girl's ovaries but wasn't coming directly from them. She also had extra fluid that was just floating "free" in her pelvis. Initially, they thought she might have an inflammatory disease in the pelvis that had caused a swollen mass to form in tissues of the reproductive system, or that it might be caused by a condition in another part of the body, like the intestines. 

Unsure of this fluid's mysterious cause, the team decided to conduct a type of surgery known as laparascopy, in which doctors make small incisions in the abdomen and guide a tiny camera inside. The procedure confirmed that the free fluid in her pelvis looked a lot like blood, and it revealed the source of that blood: the girl's left fallopian tube was completely twisted. This twist, or "torsion," caused a bleeding cyst to develop, which, in turn, stopped the flow of blood to the tube and led to tissue death. 

This rare condition, in which a fallopian tube gets twisted without affecting its nearby ovary, is known as isolated fallopian tube torsion (IFTT). It's slightly more common for ovaries to twist, or for an ovary and fallopian tube to twist together; but ovarian torsion is still relatively uncommon, affecting about 6 in 100,000 women in a year, a South Korean study found.  

By comparison, IFTT is estimated to affect around 1 in 1.5 million reproductive-age women worldwide, and it's even rarer in pediatric and postmenopausal populations. Most of the time, IFTT causes the right fallopian tube to twist, but 40% of cases occur in the left tube. 

The condition is difficult to diagnose, as there isn't one definite set of symptoms. Patients may have severe, sharp pain in their lower belly, which is often accompanied by nausea and vomiting. However, these common symptoms make IFTT easy to confuse with other conditions, such as appendicitis or urinary tract disease. 

The team had to remove the girl's left fallopian tube due to the dead tissue, but they were able to spare her right tube and both ovaries, and she completely recovered. The authors of the case report noted that the procedure could affect the patient's fertility in the future, but because she has both ovaries and an intact tube, "it is expected that it will not have major repercussions."  

They added that IFTT should be treated as quickly as possible, because delays of 10 hours or more can greatly increase the risk of tissue death. 

The exact cause of IFTT is unclear, but scientists have several theories as to why it happens, the authors added. Some theorize, for example, that it may be caused by abnormalities in the sheet of tissue that normally surrounds the fallopian tubes, or perhaps by problems in the fallopian tube itself that disrupt how it shuttles eggs to the uterus. Others say it may be driven by untreated infections that lead to fluid buildup; physical trauma; or "sudden changes in body position" that cause the reproductive organs to shift in an odd way. 

The 11-year-old didn't have any known risk factors for torsion upon arriving at the emergency room. "However, she did have a large tubal cyst, which likely facilitated torsion," meaning it likely exacerbated the twist as it formed, the authors noted.

A bacteria commonly found in the mouth and gut could be what triggers endometriosis, a small new study suggests. 

And the early research hints that antibiotics could combat the painful and chronic disease that causes tissues lining the uterus to grow outside of it. 

Scientists in Japan discovered the link while studying vaginal swab samples taken from 155 women, of which 79 had endometriosis and 76 did not, according to a study published Wednesday (June 14) in the journal Science Translational Medicine.

Nearly two-thirds of the women with endometriosis also tested positive for Fusobacterium, a genus of bacteria that can contribute to gum disease and other illnesses of the mouth and gut, in their uterine lining. Only 1 in 10 of the healthy women did, according to a statement.

"Previously, nobody thought that endometriosis came from a bacterial infection, so this is a very new idea," co-author Yutaka Kondo, a cancer biologist from Nagoya University Graduate School of Medicine in Japan, told The Washington Post.

Related: Why is endometriosis so hard to diagnose?

To demonstrate that Fusobacterium was the culprit, the researchers infected mice with the bacteria, then examined the uterine lining. The mice developed lesions associated with endometriosis. Once scientists gave the mice antibiotics, they "saw improved lesion formation" with the lesions decreasing in both size and number, according to the statement.

"Eradication of this bacterium by antibiotic treatment could be an approach to treat endometriosis for women who are positive for Fusobacteria infection, and such women could be easily identified by vaginal swab or uterus swab," Kondo said in the statement. 

However, Kondo emphasized that more research needs to be conducted before "treatments can be derived from this new study," according to The Washington Post. 

Endometriosis is a painful and debilitating disease that, in severe cases, can cause infertility. It affects approximately 10% of women and girls of reproductive age around the world, according to the World Health Organization. That equates to about 11% of American women between the ages of 15 and 44, according to the Office of the Assistant Secretary for Health.

"Medicine puts a Band-Aid on it," Dr. Allison K. Rodgers, a reproductive endocrinologist at the Fertility Centers of Illinois who was not involved with the study, told The Washington Post. "I can give you medicine to stop your periods; I can give you birth control pills; I can give you pain meds; I can cut it out with surgery. But we haven't figured out the why, and once we start figuring out the why, we'll be able to design targeted approaches for treatment."

Right now the only treatments for endometriosis are hormonal medications, such as birth control pills, or surgery to remove the reproductive organs, according to the Mayo Clinic. 

The Department of Obstetrics and Gynecology at Nagoya University Hospital is currently conducting clinical trials of the antibiotic treatment on patients, according to the statement.

Scientists have developed the world's first "vagina-on-a-chip," a small device that contains live human cells and replicates the cellular environment found inside the vaginal canal. 

By adding bacteria to the device, aptly named the Vagina Chip, researchers can study how different microbes affect the health of the vagina, the team reported in a new study, published Nov. 26 in the journal Microbiome. They can also test how different drugs and probiotics change the composition of the vaginal microbiome, the community of microorganisms living within the canal. 

"The vaginal microbiome plays an important role in regulating vaginal health and disease, and has a major impact on prenatal health," first author Gautam Mahajan, a former researcher at Harvard University's Wyss Institute for Biologically Inspired Engineering, said in a statement. "Our human Vagina Chip offers an attractive solution to study host-microbiome interactions and accelerate the development of potential probiotic treatments," which work by introducing beneficial bacteria into the vagina, said Mahajan, who now works at the organ-on-a-chip company Emulate, Inc. in Boston.

The Vagina Chip device measures only 1 inch (2.54 centimeters) long and contains donated cells from two women; the cells were collected from the lining of the vagina and from the connective tissue that runs beneath the lining, according to The New York Times. These two types of cells sit on either side of a permeable membrane, which replicates the 3D structure of the vaginal wall. 

Related: Vaginal bacteria can vary widely in healthy women 

The scientists allowed these cells to multiply for five days in the device before adding the sex hormone estradiol, a form of estrogen. The hormone changed which genes were switched "on" in the tissues and triggered the production of mucus, as would occur in vivo.

With their device complete, the team ran several tests with bacteria commonly found in the vagina, namely, several strains of Lactobacillus bacteria; studies suggest that these microbes make up more than 70% of a healthy vagina's microbiome, according to the Wyss Institute statement. 

The researchers found that the Lactobacillus bacteria successfully produced lactic acid in the Vagina Chip, thus driving down the pH of the tissue inside. A healthy vagina typically has a pH of 4.5 or less, meaning it's acidic, and this acidity helps prevent the growth of harmful bacteria that could cause disease. In addition, adding the Lactobacillus bacteria reduced the number of inflammatory molecules circulating in the tissues.

Having run experiments with "good" bacteria, the team did the same with "bad" bacteria, meaning bugs associated with bacterial vaginosis (BV), a common vaginal infection caused by the overgrowth of specific bacteria. These bugs include Gardnerella vaginalis, Prevotella bivia, and Atopobium vaginae, and when introduced into the Vagina Chip, all three bacteria caused the pH of the device to rise along with the number of inflammatory molecules and damaged vaginal cells.

BV increases the risk of sexually transmitted diseases, such as chlamydia and gonorrhea, both of which can negatively affect future fertility by triggering a harmful inflammation, according to the Centers for Disease Control and Prevention (CDC). If developed during pregnancy, BV also raises the risk that a baby will be born prematurely or at a low birth weight. The new vagina-on-a-chip could help scientists develop new and better treatments for BV, sexual health physician Achyuta Nori of St. George's, University of London, who was not involved with the study, told Scientific American. 

"This is an opportunity to bring women's health into the modern times, using modern technology," Nori said. The chip offers an advantage over testing therapies in lab animals like mice, whose vaginal microbiomes greatly differ from humans'; in addition, it's historically been difficult for drug developers to recruit human patients for BV treatment trials, partly due to patients' concerns over safety, experts told the Times. 

That said, organ-on-a-chip technology does have its limitations, so it cannot perfectly capture all the factors that influence the human vaginal microbiome. But the Vagina Chip is a good first step towards further research.

The human body is a complex network of systems that work together to keep life-sustaining processes running smoothly. These systems break down food for fuel, clear away waste, repair damaged tissues and DNA, fight infectious germs and monitor the outside world so we can move through it safely. 

Many scientists spend their days working to understand how each bodily system performs its jobs, how the systems interact, and what can happen when one or more of them falter. Such malfunctions can stem from aging or disease, for instance, and through medical care, doctors aim to get derailed systems back on track. 

Here's a quick rundown of the systems of the human body, its vital organs and its "vestigial" organs, as well as a few fascinating facts about how the body works.

What are the different systems of the human body? 

Our bodies consist of a number of biological systems that carry out specific functions necessary for everyday living. Some organs and tissues play roles in multiple systems at once.

Related: Strange, two-faced brain cells confirmed to exist, and they may play a role in schizophrenia 

Circulatory: The job of the circulatory system is to move blood, nutrients, oxygen, carbon dioxide and hormones around the body. It consists of the heart, blood, blood vessels, arteries and veins. According to the Cleveland Clinic, the adult human body's network of blood vessels is more than 60,000 miles (around 100,000 kilometers) long. 

Digestive: The digestive system consists of a series of connected organs that together allow the body to break down and absorb nutrients from food and remove waste. It includes the mouth, esophagus, stomach, small intestine, large intestine, rectum and anus. The large intestine is home to microorganisms that are collectively called the gut microbiome and influence our health in various ways. The liver and pancreas also have roles in the digestive system because they produce digestive juices filled with enzymes to break down the components of food, such as carbohydrates, fats and proteins, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

Endocrine: The endocrine system consists of a network of glands that secrete hormones — long-range chemical messengers that regulate how cells and tissue function — into the blood. These hormones, in turn, travel to different tissues and regulate many bodily functions, such as metabolism, growth and sexual function, according to Johns Hopkins Medicine. For example, the pancreas releases the hormones insulin and glucagon to regulate blood sugar. Conditions like diabetes and insulin resistance arise from the body having too little insulin or not responding to it adequately. 

Related: Meet the 'exclusome': A mini-organ just discovered in cells that defends the genome from attack

Immune: The immune system is the body's defense against bacteria, viruses and other pathogens that may be harmful. Components of the system include the lymph nodes, which contain infection-fighting cells called lymphocytes. These lymphocytes are one of many types of leukocyte, or white blood cell. The immune system also includes the spleen, the bone marrow and a gland called the thymus. The immune system can learn to recognize antigens — proteins on the surface of bacteria, fungi and viruses — and alert the body to their presence. Some immune cells make proteins called antibodies that attach to these antigens and mark invaders for destruction. 

Lymphatic: The lymphatic system includes the lymph nodes, lymph ducts and lymph vessels and is considered part of the immune system. Its main job is to make and move lymph, a clear fluid that contains white blood cells. The lymphatic system also removes excess lymph fluid from the body's tissues and returns it to the blood.

Nervous: The nervous system controls both voluntary actions, such as conscious movements, and involuntary actions,like breathing, and it sends signals to and detects signals from different parts of the body. Conscious actions are controlled by the somatic nervous system, while involuntary actions are controlled by the autonomic nervous system. The autonomic nervous system dictates whether we're in "rest and digest" or "fight or flight" mode. The nervous system can further be split up into the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system, or the nerves connecting the CNS to every other part of the body.

Muscular: The body's muscular system consists of hundreds of muscles that aid movement, blood flow and other bodily functions, according to the Library of Congress. There are three types of muscle: skeletal, which is connected to bone and helps with voluntary movement; smooth, which is found inside organs and helps to move substances through them; and cardiac, which is found in the heart. The body's largest muscle by mass is the gluteus maximus, but the two latissimus dorsi are the largest in terms of surface area.

Related: Why is it harder for some people to build muscle than others?

Reproductive: The reproductive system allows humans to produce offspring. The male reproductive system includes the penis and the testes, which produce sperm. The female reproductive system includes the vagina, uterus and ovaries, which produce eggs. During fertilization, a sperm cell will fuse with an egg cell that, in a successful pregnancy, will then implant in the uterus. The fertilized egg will then mature into what's called a blastocyst, then an embryo and, finally, a fetus. A placenta forms to support this process. 

Skeletal: Our bodies are supported by the skeletal system, which contains between 206 and 213 bones in an adult human body, due to slight variations in people's anatomy, according to the medical resource StatPearls. These bones are connected by tissues called tendons, ligaments and cartilage. As infants, humans have about 300 bones, but some fuse together as the child grows. The skeleton not only helps us move but is  also involved in the production of blood cells and the storage of calcium. The teeth are also part of the skeletal system, but they aren't considered bones. The smallest bones in the body are found in the ear, and the largest is the femur, or thigh bone, which is also one of the heaviest body parts.

Respiratory: The respiratory system allows us to take in oxygen and expel carbon dioxide through breathing. It includes the lungs; trachea, or windpipe; and the diaphragm, a muscle that pulls air into and pushes air out of the lungs.

Urinary: The urinary system helps eliminate a waste product called urea, which is produced when certain foods are broken down. The system includes the two kidneys; two ureters, or tubes leaving the kidneys; the bladder; two sphincter muscles; and the urethra. The kidneys filter blood in the body to make urine that then travels down the ureters to the bladder and exits the body through the urethra.

Integumentary: The skin, hair and nails make up the integumentary system. Skin is the body's largest organ. It protects our innards from the outside world, serving as our first defense against bacteria, viruses and other pathogens, for instance. Our skin also helps regulate body temperature and eliminate waste through perspiration, or sweat. 

Related: Scientists discover new way humans feel touch 

What are the body's vital organs?

Click the purple circles to learn about the body's vital organs, including the brain, lungs, heart, liver and kidneys. They're considered vital because you need a functioning brain, heart, liver, at least one kidney and at least one lung to survive. That said, there are medical devices and treatments that can make up for a loss of function in these organs, at least temporarily — for example, ECMO machines can do the work of the heart and lungs, and dialysis can filter the blood of people with kidney failure.

Fast facts

• The average adult male body contains about 36 trillion cells, the average adult female body contains 28 trillion cells and a 10-year-old has about 17 trillion. 
• It's often said that there are 78 organs in the human body, but the number actually differs depending on whom you ask. 
• There's a popular idea that the body replaces itself every seven years. But that's not really true, because tissues renew themselves at different rates. 
• Oxygen is the most common element in the human body, followed by carbon. 
• The average adult body contains about 1.2 to 1.5 gallons (4.5 to 5.5 liters) of blood. 
• Humans' average body temperature has fallen slightly over time, so it's no longer 98.6 degrees Fahrenheit (37 degrees Celsius). 
• The most detailed map of the human brain to date contains more than 3,300 types of brain cells. 

What are vestigial organs?

There are arguably some parts of the human body that don't serve any useful purpose, such as the male nipple. That said, the usefulness of some organs is still up for debate, as scientists have often judged the worth of body parts before discovering their purposes. 

Broadly speaking, vestigial body parts are defined as those that have lost their original physiological significance to humans over the course of evolutionary history. The idea is that, while we inherited them from an ancient ancestor, we could really do without them in the modern day. 

Wisdom teeth are held up as one example of a vestigial body part, as the modern human jaw is often too small to accommodate a third set of molars. Some people also carry remnants of a vomeronasal organ that is largely thought to be nonfunctional in humans; animals use equivalent organs to detect each other's pheromones. 

Some scientists consider the human tailbone, or coccyx, vestigial because it's no longer a full-blown tail. But it's far from useless, as it still anchors many muscles, ligaments and tendons. And the appendix has gotten a bad rap for supposedly being both vestigial and useless, but more recently, scientists have uncovered possible functions for the long-maligned body part. 

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

Editor's note: This page was last updated on April 5, 2024.

Whether you're a frog or a human, reproduction is an occasion of cellular celebration. New research finds that in species separated by millions of years of evolution, a fertilized egg gives off a fireworks show of metal atoms. 

This microscopic shower of sparks was discovered in human eggs in 2014, leading researchers  to wonder what purpose the sudden release of metals served. Now, the same researchers who discovered the original fertilization fireworks have found that the same thing happens in fertilization in frogs — organisms that are separated from humans by 300 million years of evolution. Both manganese and zinc atoms explode from the eggs' membranes right after the sperm make contact. 

"It's underscoring that zinc fluctuations are an ancient and conserved part of the regulatory mechanisms controlling development," said study leader Thomas O'Halloran, a chemist at Northwestern University in Illinois. He and his colleagues are still working out the details, but they believe that the manganese and zinc may both prime the egg for future development and protect it against being fertilized by more than one sperm. 

Related content: Sexy swimmers: 7 facts about sperm 

Fertilization fireworks

O'Halloran and his team learned in 2014 that when a human egg enters the final stages of development in preparation for fertilization, it starts "bulking up" on zinc, pulling in 50% more of the metal from its surroundings than earlier in its development. They've since learned that if an egg fails to incorporate all this zinc, it cannot be fertilized. Exactly what the zinc is doing at this pre-fertilization stage isn't clear, but the researchers have some early data to hint that the zinc primes other proteins in the egg get the egg ready to become pluripotent — meaning the egg is capable of dividing into every cell type in a new organism's body. 

In this stage, O'Halloran told Live Science, the zinc seems to be playing a communication role, allowing parts of the cell to signal to one another. But at the moment of fertilization, zinc seems to do something else: First, it gathers in tiny compartments called vesicles in the cell membrane, and then it releases in what the researchers call a "zinc spark," with billions of metal atoms exploding outward at once. 

Since finding this zinc spark in human eggs, the researchers have discovered it in monkeys, cows and mice. Turning toward more ancient lineages than mammals, they have now found a similar spark in the African clawed frog (Xenopus laevis). They reported their findings June 21 in the journal Nature Chemistry.

Frog eggs are nice to study, O'Halloran said, as they're much larger than mammalian eggs. This means they consist of more atoms, which makes it easier to use microscopy to see the metal atoms. 

"The frog has been really giving us some special information that we couldn't get from the other systems," O'Halloran said.

Nutrients for fertility

One surprise was that when a frog egg is fertilized, it doesn't just release zinc; it also releases manganese. O'Halloran and his team aren't sure whether this manganese release is specific to frogs or if it might happen in mammals as well. Their threshold for detecting the metal in mammalian egg studies wasn't high enough to tell for sure, given that mammal eggs are so much smaller than amphibian eggs. It might be that the manganese is a particular quirk of amphibian eggs, which are fertilized and develop outside the mother's body. Or it could be that a manganese spark occurs in humans too and more detailed research is needed to observe it. 

Either way, the eruption of manganese and zinc from the egg at fertilization might be a way to prevent what O'Halloran called the "catastrophe of polyspermy." Polyspermy means the fertilization of an egg by multiple sperm. This leads to the problem of too many genomes and kills the developing zygote. 

In the new study, the researchers showed that levels of zinc and manganese prevent sperm from fertilizing an egg, leading them to suspect that the fireworks show is in fact a protective mechanism that may block additional sperm from breaching the egg. 

Zinc and manganese are interesting nutrients, O'Halloran said, because the body cannot synthesize these metals nor break them down. It has to get them from the diet, store just the right amount and excrete any extra that it's not using. 

"They're more complex nutrients than most any vitamin or protein or fat," he said. 

Zinc is found throughout the body and was once thought to simply help enzymes in cells complete chemical reactions. More recently, O'Halloran said, it's become clear that zinc is sometimes used as a cellular messenger. Manganese, on the other hand, hasn't yet been shown to have much of a messenger role, but research is limited, O'Halloran said. 

The main thrust of the research is simply unraveling the complex ways in which egg cells function. After all, O'Halloran said, these cells start to develop when the female is still a fetus, and have to remain in a state of stasis for years before suddenly developing very rapidly in preparation for fertilization. Ultimately, the role of zinc and other metals in this process could point to questions for fertility researchers, such as whether a lack of zinc ever plays a role in infertility. 

"I think it points to the fact that you have to have a really complex array of elements available for cells during reproduction," O'Halloran said. 

Originally published on Live Science.

Fact: Whale sharks — the largest known fish in the sea and some of the largest creatures on Earth — exist. That means they must be reproducing.

Despite this, scientists have never actually seen two whale sharks mating. This is partly because the animals are endangered; whale sharks are so large — averaging about 32 feet (10 meters) long and weighing tens of thousands of pounds — that they are highly susceptible to human threats like drilling, fishing and shipping. Scientists also suspect that the fish migrate enormous distances through the world's tropical seas to reach special whale shark mating grounds, which researchers simply haven't located yet. [Gallery: The Mysterious Lives of Whale Sharks]

Now, thanks to a fortuitous flyby in Western Australia, biologists are one step closer to learning how whale sharks make the proverbial beast with two humpbacks. While flying over Australia's Ningaloo Reef in mid-June, commercial tour pilot Tiffany Klein spotted an adult male whale shark trying to catch a juvenile female's attention by zigzagging through the sea for more than an hour — and then, unsuccessfully, trying to mate with her.

Klein pointed out the frisky whale to nearby researchers from the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia's federal science agency. CSIRO researchers observed the encounter from sea while Klein photographed from above, effectively providing the world's first record of whale shark mating behavior.

"Whether he was successful or not, this is the first time we've seen an attempted copulation by a male whale shark with a female," George Burgess, director emeritus of the Florida Program for Shark Research, told Live Science. (Burgess did not witness the recent sighting.) "We still don't know what the mating behavior of a mature female would be, but it's one step forward in our understanding of whale shark reproductive biology."

Learning from shark sex

Burgess said scientists can take a few key lessons from the attempted mating, beginning with the male shark's capricious behavior beforehand.

In an interview with the Australian Broadcasting Corporation, Klein and the CSIRO researchers described the male's behavior as "erratic," swimming in zigzags and making sudden dives much deeper than an adult male normally would. Burgess said this can be interpreted as the sort of peacocking behavior seen in many male mammals and birds, which is designed to get a female's attention and show off the potential suitor's viability.

Because the encounter took place very close to the surface, where whale sharks tend to hang out eating the plankton that makes up much of their diet, it's possible that the young female was feeding and didn't even notice the male's "hot-to-trot" display, Burgess said.

When the male shark finally did approach the female, he swam up from below. This is not unusual for sharks, Burgess said, as males copulate with one of their two claspers — essentially, a pair of very flexible penises — that allow the males to approach mates from multiple angles. The tips of this male’s claspers were spread, or "flared," the researchers noted, meaning he clearly had mating on the mind.

Because the male shark here was fully grown (measuring about 30 feet, or 9 meters), however, and the female was still a juvenile, she rejected his advances and swam off. What drove the male to try and reproduce with a young shark who wasn't ready? It may have been simple desperation, Burgess said, as Ningaloo Reef is populated mainly by immature male sharks, suggesting it is not a common reproductive site.

"This big male came in, couldn't find an adult female to mate with, and made an attempt on a juvenile female anyway," Burgess suggested.

Though the mating attempt was doomed to fail, it still provides researchers with an invaluable opportunity to learn about one of the most elusive mating rituals in the sea. Because whale sharks are a protected species, researchers aren't allowed to capture them for study.

Still, not all seafarers play by the rules. In 1995, for example, a pregnant female whale shark was harpooned by a commercial fishing vessel in Taiwan. When she was later dissected, 300 pups were found developing inside her. Scientists may still not know how, exactly, these giants of the deep go about mating — but, whatever they're doing, it seems to work.

Originally published on Live Science.

• In Photos: Spooky Deep-Sea Creatures
• Whale Album: Giants of the Deep
• Image Gallery: Mysterious Lives of Whale Sharks

When it comes to making babies, it usually takes two to tango. But Anna, a 10-foot-long (3 meters) anaconda at Boston's New England Aquarium, did it solo. Earlier this year, Anna gave birth to 18 snake babies all by herself, no male snakes required.

Aquarium staff had no idea Anna was pregnant until they saw her during delivery (anacondas don't lay eggs, instead having live births). Immediately, aquarium biologists suspected that Anna had given birth via parthenogenesis, which in Greek means "virgin birth." In other words, Anna's babies contain genetic information only from Anna.

Parthenogenesis doesn't always result in perfect copies. Genes come in pairs — one set from each parent (or in Anna's case, one set from each egg). In some cases of parthenogenesis, these sets of genes get shuffled, so even though the genes are the same in the babies, they're not arranged in the same order, meaning not all offspring are clones. However, in Anna's case, these babies were complete clones. [In Images: Hungry Python Eats Porcupine Whole] 

"She's essentially giving birth to herself, oddly enough," David Penning, an assistant professor of biology at Missouri Southern State University, who wasn't involved with Anna's case, told Live Science. 

Before aquarium staff could be absolutely sure that Anna had experienced parthenogenesis, they had to double-check that the other snakes in Anna's enclosure were, in fact, female. The animals were. Then, the staff ran DNA tests for the new snake babies. The new snakes were 100% Anna.

In sexual reproduction, a sperm and egg combine, mixing together their genetic information into a brand-new cell, called a zygote. In Anna's case, no sperm was necessary. Instead, all it took was one egg, Penning said. Because an egg contains only half the genetic information needed to form a zygote, it would have had to first clone itself before effectively self-fertilizing. Imagine making a photocopy, then stapling the two identical copies together, Penning said. That's parthenogenesis.

The phenomenon has rarely been documented in snakes or other reptiles. (Just one other instance of anaconda parthenogenesis has been documented, in a U.K. zoo in 2014.) But it may be more common in the wild than scientists assume, Penning said. Most documented cases occur in captivity, when a creature like Anna, isolated from males her whole life, suddenly and unexpectedly produces babies. But in the wild, it's challenging to determine whether a snake is reproducing via sexual reproduction or parthenogenesis, Penning said.

"I don't think we really have a handle on the prevalence of this," he said.

Of Anna's 18 new anacondas, only two survived. Fifteen of the babies were stillborn, and one died a few days later. High mortality rates are common for babies born via parthenogenesis, Penning said. Moreover, this reproductive strategy creates many of the problems seen in inbred populations, including high numbers of harmful genetic mutations.

In wild populations, parthenogenesis can also cause problems when an environmental stressor, such as a new disease or a natural disaster, comes along, Penning said. That's because it's easy to wipe out a whole population when they all have the same genetic traits.

Despite the drawbacks of parthenogenesis, it's a win-win situation when species have the option to switch back and forth between sexual and asexual reproduction. When population levels get low in the wild, "having more copies of yourself isn't that bad of an idea," Penning said.

Anna's babies, now 5 months old and 2 feet (0.6 m) long, aren't ready to be introduced to the public just yet. Aquarium staff are caring for them behind the scenes, handling the snakes daily to get them used to human contact.

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Originally published on Live Science.

The term "stem cells" has become part of the mainstream lexicon, likely to be overheard in conversations anywhere from a baseball game to cocktail get-togethers. But what exactly are these cells?

Along with phrases such as "that's just immoral" or "stem cells could be the end-all cure," one could easily weave in some technical tidbits about these microscopic, yet significant, cells.

Stem cells are considered the "engine" cells of regeneration in that they are self-renewing and able to duplicate, or clone, themselves. These special cells are used in the rapidly growing field of regenerative medicine to halt or even reverse chronic diseases. Regenerative medicine seeks to repair or replace tissues or organs that have been damaged by trauma, disease or congenital defects, according to the McGowan Institute for Regenerative Medicine at the University of Pittsburgh.

There are three types of stem cells: embryonic, umbilical cord (also known as mesenchymal, or MSC), and adult stem cells. Embryonic stem cells are considered pluripotent, meaning they can give rise to all of the cell types that make up the human body. Cord and adult stem cells are multipotent, which means that they are able to develop into more than one cell type, but they are more limited than pluripotent cells, according to NYSTEM (New York Stem Cell Science).

In the United States, cord and adult stem cells are the only ones used in regenerative medical procedures. Due to ethical controversy, embryonic stem cells are not used in clinical practice but can be used for research purposes. [How Stem Cell Cloning Works (Infographic)]

Adult stem cells

Adult stem cells — which can be taken from bone marrow, blood or fat — are mostly free of ethical controversy, but they have limited potential. As we get older, not only do our stem cells lose functionality, but we have far fewer of them. Researchers estimate that newborns have 40 times more stem cells in their bone marrow compared to a 50 year old, according to a 2009 study in the Journal of Pathology. In addition, adult stem cells may be subject to DNA abnormalities caused by sunlight, toxins and errors associated with making more DNA copies over the course of a lifetime, according to the National Institutes of Health (NIH).

Cord stem cells

Cord stem cells can be harvested from the umbilical cord after birth with the mother's permission. This tissue, which is typically discarded, can be donated to science for use in research or medicine, or placed in a cord bank in case the mother or child may need it one day.

Cord stem cells are much more efficient at replicating once removed from the body compared to adult stem cells. For example, when placed in a petri dish with the proper nutrients, one cord stem cell will multiply into 1 billion cells in 30 days, whereas one adult stem cell will multiply into only around 200 cells in 30 days, according to a 2011 study published in the journal Orthopedics.

Doctors use cord stem cells to treat autoimmune conditions, such as lupus, rheumatoid arthritis and multiple sclerosis, as well as chronic infections such as HIV, herpes and Lyme disease, according to AMA.

Embryonic stem cells

Embryonic stem cells hold the most promise for treating diseases, but heated debate abounds over the ethics of using them. Human embryonic stem cells are derived from eggs fertilized in vitro (outside of the body) and are somewhat pristine. These pluripotent stem cells are prized for their flexibility in being able to morph into any human cell.

When embryonic stem cells are grown in a laboratory under certain conditions for several months, they can remain unspecialized and produce millions of stem cells indefinitely. The resulting batch of cells is referred to as a stem-cell line.

The NIH said 64 embryonic stem-cell lines existed as of August 2001 when President Bush announced the federal policy describing the constraints on funds for stem-cell research. In March 2009, however, President Obama officially removed the restrictions placed by President Bush on federal funding for research on embryos. Although it's been contested, the policy remains in effect with strict guidelines in place by the NIH.

Induced pluripotent stem cells

Scientists can now reprogram adult stem cells to become more like embryonic stem cells. These are known as induced pluripotent stem cells (iPSCs). But since iPSCs are still adult stem cells, they carry the risk of having abnormalities. Much more research is needed on iPSCs, but scientists hope to use them in transplantation medicine, according to the NIH.

Additional resources:

• Nine things to know about stem cell treatments, from the International Society for Stem Cell Research.
• Learn about donating stem cells, from the American Cancer Society.
• Read more about the power of stem cells, from the California Institute for Regenerative Medicine.

This article was updated on April 15, 2019 by Live Science Contributor Traci Pedersen.

A mesmerizing 6-minute time lapse shows a single cell dividing seemingly endlessly until what was once a yellow blob has become a wriggling, darting salamander tadpole. 

"I wanted to film the origin of life," said Jan van IJken, a a photographer and filmmaker based in the Netherlands who created the recently released short, called "Becoming."

But what exactly is happening in this film? Live Science called a developmental biologist to learn more. [Photos: Bizarre Frogs, Lizards and Salamanders]

Van IJken was smart to choose an amphibious alpine newt. "You can look straight into the egg," he told Live Science. "They are transparent, and you can see the whole process." So, he contacted a salamander breeder and picked up a few dozen fertilized eggs.

But there are only a few hours between fertilization and the first cell division, so van IJken had to race home and, like a microsurgeon, unfurl and unglue each egg from the leaf where the salamander mother had carefully stuck it. "Sometimes, I was just in time," van IJken said.

Then, he placed the eggs in water-filled petri dishes and took thousands of photos using a camera attached to a microscope for the next four weeks.

In that initial shot, you can see the fertilized egg (also called an embryo) in the clear, protective vitelline membrane, said Lionel Christiaen, an associate professor of biology at New York University, who wasn't involved with the film. This membrane "helps keep the egg moist and prevents pathogens from getting in," Christiaen told Live Science.

Then, the embryo divides like a maniac. Rather than expanding in size, the embryo increases its number of cells with every division, all within in that same amount of space. There is a lag as each cell replicates the genetic material within it and then divides, in a process called mitosis, Christiaen said.

At about the minute mark in the film, a "hole" appears in the embryo. The process that creates the hole is called gastrulation, when the embryo organizes itself into three distinct cell layers. The importance of gastrulation was captured by Lewis Wolpert, a retired developmental biologist, who famously said, it's "not birth, marriage or death, but gastrulation which is truly the most important time in your life."

At the gastrulation stage, the embryo consists of thousands of cells, and some already "know" that they, or their progeny, will become brain cells, gut cells or something else. "But many of these cells are still on the outside of the egg," Christiaen said. During gastrulation, cells move around, organizing themselves by going to the outermost layer, or ectoderm (nervous system, skin cells and pigment cells); the mesoderm (gut, muscles and red blood cells); or the inner layer, or endoderm (lung cells, thyroid cells and pancreatic cells).

At about the 1:50 mark, the embryo looks like it's putting on a coat. This process is known as neurulation, Christiaen said, and it happens as the neural tube rolls up. After this step, almost everything on the outside of the embryo is there to stay. This consists mostly of the organism's protective skin. [In Photos: How Snake Embryos Grow a Phallus]

At about 3 minutes into the video, you can see the limb buds forming. Soon enough, you can distinguish the head from the tail. Van IJken stopped taking photos for the time lapse and switched to video as soon as the embryo moved, he noted.

Shortly after that, a tube that eventually becomes the heart begins to form, Christiaen said. And once the heart beats, blood flows. You can even see the blood flowing through the gills, the structures that help the animal with gas exchange so that it can breathe underwater.

The developing salamander twitches as it gets older, likely because its growing brain is learning how to control the animal's muscles, Christiaen said.

Finally, the yellow tadpole breaks free from the protective membrane. It's unclear how the animal knows when to do this, but hormones could play a role, Christiaen said. "There's no satisfying answer" to that question, he said.

Watching the tadpoles hatch "was incredible" van IJken said. "How this internal clockwork makes the whole thing come to life, it's incredible. It's a true miracle, one cell dividing and then becoming this animal."

And the circle of life continues, he noted. After the tadpoles hatched, van IJken gave them back to the breeder and got to work editing the film.

Editor's note: You can also see "Becoming" on Jan van IJken's Vimeo page.

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Originally published on Live Science.

Men who smoke marijuana may have higher sperm counts than those who have never used the drug, a surprising new study suggests.

The findings are "not consistent" with previous research, which has suggested that marijuana has a harmful effect on men's testicular function, the researchers said.

However, the study, published in the Feb. 6 issue of the journal Human Reproduction, doesn't mean men should start smoking pot to up their sperm counts.

The findings are far from conclusive, and more research is needed to understand whether smoking marijuana could indeed, at certain levels, have a positive effect on sperm production.

But the study does highlight how little researchers know about the effects of marijuana on reproductive health, study senior author Dr. Jorge Chavarro, an associate professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health in Boston, said in a statement. "We know a lot less than we think we know." [25 Odd Facts About Marijuana]

Marijuana and sperm

Previous studies had suggested that smoking marijuana may lower a man's sperm count, especially among heavy users. For example, in 2015, researchers from Denmark found that men who smoked marijuana more than once per week had sperm counts that were nearly 30 percent lower than those who didn't smoke marijuana, or those who used the drug less frequently.

However, the effects of more moderate marijuana use on sperm counts among men is less clear.

In the new study, the researchers analyzed information from 662 men who, along with their partners, were evaluated for infertility from 2000 to 2017 at the Massachusetts General Hospital Fertility Center. The men answered survey questions about how often they smoked marijuana or used other drugs, and they also provided sperm and blood samples.

Overall, a little over half of the men (55 percent) reported ever smoking marijuana in their lifetimes, and 11 percent said that they currently smoked marijuana.

The researchers found that men who reported ever having smoked marijuana had an average sperm concentration of 63 million sperm per milliliter of semen, compared with 45 million sperm per milliliter of semen among those who had never used marijuana. The findings held even after the researchers took into account some factors that could have affected sperm concentration, such as age, cigarette smoking and alcohol use.

What's more, only 5 percent of the marijuana smokers had lower-than-normal sperm concentrations — that is, lower than 15 million sperm per milliliter of semen. Among men who never smoked marijuana, 12 percent had lower-than-normal sperm concentrations.

Among men who had ever smoked marijuana, those who used it more often had higher testosterone levels than those who used it less often.

Interestingly, each additional year that had passed since a man last used marijuana was tied to a slight increase in sperm count.

"Our findings were contrary to what we hypothesized at the start of the study," study lead author Feiby Nassan, a postdoctoral research fellow at the Harvard T.H. Chan School of Public Health, said in the statement.

But the study can be interpreted in several ways. It may be that low or moderate levels of marijuana use have a beneficial effect on sperm production, but heavier use reverses this effect. Or, it could also be that men with higher testosterone levels are more likely to engage in "risky" behaviors such as drug use; and the researchers found the link between marijuana and sperm count "because men with higher testosterone, within normal levels, have higher sperm counts and are more likely to smoke cannabis," Nassan said.

Jury still out

It's known that moderate- to heavy-use of tobacco or alcohol is tied to lower sperm counts, but whether marijuana has the same effect is up for debate, said Dr. Sarah Vij, a urologist at the Cleveland Clinic who was not involved with the study.

Vij said she applauded the study authors for looking at this question, since it is a topic that needs more research.

But the new study doesn't provide a conclusive answer. "Overall, the jury is still out on how marijuana impacts a man's fertility potential," Vij told Live Science.

Vij pointed out that both marijuana users and nonusers in the study had normal sperm counts, on average. So the study can't draw any conclusions about whether marijuana use is tied to better fertility.

In addition, it takes about three months for men to undergo a full cycle of sperm production to produce mature sperm. This means that using marijuana years ago "really should not have any impact at all on [a man's] current fertility state," Vij said.

And yet, the study still found that men who said they used marijuana at least a year ago had higher sperm counts than men who used it more recently. Vij said she wondered if "there's something that goes along with marijuana use" that's tied to better sperm production.

The researchers also noted that their study was conducted among men who visited a fertility clinic, and so the results may not necessarily apply to the general population. In addition, men in the study self-reported their marijuana use, and it's possible that some participants were not truthful about their marijuana use, due to the social stigma or illegal status of the drug in Massachusetts at the time the data was collected.

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Originally published on Live Science.

For the first time, researchers have directly created mice with two dads.

The mice weren't able to survive for more than a day or so after birth, but coaxing an embryo made from the DNA of two dads all the way through fetal development was no small feat. It was much harder, the researchers found, than making mice with two moms.

The findings help explain why mammals can't reproduce with only a single parent. They also may help explain why those animals that can reproduce alone, such as some amphibians, are almost always female. [10 Amazing Things Scientists Just Did with CRISPR]

The barrier to single-sex reproduction, said senior study author Wei Li, a stem-cell researcher at the Chinese Academy of Sciences, is something called genomic imprinting, or the molecular tagging of DNA that regulates how the instructions in the genome are carried out. But the new study, published online Oct. 11 in the journal Cell Stem Cell, reveals that the barrier can be crossed.

Parental imprints

Genomic imprinting is known to be important for embryonic development, but exactly how it works and what controls it is a "black box," said Mellissa Mann, a researcher in reproductive science at the University of Pittsburgh School of Medicine and the Magee-Women's Research Institute who was not involved in the new study.

In sexual reproduction, every offspring inherits half its DNA from its mom, and half from its dad. But the DNA from each parent has unique molecular tags that are added during the formation of the original sperm and egg. These tags are the instructions that dictate whether a gene is expressed or stays dormant.  

"You could inherit a copy of a specific gene from mom, and that gene with these molecular 'marks' would enable it to be transcribed to do its function," Mann said. "But the same gene from dad would have different tags, preventing it from being expressed."

These tags have a lot of real-world consequences. They're crucial in early embryonic development, Mann said. Previous studies have found that when scientists try to engineer offspring from two sperm, the embryo fails to develop, while the cells that grow the placenta flourish; offspring from two eggs result in a developing embryo and a placenta that fails to grow. [5 Reasons the Placenta Is Amazing]

There are also genetic disorders that depend on genomic imprinting. Angelman syndrome, a neurological disorder that causes intellectual disability and seizures, is caused by a mutation of the UBE3A gene on the mother's chromosome. When that same gene mutation is passed down by dad instead of mom, the result is a completely different neurological disorder called Prader-Willi syndrome.

It takes two

Some animals are capable of reproducing solo. Most of these cases are when a female reproduces without a male, a process called parthenogenesis. Various fish, reptiles and amphibians can reproduce this way. Only one fish (Danio rerio) is known to reproduce with males alone, and only in certain laboratory conditions, said Baoyang Hu of the Chinese Academy of Sciences, another senior author of the new paper.

The researchers behind the new study wanted to understand why mammals can't reproduce alone. So to start, they set out to see what it takes to create parthenogenesis in mammals. They used mouse stem cells engineered to have only one set of maternal chromosomes, like an egg, and injected them into a normal egg cell to create an embryo with two sets of maternal DNA. They then transferred the resulting embryo into a surrogate mother.

To create a viable embryo, the researchers had to delete three imprinted segments of the genome from the engineered stem cells. The resulting mice appeared normal, though Li told Live Science that the mice were tested for only a limited time under experimental conditions, and so they may not have been as healthy as mice produced the old-fashioned way.

But mice with two moms are nothing new; similar mice with two moms were first produced in 2004, the authors wrote. [How Do Ancestry DNA Tests Really Work?]

So, they turned to a harder problem: Making mice with two dads. That's been done only once, by researchers at M.D. Anderson Cancer Center in Texas. In that case, researchers created male stem cells with X but no Y chromosomes, injected them into female blastocysts, the early stage of development in which some cells have differentiated into specific types. They then let those females develop into adults. They then mated the females carrying only male X-DNA with males, creating offspring that carried only genes from two dads. 

Dads alone

This time, the researchers wanted to see if they could make mice with two dads without the intermediary step of a genetically engineered female, Hu told Live Science. To do so, they injected a sperm cell and stem cells with only paternal DNA into an egg cell that had its nucleus (and thus all its maternal DNA) removed. They then extracted stem cells, which are capable of becoming any cell in the body, that developed in the resulting embryo. Those stem cells were then put into a separate blastocyst. The blastocyst was necessary to develop a placenta, Hu said. Finally, this stem-cell-injected blastocyst was put into the uterus of a surrogate mother.

"To our knowledge, it is the first time that bi-paternal mice with two direct fathers have been produced," Hu told Live Science.

But the mice didn't fare well. Indeed, successful births were in the minority. Of 1,023 attempts, only 12 live pups were born. And the pups weren't normal. They were swollen with fluids and more than twice as big as regular mice pups. All of them struggled to nurse and breathe and died soon after birth.

"People are getting ahead of the science with this to say there's a potential that two males could potentially have a child," Mann told Live Science.  "This is a very long ways off."

What the study does do, however, is hint at why parthenogenesis is more common in nature than male-only reproduction. The researchers had to delete seven imprinted regions of the genome to make male-only reproduction work, four more than they had to delete for females. (The additional loss of genetic material could explain why the mice with two fathers were so abnormal, Mann said.)

In the future, the method can be used to more closely study the effects of imprinting on various developmental disorders, said study senior author Qi Zhou, also of the Chinese Academy of Sciences. The mice could be used to test genetic modifications that might correct inherited disorders, Zhou said.

Originally published on Live Science.

All cells arise from other cells through the process of cell division. Meiosis is a specialized form of cell division that produces reproductive cells, such as plant and fungal spores and sperm and egg cells.

In general, this process involves a "parent" cell splitting into two or more "daughter" cells. In this way, the parent cell can pass on its genetic material from generation to generation.

Eukaryotic cells and their chromosomes

Based on the relative complexity of their cells, all living organisms are broadly classified as either prokaryotes or eukaryotes. Prokaryotes, such as bacteria, consist of a single cell with a simple internal structure. Their DNA floats freely within the cell in a twisted, thread-like mass called the nucleoid.

Animals, plants and fungi are all eukaryotes. Eukaryotic cells have specialized components called organelles, such as mitochondria, chloroplasts and the endoplasmic reticulum. Each of these performs a specific function. Unlike prokaryotes, eukaryotic DNA is packed within a central compartment called the nucleus.

Within the eukaryotic nucleus, long double-helical strands of DNA are wrapped tightly around proteins called histones. This forms a rod-like structure called the chromosome.

Cells in the human body have 23 pairs of chromosomes, or 46 in total. This includes two sex chromosomes: two X chromosomes for females and one X and one Y chromosome for males. Because each chromosome has a pair, these cells are called "diploid" cells.  

On the other hand, human sperm and egg cells have only 23 chromosomes, or half the chromosomes of a diploid cell. Thus, they are called "haploid" cells.

When the sperm and egg combine during fertilization, the total chromosome number is restored. That's because sexually reproducing organisms receive a set of chromosomes from each parent: a maternal and paternal set. Each chromosome has a corresponding pair, orhomolog.

Mitosis vs. meiosis

Eukaryotes are capable of two types of cell division: mitosis and meiosis

Mitosis allows for cells to produce identical copies of themselves, which means the genetic material is duplicated from parent to daughter cells. Mitosis produces two daughter cells from one parent cell.

Single-celled eukaryotes, such as amoeba and yeast, use mitosis to reproduce asexuallyand increase their population. Multicellular eukaryotes, like humans, use mitosis to grow or heal injured tissues.

Meiosis, on the other hand, is a specialized form of cell division that occurs in organisms that reproduce sexually. As mentioned above, it produces reproductive cells, such as sperm cells, egg cells, and spores in plants and fungi.

In humans, special cells called germ cells undergo meiosis and ultimately give rise to sperm or eggs. Germ cells contain a complete set of 46 chromosomes (23 maternal chromosomes and 23 paternal chromosomes). By the end of meiosis, the resulting reproductive cells, or gametes, each have 23 genetically unique chromosomes.

The overall process of meiosis produces four daughter cells from one single parent cell. Each daughter cell is haploid, because it has half the number of chromosomes as the original parent cell.

"Meiosis is reductional," said M. Andrew Hoyt, a biologist and professor at Johns Hopkins University.  

Unlike in mitosis, the daughter cells produced during meiosis are genetically diverse. Homologous chromosomes exchange bits of DNA to create genetically unique, hybrid chromosomes destined for each daughter cell.

A closer look at meiosis

Before meiosis begins, some important changes take place within the parent cells. First, each chromosome creates a copy of itself. These duplicated chromosomes are known as sister chromatids. They are fused together and the point where they are joined is known as the centromere. Fused sister chromatids roughly resemble the shape of the letter "X."

Meiosis occurs over the course of two rounds of nuclear divisions, called meiosis I and meiosis II, according to Nature Education's Scitable. Furthermore, meiosis I and II are each divided into four major stages: prophase, metaphase, anaphase and telophase.

Meiosis I is responsible for creating genetically unique chromosomes. Sister chromatids pair up with their homologs and exchange genetic material with one another. At the end of this division, one parent cell produces two daughter cells, each carrying one set of sister chromatids.

Meiosis II closely resembles mitosis. The two daughter cells move into this phase without any further chromosome duplication. The sister chromatids are pulled apart during this division. A total of four haploid daughter cells are produced during the course of meiosis II.

Meiosis I

The four stages of meiosis Iare as follows, according to "Molecular Biology of the Cell." (Garland Science, 2002):

Prophase I: At this stage, chromosomes become compact, dense structures and are easily visible under the microscope. The homologous chromosomes pair together. The two sets of sister chromatids resemble two X's lined up next to each other. Each set exchanges bits of DNA with the other and recombines, thus creating genetic variation. This process is known as crossing over, or recombination.

Even though in humans the male sex chromosomes (X and Y) are not exact homologs, they can still pair together and exchange DNA. Crossing over occurs within only a small region of the two chromosomes.

By the end of prophase I, the nuclear membrane breaks down.

Metaphase I: The meiotic spindle, a network of protein filaments, emerges from two structures called the centrioles, positioned at either end of the cell. The meiotic spindle latches onto the fused sister chromatids. By the end of metaphase I, all the fused sister chromatids are tethered at their centromeres and line up in the middle of the cell. The homologs still look like two X's sitting close together.

Anaphase I: The spindle fibers start to contract, pulling the fused sister chromatids with them. Each X-shaped complex moves away from the other, toward opposite ends of the cell.

Telophase I: The fused sister chromatids reach either end of the cell, and the cell body splits into two.

Meiosis I results in two daughter cells, each of which contains a set of fused sister chromatids. The genetic makeup of each daughter cell is distinct because of the DNA exchange between homologs during the crossing-over process.

Meiosis II

"Meiosis II looks like mitosis," Hoyt told Live Science. "It's an equational division."

In other words, by the end of the process, the chromosome number is unchanged between the cells that enter meiosis II and the resulting daughter cells.

The four stages of meiosis II are as follows, according to “Molecular Biology of the Cell, 4th edition.”

Prophase II: The nuclear membrane disintegrates, and meiotic spindles begin to form once again.

Metaphase II: The meiotic spindles latch onto the centromere of the sister chromatids, and they all line up at the center of the cell.

Anaphase II: The spindle fibers start to contract and pull the sister chromatids apart. Each individual chromosome now begins to moves to either end of the cell.

Telophase II: The chromosomes reach opposite ends of the cell. The nuclear membrane forms again, and the cell body splits into two

Meiosis II results in four haploid daughter cells, each with the same number of chromosomes. However, each chromosome is unique and contains a mix of genetic information from the maternal and paternal chromosomes in the original parent cell.

Why is meiosis important?

Proper “chromosomal segregation,” or the separation of sister chromatids during meiosis I and II is essential for generating healthy sperm and egg cells, and by extension, healthy embryos. If chromosomes fail to segregate completely, it's called nondisjunction and can result in the formation of gametes that have missing or extra chromosomes, according to "Molecular Biology of the Cell, 4th edition."

When gametes with abnormal chromosome numbers fertilize, most of the resulting embryos don't survive. However, not all chromosomal abnormalities are fatal to the embryo. For example, Down syndrome occurs as a result of having an extra copy of chromosome 21. And, people with Klinefelter syndrome are genetically male but have an extra X chromosome.

The most significant impact of meiosis is that it generates genetic diversity, and that's a major advantage for species survival.

"Shuffling the genetic information allows you to find new combinations which will perhaps be more fit in the real world," Hoyt said. 

Men's testes were once thought to be free of bacteria, but a small new study from Italy suggests that microorganisms may live naturally in this part of the male reproductive system.

What's more, the findings suggest that this so-called testicular microbiome may be different in men with a type of infertility called azoospermia, who have no measurable sperm in their semen, than it is in fertile men.

Still, the findings are very preliminary, and much more research is needed to confirm if the testicular microbiome actually affects sperm production, the researchers said. But if the findings hold up, studies on the testicular microbiome might one day lead to the development of new therapies for men with azoospermia, who currently have few treatment options, experts say. [Trying to Conceive: 12 Tips for Men]

"These findings are actually surprising, because almost all medical textbooks mention that [the] human testes … is a microbiologically sterile microenvironment," said study lead author Massimo Alfano, a senior scientist at the Urological Research Institute at the IRCCS Hospital San Raffaele in Milan. But with new technologies, "for the first time ever, we [have] been able to quantify the bacterial DNA" in the testes, Alfano told Live Science.

"If confirmed and expanded, these results could support future … therapies for male factor infertility" such as those based on restoring a proper "testicular niche," Alfano said.

The study was published May 30 in the journal Human Reproduction.

Testicular microbiome

About 1 percent of all men, and 10 to 15 percent of men with infertility, have azoospermia, according to the Cleveland Clinic. Couples in which the man has azoospermia cannot become pregnant naturally, because there is no sperm in the man's ejaculate, said Dr. Sarah Vij, a urologist at the Cleveland Clinic who was not involved with the study.

"Those are the men that we really want to be able to help the most," Vij said, referring to men with azoospermia. "Some of those men [with azoospermia] have no options to have a biological child."

The most severe form of azoospermia is "non-obstructive azoospermia," which means the condition results from poor sperm production, rather than a blockage that prevents sperm from getting into the semen. The only treatment option for non-obstructive azoospermia is a surgery that attempts to retrieve sperm from the testicular tissue, which is not always successful, Vij told Live Science.

For the new study, the researchers analyzed testicular tissue from 10 men with non-obstructive azoospermia, as well as testicular tissue from five men without azoospermia who produced normal amounts of sperm. Among the men with azoospermia, half had successful surgeries that retrieved sperm, while half had unsuccessful surgeries that didn't retrieve any sperm.

The researchers found that the men without azoospermia had small amounts of bacteria in their testes, and these bacteria belonged to four main groups, called Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria.

The men with azoospermia had more bacteria overall in their testes, but their testicular microbiome was less diverse: The researchers found only two groups of bacteria — Actinobacteria and Firmicutes — in these men. What's more, the men who didn't have sperm retrieved during surgery had even less diversity in their microbiome, which was dominated mainly by Actinobacteria.

Avoiding surgery?

"I definitely applaud what they've done," Vij said of the study. "I think it has potential significance."

Currently, doctors do not have a way to predict which men with azoospermia will have successful sperm retrieval from surgery, Vij said. But the new findings raise the question of whether the testicular microbiome might help predict successful sperm retrieval. "If the microbiome can enable us to predict who is going to have success, we could probably spare some men surgery," she said.

In addition, if the findings are confirmed, it's possible that the testicular microbiome "could help guide future therapies for men, to give them another option" besides surgery, Vij said.

Still, even if future studies confirm the results, there are many more steps needed before the findings could be meaningful for patients. For example, the current study used testicular biopsies to describe the microbiome, but these procedures are invasive. "We have to figure out a way to assess the microbiome noninvasively, to have meaning" for patients, Vij said.

Additional studies would also need to examine whether changing the microbiome could have an effect on sperm production, she said.

In 2016, early research also suggested that women's fallopian tubes and ovaries may have microbiomes.

Original article on Live Science.

Human sperm cells are well-studied, so scientists were completely surprised to find a previously unknown structure in the little swimmers. And perhaps more surprising, this newfound structure may contribute to infertility, miscarriages and birth defects, the investigators said.

On the flip side, once scientists understand this structure better, it may help them develop new therapies for male infertility and learn more about early human embryonic development, the researchers said.

The newly identified part is a centriole, a barrel-shaped structure made of short microtubules. Researchers already knew that sperm cells contain one centriole, but the new discovery brings the total to two centrioles per sperm. [Sexy Swimmers: 7 Facts About Sperm]

However, the newfound centriole has a slightly different structure than the previously known one, so the researchers are calling it atypical in shape.

"This research is significant because abnormalities in the formation and function of the atypical centriole may be the root of infertility of unknown cause in couples who have no treatment options available to them," study researcher Tomer Avidor-Reiss, a professor in the Department of Biological Sciences at the University of Toledo in Ohio, said in a statement. "It also may have a role in early pregnancy loss and embryo development defects."

Previously, researchers thought that sperm carried just one centriole, which then duplicated itself if the sperm met an egg. That's because the egg does not have a centriole, while a zygote — or a fertilized egg — needs two centrioles to start the development of a fetus, the researchers said.

These centrioles play a pivotal role. They are needed for building the cell's cytoskeleton (the structure that maintains cell shape) and completing accurate cell division, the researchers noted.

By learning how centrioles work during the early stages of reproduction, scientists may be able to pinpoint if these structures are involved with any type of male infertility or later problems with the developing embryo.

"Since the mother's egg does not provide centrioles and the father's sperm possesses only one recognizable centriole, we wanted to know where the second centriole in zygotes comes from," Avidor-Reiss said. "We found the previously elusive centriole using cutting-edge techniques and microscopes. It was overlooked in the past, because it's completely different from the known centriole in terms of structure and protein composition."

This isn't the only recently uncovered structure in human sperm. Earlier this year, researchers announced the discovery of a mysterious spiral in the tail of human sperm; this structure may give the sperm a boost while it's swimming, Live Science previously reported.

The new study was published online June 7 in the journal Nature Communications.

Original article on Live Science.

Miles beneath the ocean's surface, in the darkened waters along a rocky seafloor, a submersible vehicle unexpectedly encountered a bizarre spectacle: hundreds of small, purple octopuses, many of them mothers protecting clusters of eggs, clinging to the hardened lava from an undersea volcano.

The sight was astonishing, researchers said. During multiple dives, the submersible's cameras captured as many as 100 octopuses at a time, most clutching broods of eggs attached to the rocky outcrop, clustered around cracks in the cooled lava substrate.

The octopuses, which sport enormous eyes in comparison to their dinner plate-size bodies, were identified as a new species in the genus Muuscoctopus. That made the sightings even stranger, as octopus in that group are usually loners that don't gather in dense communities. [8 Crazy Facts About Octopuses]

Things got weirder from there. Water temperatures where the colony huddled were much warmer than is suitable for deep-sea octopuses, which have trouble extracting oxygen from water that's too hot. In fact, researchers who investigated the colony found that none of the embryos were developing and reported in a new study that the adults were "unlikely to survive."

What's the story behind this mysterious, doomed gathering of octopus mothers, huddling uncomfortably in volcano-warmed waters and guarding eggs that will never hatch?

"They shouldn't be there"

"When I first saw the photos, I was like, 'No, they shouldn't be there! Not that deep and not that many of them,'" study co-author Janet Voight, an associate curator of zoology at the Field Museum of Natural History in Chicago, said in a statement released by the museum.

The tale unfolded on the Dorado Outcrop, located about 155 miles (250 kilometers) west of Costa Rica at a depth of 9,842 feet (3,000 meters). Study co-author Geoff Wheat, a geochemistat the University of Alaska Fairbanks, led two expeditions to the outcrop — in 2013 and 2014 — recording photos and hundreds of hours of video of the unusual octopus gathering.

During the dives, the researchers collected data on water temperature and evaluated the amount of dissolved oxygen in the water. They also observed 606 octopuses (though some may have been counted multiple times, the researchers said). The animals' smooth skin, the two rows of suckers on their arms and their brooding postures identified them as members of the Muuscoctopus genus.

However, the scientists collected no individuals, and the newfound species remains undescribed, according to the study. [Octlantis: See Photos of Tight-Knit Gloomy Octopus Communities]

A recipe for disaster

But what were so many octopuses doing in that location? It's highly unlikely that they were drawn to the area because it was a desirable place to lay eggs, the scientists said. Though prior research has shown that elevated water temperatures can speed up egg development, the heat also increases octopuses' metabolic rate, which makes them need more oxygen. And the water seeping from cracks in the rocky outcrop carried just half as much oxygen as the water in the surrounding areas, the study authors wrote.

Together, those factors would spell disaster for mothers and eggs, generating stress levels that could be severe — and likely even lethal, the scientist said. 

Perhaps, however, conditions around the rocks weren't so dire when the mothers initially attached their eggs, the researchers suggested. The flow of warmed, oxygen-poor liquid may have been weaker or not even present when the octopuses first arrived, but then, once their eggs were in place, they didn't want to abandon them.

It's also possible that these individuals were forced to relocate into an undesirable neighborhood because of overcrowding in cooler, more-hospitable parts of the rocky outcrop. In this scenario, the females would simply have had no choice but to move to the hotter, low-oxygen area to lay their eggs, the scientists reported.

Given that this group of stressed octopus moms was so large, it would make sense that an even bigger population was thriving nearby, Voight suggested in the statement.

"Octopus females only produce one clutch of eggs in their lives. In order for this huge population to be sustained, there must be even more octopuses to replace the dying mothers and eggs that we can see," Voight said.

Wheat and the study's lead author Anne Hartwell, an oceanographer affiliated with Ohio's University of Akron and the University of Alaska Fairbanks, even reported seeing octopus arms extending from within cracks in the outcrop, suggesting that octopuses could have been lurking in cavities inside those cracks, where the water was cooler and more oxygen-rich, Voight added.

For now, the mystery of the doomed octopus nursery remains unsolved. But finding the gathering gave researchers an exciting glimpse of previously unseen octopus behavior, along with a reminder of how much scientists have yet to learn about life in the unexplored ocean depths, Wheat said in the statement.

"This is only the third hydrothermal system of its type that has been sampled, yet millions of similar environments exist in the deep sea," Wheat said. "What other remarkable discoveries are waiting for us?"

The findings were published online March 28 in the journal Deep Sea Research Part I: Oceanographic Research Papers.

Original article on Live Science.

Researchers who have been observing migrating North Atlantic right whales, which are endangered, are troubled by what they found this season: no sign of any newborns.

The North Atlantic right whale (Eubalaena glacialis) — one of three right whale species, along with the Southern and Pacific right whales, defined by the ocean ranges they inhabit — typically reproduce during the winter months, which they spend in waters off the southeastern coast of the U.S. But this year, the season is winding to a close without any sightings of new babies — something that hasn't happened in nearly three decades of aerial observations, the Associated Press (AP) recently reported.

During the species' reproductive season, the North Atlantic right whale populations average about 17 births per year. Though the number of births has been below average since 2012, the prospect of zero new births this season is "truly alarming," Phillip Hamilton, a researcher with the New England Aquarium in Boston, told the AP. [Whale Photos: Giants of the Deep]

Calving season for these whales begins in mid-November and lasts until around mid-April. At the season's start, the pregnant females migrate 1,000 miles (1,600 kilometers) from northern waters near New England and Canada to their winter homes in warmer waters near Georgia, South Carolina and the eastern coast of Florida, representatives of the National Oceanic and Atmospheric Administration (NOAA) said in a statement released in November.

Every winter since 1989, research planes staffed by NOAA experts have taken to the air and flown over the open ocean to observe the whales and count the adults and new additions swimming near their mothers, NPR reported in February.

But this year, the researchers spotted no new calves at all. And now, with the season nearly at an end, the grim reality is that there likely are none, Barb Zoodsma, a right whale biologist for NOAA Fisheries, told the AP.

The North Atlantic right whale is one of the rarest marine mammals in the world, and right now, their prospects are not looking promising. Approximately 450 of them are left in the wild, and there were 16 reported whale deaths in this species during the summer of 2017 — a record number for a six-month-period — according to the NOAA statement.

Of the 450 whales, only about 105 are breeding females, NOAA reported in the statement. Producing fewer calves — or none at all — means that their dwindling numbers won't be replenished, and the populations will eventually die out.

"It's a pivotal moment for right whales," Zoodsma said. "If we don't get serious and figure this out, it very well could be the beginning of the end."

Original article on Live Science.

The reproductive system is a collection of internal and external organs — in both males and females — that work together for the purpose of procreating, according to the Cleveland Clinic. Due to its vital role in the survival of the species, many scientists argue that the reproductive system is among the most important systems in the entire body.

How reproductive systems work

The male reproductive system consists of two major parts: the testes, where sperm are produced, and the penis, according to Merck Manuals. The penis and urethra belong to both the urinary and reproductive systems in males. The testes are carried in an external pouch known as the scrotum, where they normally remain slightly cooler than body temperature to facilitate sperm production. 

• Related: Probiotics for vaginal health

The external structures of the female reproductive system include the clitoris, labia minora, labia majora and Bartholin's glands, according to the Cleveland Clinic. The major internal organs of the female reproductive system include the vagina and uterus — which act as the receptacle for semen — and the ovaries, which produce the female's ova. The vagina is attached to the uterus through the cervix, while the fallopian tubes connect the uterus to the ovaries. In response to hormonal changes, one ovum, or egg — or more in the case of multiple births — is released and sent down the fallopian tube during ovulation. If not fertilized, this egg is eliminated during menstruation.

Fertilization occurs if a sperm enters the fallopian tube and burrows into the egg. While the fertilization usually occurs in the oviducts, it can also happen in the uterus itself. The egg then becomes implanted in the lining of the uterus, where it begins the processes of embryogenesis (in which the embryo forms) and morphogenesis (in which the fetus begins to take shape). When the fetus is mature enough to survive outside of the womb, the cervix dilates, and contractions of the uterus propel it through the birth canal. 

Variations in the reproductive system

Around 49.5 percent of the world's population is female, so there are slightly more men on the planet than women, according to World Bank. A person's sex is determined by what reproductive system the person has, but it isn't always so simple. Some humans are born with parts of both male and female reproductive systems or incomplete reproductive organs of one sex or the other. Those with both male and female reproductive parts are considered intersex. Sometimes children are labeled as male or female, depending on how complete or functional one sexual reproductive system is over the other. Then, the other organs are removed. 

Today, many parents are opting to leave both sets of reproductive organs intact with the intent of letting the child decide to keep or remove the various parts when they are older. A baby is born atypical genitalia in one in about 1,500 to 2,000 births, according to Intersex Society of North America. 

Females that are born without all of their reproductive system are labeled as having Mayer Rokitansky Kuster Hauser Syndrome. This occurs in one in 5,000 female births, according to the Center for Young Women’s Health. 

Diseases of the female reproductive system

Many parts of the male and female reproductive systems can be affected by cancer. In females, cancer can attack the uterus, ovaries, breast and cervix, among other organs, according to the American Cancer Society. 

Many experts have seen what they refer to as the "Angelina Jolie" effect, where women are taking proactive measures by having breasts and internal reproductive organs removed if they have a family history of cancer before there are signs of the disease. "With better genetic testing and screening, we have seen a number of women who are being more proactive about their reproductive health," said Dr. Shana Wingo, who specializes on gynecologic oncology at Arizona Oncology. 

Ovarian cancer tends to have a poorer outcome than other gynecological cancers, Ross noted, because it is not typically diagnosed until it has progressed significantly. "There is no standard screening available for ovarian cancer, so it is very difficult to identify it early." 

Tests to detect ovarian cancer, as well as cancer of the fallopian tube, and primary peritoneal cancer are currently being studied, according to the National Cancer Institute. 

There are two tests used to screen for cervical cancer. The Pap test screens for cellular changes in the cervix called cytology, while the genital human papillomavirus (HPV) test identifies the presence of infection with high-risk HPV, the strains that are linked to cervical cancer, according to Dr. Charles Dubin, an OB/GYN in Santa Monica, Calif.

A recent study published by Cancer Cytopathology, found that HPV-only screening misses more cervical cancer in women than Pap-only or co-testing, based on approximately 8.6 million women ages 30 to 65. There is approximately a three-fold improvement in the cancer detection rate of co-testing compared to HPV only.

Current guidelines recommend that women first start getting the Pap test alone when they turn 21 and repeat every three years if the test is normal until age 30. A Pap-plus-HPV test, or co-testing, is recommended for women ages 30 to 65, and if both are negative repeated every five years, regardless of whether they have received HPV vaccination. "However, there is compelling scientific evidence that co-testing every three years misses less cases of cancer and pre-cancer than every five-year co-testing," Dubin noted.

While genital HPV is typically associated with females, it is the most common sexually transmitted infection. The majority of sexually active people in the United States — male and female — will have HPV at some time in their lives, but most will not experience any symptoms. In a small portion of women, it can result in cervical cancer and genital warts; in men, it can cause penile and anal cancer and genital warts, according to the NIH.

Both genders can develop sexually transmitted diseases, including genital herpes, gonorrhea and syphilis, according to the National Institutes of Health (NIH). HIV/AIDS, a disease of the immune system, is not exclusively transmitted through sexual contact; sexual activity is one of the ways that the HIV virus is spread.

For females, severe menstrual cramping, or dysmenorrheal, is the most common disease of the reproductive system occurs with a woman's monthly menstrual period, according to Dr. Sheryl Ross, OB/GYN and Women's Health Specialist at Providence Saint John’s Health Center.

"Severe pain before or during your period can last anywhere from one to seven days and disrupt your normal day-to-day routines at school, work and socially," Ross noted. Diagnosis is made by the patient's medical history and a pelvic exam. The best treatment includes medications that block the effects of prostaglandins and include ibuprofen and naproxen. The birth control pill also works well in treating dysmenorrhea by decreasing the blood flow, Ross noted.

Another common disorder of the female reproductive system is a vaginal yeast infection, which is caused by a yeast fungus in the vagina. Most can be successfully treated with over-the-counter medications, according to WebMD. 

Endometriosis is a condition where that normally lines the inside of your uterus — the endometrium — ends up outside of uterus, most commonly in the ovaries, bowel or the tissue lining your pelvis. The endometrial tissue becomes trapped, causing pain, according to the Mayo Clinic. 

Pelvic inflammatory disease can involve an infection of any of the female reproductive organs, including the uterus and ovaries. Sexually transmitted diseases, such as gonorrhea and chlamydia, are typical causes of pelvic inflammatory disease, according to the NIH. "Any of these STIs can cause serious and potentially long term reproductive problems that include chronic pelvic pain and infertility," Ross said.

Diseases of the male reproductive system

Of male-specific diseases of the reproductive system, prostate cancer is the most common, but men can also suffer from testicular and penile cancer, according to the American Cancer Society. 

Treatment for prostate cancer depends on the age, severity of the disease and other health conditions of the patient. The usual treatments for prostate cancer are surgery, radiation therapy, watchful waiting, and hormonal treatment, according to the Cleveland Clinic. 

Erectile dysfunction is a common condition that affects about one in 10 males on a long-term basis, the Cleveland Clinic noted. It can be linked to vascular disease, neurological disorders such as Multiple Sclerosis, trauma and psychological episodes.

Prostatitis typically involves swelling or inflammation of the prostate gland, according to the Mayo Clinic, and can cause painful or difficult urination and ejaculation. Nearly half of all men experience symptoms of prostatitis at some point during their lives.

Defining and treating infertility

Infertility is defined as a couple's inability to conceive after one year of unprotected intercourse. It can be caused by a condition in one partner or a combination of circumstances, according to the Mayo Clinic.

In males, infertility is a condition in which they produce no sperm cells (azoospermia) or too few sperm cells (oligospermia), or their sperm cells are abnormal or die before they can reach the egg. Causes range from chromosomal defects to hormonal imbalance to tumors. Lifestyle factors, such as drug and alcohol use, can also play role. In rare cases, infertility in men is caused by an inherited condition, such as cystic fibrosis, according to the Mayo Clinic.

In women, infertility is defined as a disorder of the reproductive system that hinders the body's ability to ovulate, conceive, or carry an infant to term.

Reproductive conditions are treated by a variety of specialists. In women, many issues are treated by obstetricians/gynecologists and for males, urologists handle many disorders of their reproductive systems. There are also infertility experts that treat couples who are unable to conceive and endocrinologists who treat hormonal disorders.

Additional reporting by Alina Bradford, Live Science contributor.

Editor’s Note: If you’d like more information on this topic, we recommend the following book:

Systems of the human body

• Circulatory System: Facts, Function & Diseases
• Digestive System: Facts, Function & Diseases
• Endocrine System: Facts, Functions and Diseases
• Immune System: Diseases, Disorders & Function
• Lymphatic System: Facts, Functions & Diseases
• Muscular System: Facts, Functions & Diseases
• Nervous System: Facts, Function & Diseases
• Respiratory System: Facts, Function & Diseases
• Skeletal System: Facts, Function & Diseases
• Skin: Facts, Diseases & Conditions
• Urinary System: Facts, Functions & Diseases

Parts of the human body

• Bladder: Facts, Function & Disease
• Human Brain: Facts, Anatomy & Mapping Project
• Colon (Large Intestine): Facts, Function & Diseases
• Ears: Facts, Function & Disease
• Esophagus: Facts, Function & Diseases
• How the Human Eye Works
• Gallbladder: Function, Problems & Healthy Diet
• Human Heart: Anatomy, Function & Facts
• Kidneys: Facts, Function & Diseases
• Liver: Function, Failure & Disease
• Lungs: Facts, Function & Diseases
• Nose: Facts, Function & Diseases
• Pancreas: Function, Location & Diseases
• Small Intestine: Function, Length & Problems
• Spleen: Function, Location & Problems
• Stomach: Facts, Function & Diseases
• The Tongue: Facts, Function & Diseases

Additional resources

• NIH: Aging changes in female reproductive system, and in male reproductive system
• CDC: Women's Reproductive Health & Men's Reproductive Health

Scientists have spent decades studying the extraordinary abilities and anatomy of human sperm, so an international team of researchers was surprised to discover a mysterious, spiral-shaped nanostructure in the tails of sperm.

The newfound spiral may give sperm tails a boost, the scientists said.

Sperm need a highly effective tail so they can swim as fast as possible toward the egg and attempt to fertilize it. Each sperm tail has thousands of building blocks, the most important of which are called tubulins, the researchers said. These tubulins form long tubes known as microtubules in the sperm's tail. [Sexy Swimmers: 7 Facts About Sperm]

These microtubules are attached to thousands of motor proteins (proteins that can move) that pull and bend the microtubules, allowing the sperm to swim.

"It's actually quite incredible that it can work," study senior researcher Johanna Höög, a researcher in the Department of Chemistry and Molecular Biology at the University of Gothenburg, in Sweden, said in a statement. "The movement of thousands of motor proteins has to be coordinated in the minutest of detail in order for the sperm to be able to swim."

To get a better look at the sperm tail, Höög and her colleagues imaged sperm specimens with a Nobel Prize-winning microscope technique known as cryo-electron tomography, or cryo-ET. This method allows researchers to freeze tiny structures, such as sperm, and take a series of 2D pictures that can then be combined to make an incredibly detailed 3D image. Moreover, this method doesn't require any chemicals, which would obscure the smallest cell structures, Höög said.

"When we looked at the first 3D images of the very end section of a sperm tail, we spotted something we had never seen before inside the microtubules: [a] spiral that stretched in from the tip of the sperm and was about a tenth of the length of the tail," Höög said.

The researchers named the helical structure a "tail axoneme intra-lumenal spiral," or TAILS. It's still unclear exactly what TAILS does, what it's made out of and how important it is, they said. But the researchers have a few ideas they plan to study further, said lead researcher Davide Zabeo, a doctoral student in the Department of Chemistry and Molecular Biology at the University of Gothenburg.

"We believe that this spiral may act as a cork inside the microtubules, preventing them from growing and shrinking as they would normally do, and instead allowing the sperm's energy to be fully focused on swimming quickly towards the egg," Zabeo said in the statement.

Despite the surprise surrounding this finding, it's not the only recent sperm discovery. Just last year, researchers found that human sperm cells get an extra oomph when they swim, largely because of interconnected elastic springs in their tails that communicate with other regions of the tail, Live Science previously reported.

The new study was published online Feb. 9 in the journal Scientific Reports.

Original article on Live Science.

Pesticide residue on fruits and vegetables may hurt women's fertility, a new study suggests.

The study found that women who ate fruits and vegetables with relatively high levels of pesticide residue were less likely to get pregnant and give birth following fertility treatments, compared with women who ate fruits and vegetables with lower levels of pesticide residue.

The findings suggest that "dietary pesticide exposure … may be associated with adverse reproductive consequences," the researchers from the Harvard T.H. Chan School of Public Health wrote in the Oct. 30 issue of the journal JAMA Internal Medicine.

However, because the study is one of the first to show such a link, more research is needed to confirm the results, they said. [9 Disgusting Things That the FDA Allows in Your Food]

Previous studies in animals have found that ingestion of pesticide mixtures at levels thought to be safe was linked to a decrease in the number of offspring that the animals had, according to the study. But it wasn't clear if the same was true for people.

In the new study, the researchers analyzed data from 325 women who underwent treatment for infertility using assisted reproductive technology, such as in vitro fertilization (IVF). Before the women started their treatment, they completed a survey about their diet, including how often they ate certain foods.

Then, the researchers used a government database containing information on typical pesticide levels found on different types of fruits and vegetables to estimate the women's exposure to pesticides. The database showed that some fruits and vegetables, such as peppers, raw spinach and strawberries, tend to have relatively high levels of pesticide residue, and other types, such as peas, dried plums and onions, tend to have relatively low levels.

The results showed that women who ate more than two servings of high-pesticide-residue fruits and vegetables a day were 18 percent less likely to get pregnant, and 26 percent less likely to give birth, than those who ate less than one serving of high-pesticide-residue fruits and vegetables a day.

The findings held, even after the researchers took into account factors that could affect reproductive health, such as age, body mass index (BMI) and smoking habits, and whether the women said they ate organic fruits and vegetables, which tend to have lower levels of pesticide residues.

Still, the researchers noted that the study only found an association between pesticide exposure and worse reproductive outcomes, and it cannot prove a "cause and effect" relationship. The study did not directly test fruits and vegetables for pesticides, but rather, estimated the level of pesticides using a database; and it's possible that these estimates were not always accurate, the researchers said. In addition, because the women in the study were seeking treatment for infertility, it's not clear if the results apply to the general population.

As one way to reduce exposure to pesticides and other environmental chemicals, the American Congress of Obstetricians and Gynecologists recommends that women who are pregnant or trying to conceive carefully wash fresh fruits and vegetables before eating them.

A previous study from the same group of researchers also found that men who ate fruits and vegetables with high levels of pesticide residue had lower sperm counts than men who ate fruits and vegetables with low levels of pesticide residue.

Original article on Live Science.

Human women typically go through menopause between ages 45 and 55, when they undergo hormonal changes that cause them to stop being able to reproduce. But they're not the only ones in the animal kingdom who live beyond their reproductive years.

Scientists have long known that animals' fertility and reproductive success slowly decline with increasing age — a phenomenon called reproductive senescence. But, for the most part, reproduction in animals seems to continue up to old age and death, though at a diminished capacity.

In a recent review of primate species, researchers found that humans are the only primates that don't die within a few years of "fertility cessation." And this is true even when modern medicine and health care are taken out of the equation, as the study included data from the hunter-gatherer !Kung tribe in the Kalahari Desert.

In the past couple of decades, however, numerous studies have claimed that menopause, or "post-reproductive life spans" — a phrase that most often refers to the age of last reproduction, since changes in ovulation and hormones related to menopause are difficult to measure in wild animal populations — occurs in a wide range of species. Guppies, for instance, appear to go through a fish version of menopause, according to one study, which found that the fish spend an average of 13.6 percent of their total life spans in a post-reproductive stage.

In fact, such "menopause" appears somewhat common among fish, birds, mammals and invertebrates (animals without backbones), according to a recent review on the topic published in July 2015 in the journal Trends in Ecology & Evolution. Yet, there's a major caveat to this statement: For the vast majority of species, the animals don't live long after they stop reproducing, and menopause appears to be a circumstance related to captivity (such as in the guppies) that occurs only in some individuals, not the entire species.

But there are exceptions. Among vertebrates, two species of toothed whales live long lives after menopause. Female killer whales reproduce between the ages of 12 and 40 years but can survive into their 90s, while female short-finned pilot whales reproduce between the ages of 7 and 35 and live past 60.

Also in this select group are some insects, such as the gall-forming social aphid Quadrartus yoshinomiyai, in which adult females have extended post-reproductive livesdefending the colony.  

From an evolutionary standpoint, menopause is an apparent oddity, given that you'd expect individuals to want to pass on their genes for as long as possible. So why did it develop at all?

The most prevalent theory behind menopause is called the grandmother hypothesis. In short, it suggests females may stop breeding early to help their children and grandchildren survive and reproduce. This certainly appears true in orca populations, in which older females are repositories of ecological knowledge, especially when it comes to finding food — researchers found mothers increase the survival rate of their adult sons, which have better reproductive success the older they get.

Interestingly, matriarch elephants are also vital in the community, but they don't go through menopause.

The difference here lies in how the groups are made up. Killer whales' sons and daughters stay in the groups in which they were born. So, over time, the mothers become increasingly related to their neighbors, providing a motive to shift from reproducing to helping their descendants, thus further enhancing their genetic legacy. In elephant society, on the other hand, sons leave the birth group, so mothers don't become any more related to their group mates as they age.

Another key aspect of this is competition for resources.

Research in orcas shows that when two generations of killer whales in the same group breed simultaneously, calves from the older generation of females are 1.7 times more likely to die. This is possibly because younger females are focused only on their calves, whereas the older females may raise their own children and those of their adult daughters.

In ancestral humans, daughters would move out to join new families. A daughter would initially have no relation to the group until she had children, but as she got older, she would become increasingly related to her group. Eventually, helping her relatives raise their children would become more genetically beneficial to her, especially since having more children would put her new kids in direct competition for resources with her other descendants. 

Originally published on Live Science.

During recent outbreaks of the Zika virus, researchers discovered that the virus could find its way into men's semen and stay there for months. But how many other viruses can get into semen?

To find out, researchers at the University of Oxford in the United Kingdom searched the scientific literature for reports of "viremic" viruses — ones that get into the blood —  that have also been found in semen.

The results showed that at least 27 viruses can make their way into human semen.

"The presence of viruses in semen is probably more widespread than currently appreciated," the researchers wrote in the October issue of the journal Emerging Infectious Diseases. [10 Deadly Diseases That Hopped Across Species]

The list includes a number of well-known viruses, such as Ebola, HIV, hepatitis C, chickenpox, herpes, mumps and chikungunya (a mosquito-borne virus), as well as some lesser-known viruses, such as JC virus, simian foamy virus and Rift Valley fever.

In addition, some of these viruses, such as HIV and herpes, are known to spread sexually. But for many of the viruses on the list, it's unclear whether they can be spread through sex, the researchers said.

The results raise a number of questions, including how long the viruses remain in semen, at what concentrations they are present, and whether the viruses remain "viable" or capable of causing disease, the researchers said. The answers to these questions will help researchers better understand the risk for sexual spread of these viruses, the study said.

More research is also needed on whether these viruses can infect sperm, the researchers said. (Sperm are men's reproductive cells, whereas semen is usually a mixture of sperm and fluids.) This is an important question, because infections in sperm could cause mutations in the sperm DNA that might be passed on to the next generation, and possibly increase the risk of conditions such as cancer, the researchers said.

It's thought that some viruses persist in semen — even when they've been cleared from the rest of the body — because the testes are an "immunologically privileged" site in the body, meaning they are protected from attack by the body's immune system.

The findings also highlight the need for researchers to consider whether treatments being developed for virial diseases can be effective against viruses in all parts of the body, including the male reproductive tract, the researchers said.

Original article on Live Science.

A woman in Arizona who was born without a vagina — the result of a rare condition — is speaking out about her condition, and raising money for a surgery to treat it.

Kaylee Moats, who is 22, first learned she did not have a vagina when she was 18 and had never had a menstrual period, according to a video about Moats' case, made by Barcroft TV. An ultrasound performed at her doctor's office revealed that she did not have a uterus, cervix or vagina.

"It makes me feel less of a woman," Moats said in the video. "I'm still trying to accept myself, accept what I have and not dwell on it."

Moats was diagnosed with Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome, a condition that affects about 1 in every 4,500 newborn girls, according to the National Institutes of Health. It happens when, during embryonic development, the female reproductive organs (including the uterus, cervix and vagina) do not develop properly. As a result, the uterus and vagina may be underdeveloped or absent entirely, the NIH said. [7 Facts Women (And Men) Should Know About the Vagina]

People with this condition are genetically female (meaning they have two X chromosomes), and have normally functioning ovaries. They also have normal external genitalia, and so the condition is usually discovered only when women do not get their period, as was the case for Moats.

In some cases, the condition can be treated without surgery, by using vaginal "dilators" to create a vagina or enlarge an existing vagina, according to the National Organization for Rare Diseases (NORD). Vaginal dilators are specially designed plastic tubes that can be used to stretch and widen the small amount of vaginal tissue that is typically present (sometimes referred to as a vaginal "dimple"), according to NORD.

The condition can also be treated with surgery to create a vagina, which is called a vaginoplasty.

Researchers have created vaginas in a lab dish, by taking a patient's own cells and growing them on a scaffold to form a vaginal shape. In 2014, researchers announced they had implanted these vaginas in four teenage girls, and the treatment was successful. However, the treatment is still experimental.

For Moats, the next step is to have reconstructive surgery to create a vagina, she said. However, the surgery costs $15,000 and is not covered by her insurance.

"They consider it a cosmetic surgery or a gender reassignment," Moats said. "It's very hurtful" to not have this surgery covered by insurance, she said.

Moats' sister, Amanda Moats, started a GoFundMe page to raise money for the surgery. As of today (Aug. 17), she had raised $16,997, exceeding the goal of $15,000.

"Getting the surgery will help me feel normal and have all the right body parts as any other girl," Moats told Barcoft TV.

Moats has a boyfriend, Robbie Limmer, whom she met as a senior in college. Moats said Limmer has been supportive of her, and does not focus on the sexual side of their relationship.

"Knowing that he accepts me for who I am, and doesn't see me as less of a person or less of a woman, makes me feel loved," Moats said.

Moats hopes to have children someday. Because she has functioning ovaries, she can, in theory, use a gestational surrogate to carry her child.

Original article on Live Science.

A 35-year-old Florida woman had been unable to get pregnant for 14 years, but her fertility problems were resolved in a most unusual way: A chemotherapy drug that she was given after being diagnosed with cancer triggered her ovaries to function better, a new case report reveals.

The woman was diagnosed with pancreatic cancer and had surgery to remove the cancerous growth. Then, she was treated with the chemotherapy drug gemcitabine.

The gemcitabine likely restored the woman's ability to ovulate and become pregnant, according to the case report, published online (July 11) in the Journal of Medical Case Reports. [27 Oddest Medical Cases]The woman had previously been diagnosed with polycystic ovarian syndrome (PCOS), which is one of the most common causes of infertility in women, the report said. The condition is caused by an imbalance of reproductive hormones, and it interferes with the growth and release of eggs from a woman's ovaries during ovulation each month.

"Gemcitabine was the only new variable that may have changed her hormonal ratios," said Dr. Stephen J. Carlan, one of the case report authors and the director of research in the department of obstetrics and gynecology at Orlando Regional Healthcare in Orlando, Florida. For most patients with cancer, this chemotherapy drug is known to be toxic to the ovaries, he noted.

An infertility journey

Women with PCOS have irregular periods that may come infrequently, too often or not at all. This makes it challenging for them to become pregnant.

The woman in the recent case report had tried unsuccessfully to become pregnant for more than a decade. She had used fertility treatments, including taking medication to induce ovulation followed by having intercourse with her partner during her most fertile days, but these attempts failed. She had also lost weight, which is recommended for women with PCOS, because it may help them have more regular menstrual cycles, but this did not lead to conception either. 

The woman had decided not to pursue in vitro fertilization or other methods to assist her in becoming pregnant. [Conception Misconceptions: 7 Fertility Myths Debunked]

After she felt a lump on the left side of her abdomen, where she had had been experiencing sharp pain for about two months, she went to the emergency room for an evaluation. She was admitted to the hospital, where imaging scans revealed pancreatic cancer.

The cancerous growth was removed from her pancreas in a complex operation known as a Whipple procedure. Eight weeks after her surgery, the woman started on the first of four rounds of chemotherapy with gemcitabine, followed by radiation treatments.

When her cancer treatments were completed, the woman suddenly started having regular menstrual cycles, Carlan told Live Science. Then, 15 months after being diagnosed with pancreatic cancer, she received some unexpected news for someone who had struggled for years with PCOS-induced infertility: She was six weeks pregnant, but had suffered a miscarriage. 

Nearly three years after this miscarriage, the now-40-year-old woman first came to see the obstetricians who authored her case report. She was almost five months pregnant at the time.

Fertility restored

The doctors suspect that gemcitabine restored the woman's fertility by acting on her body in way similar to a treatment for PCOS: a surgical procedure called partial ovarian destruction, or "ovarian drilling," Carlan said. This procedure destroys part of the ovary, and for reasons that are not known, it can trigger ovulation cycles in women who have not been able to become pregnant after taking medication to help induce ovulation.

The woman in this case did not have this surgery, but the case report authors said they suspect the gemcitabine had the same effect, and was likely responsible for her resumed ovulation and subsequent pregnancies. [7 Bizarre Drug Side Effects]

"It's possible that the drug changed the hormonal ratios, allowing for the return of ovulation," Carlan said.

The woman went on to have a healthy pregnancy and had a healthy baby by vaginal delivery at 38 weeks.

Originally published on Live Science.

Single-celled algae known as diatoms, long thought to reproduce asexually, were recently found to be friskier than expected.

Researchers discovered that diatoms do engage in sexual reproduction — and are especially likely to do it when in the presence of the compound ammonium, a waste product generated by most animals.

Previously, scientists had observed the complete life cycles in barely a handful of diatom species, and even among well-studied diatoms, sexual reproduction had never been seen, the researchers wrote in the study, published online July 7 in the journal PLOS ONE. [Photos Reveal the Diversity of Diatoms]

However, the study authors found that they could manipulate the diatom Thalassiosira pseudonana into changing its cell structures to be male or female. All they had to do was eliminate one of the factors that the diatom needed to grow — such as light or phosphorous — and then introduce ammonium, and the diatoms would differentiate into male and female cells.

"Our discoveries solve two persistent mysteries that have plagued diatom researchers," study co-author Kimberly Halsey, a microbiologist at Oregon State University, said in a statement.

"Yes, they have sex, and yes, we can make them do it," Hasley said.

Diatoms are protists, a diverse group made up of unicellular organisms whose bodies have cell walls and highly organized interiors, with a nucleus and an array of specialized structures called organelles. There are an estimated 200,000 diatom species in the world, and they can be found wherever there's liquid water.

Though tiny, diatoms play an important if unseen role in Earth's carbon cycle — marine diatoms generate oxygen through photosynthesis — and in cycling silica, which makes up about 25 percent of the planet's crust and which diatoms incorporate into structures in their cell walls.

But very little is known about how most diatoms grow and reproduce. T. pseudonana is one of only two diatom species that has had its genome sequenced, making it a perfect candidate for identifying changes on the genetic level that could be linked to sexual characteristics — and prior studies had even identified genes that were necessary for sexual reproduction, but determined that they were inactive, the scientists reported in the new study.

Ammonium proved to be the missing ingredient. It sparked a cascade of genetic responses that produced egg and sperm structures. But that wasn't all — more than 1,200 genes also started performing differently when ammonium was present, though the effects of those changes are as yet unclear, the study authors wrote. However, pinpointing ammonium as one of the factors that drives diatoms to reproduce sexually will enable scientists to continue to replicate the behavior in order to study it further, according to Halsey.

"Identifying ammonium as a sexuality inducer potentially opens the door to new avenues of research into breeding and genetic modification to control important traits," Halsey said in the statement.

Original article on Live Science.

In the natural world, stealing is a necessary and frequent strategy for survival. Every animal group includes opportunists that snatch others' fresh kills, pilfer nesting materials or swipe prospective mates from distracted rivals.

But only one type of animal uses thievery at the genetic level for reproduction — an all-female lineage of salamanders in the Ambystoma genus, which contains dozens of species and is widespread across North America. These females mate with multiple males from other Ambystoma species and hijack copies of their partners' genomes, researchers discovered about a decade ago.

However, scientists recently found that the salamanders weren't just stealing the males' genomes. They're incorporating genetic material from males across multiple species into their own genetic code and using all of them at the same time — a process that is otherwise unheard of in animals, researchers reported in a new study. [Album: Bizarre Frogs, Lizards and Salamanders]

In most animals, sexual reproduction typically follows a few basic rules: Females produce eggs, a male's sperm fertilizes the egg and the genome of the offspring incorporates one set of chromosomes inherited from the mother and one from the father.

But something peculiar happened around 5 million to 6 million years ago when a pair of Ambystoma salamanders mated — a mutation emerged that produced a lineage of all-female salamanders, which persists to the present day, according to study lead author Maurine Neiman, an associate professor of evolutionary biology at the University of Iowa.

Among all the Ambystoma species, this lineage has defied easy classification. The females can mate successfully with several species of Ambystoma males; they use the males' sperm to fertilize their eggs — or to simply kick-start an egg's development — but they produce only daughters, apparently making offspring that are essentially copied from their own DNA, Neiman told Live Science.    

From there, the story gets even weirder.

"A shifting kaleidoscope genome"

About 10 years ago, scientists discovered that this all-female lineage practices something so rare that they needed a new term to describe it — kleptogenesis, or "gene stealing." The females were looting genomes from male partners in multiple species, and stashing the DNA within their own cells to pass at least some of it along to their daughters, Neiman explained.

"They pick up a genome and they use it maybe for a few generations, and then they drop it again, so there's not really a continuous evolution of genomes — they're just borrowing and dropping, and borrowing and dropping, again and again. They have a shifting kaleidoscope genome that's made up of copies of genomes from other species," Neiman said.

How exactly the salamanders were doing this — and how all those genes were behaving under these highly unusual conditions — remained a mystery, but it was recently brought to light in the new study, according to the lead author Kyle McElroy, a doctoral candidate in the Department of Biology at the University of Iowa.

"Until this paper, there were no attempts to look at gene expression or whole-genome use in these salamanders," McElroy told Live Science.

Brother, can you spare a genome?

Researchers from two labs — one at the University of Iowa and one at Ohio State University — examined a female salamander from the unisex lineage that had three "extra" genome copies, all stolen from three male species that it had mated with. They used a technique called RNA sequencing to look at 3,000 genes in the female, to see which of the genes across all the genomes were being expressed (or activated); 72 percent of the genes provided by all three partners were expressed equally, the study authors reported.

"Most of what's known about gene expression in polyploids [organisms with multiple genome copies] comes from plants — they shut off the extra genome and only one really gets used — the other degrades over time," McElroy explained.

"What's interesting about this species is that these genome combinations aren't fixed — they uptake new ones and drop other ones. This animal has genomes from three different species that are all somehow working and being expressed," he said.

While it is still unclear which traits these genes control and how the salamanders select which portions of the male genomes they keep and which they discard from generation to generation, these fascinating animals serve as an important example of the unexpected paths that evolution can take toward reproductive success, Neiman told Live Science. 

"Biology is always weirder than you can imagine," she added.

The findings were published online April 1 in the journal Genome Biology and Evolution.

Original article on Live Science.

Men can't nurse babies, so why on Earth do they have nipples?

The answer has to do with how humans develop in the womb, said Ian Tattersall, a paleoanthropologist at the American Museum of Natural History in New York City.

"Basically, males and females are all built from the same genetic blueprint," Tattersall told Live Science. "Then, [they] develop in slightly different directions [in utero and] particularly after we hit puberty." 

Related: Men vs. Women: Our Key Physical Differences Explained

During the first several weeks, male and female embryos follow the same blueprint, which includes the development of nipples. However, at about six to seven weeks of gestation, a gene on the Y chromosome induces changes that lead to the development of the testes, the organ that makes and stores sperm and produces testosterone, according to the book "Exploring the Biological Contributions to Human Health: Does Sex Matter?" (National Academies Press, 2001).

After the testes are formed, the male fetus begins producing testosterone at about nine weeks of gestation, changing the genetic activity of cells in the genitals and brain. But by then, those nipples aren't going anywhere.

Human development explains why males have nipples. But why do men keep this vestigial structure? (A vestigial body part does not serve an evolutionary purpose.)

For starters, having nipples isn't detrimental for males. "There's no real metabolic cost to having nipples," Tattersall said.

Furthermore, just because men don't need nipples, it's not exactly an evolutionary priority to get rid of them.

"The fact is that we carry a lot of evolutionary baggage around with us," Tattersall said. "Natural selection is not hovering there all of the time to get rid of things we absolutely don't need."

Additional reporting by Live Science contributor Ben Mauk.

The testicles are the male gonads — the primary male reproductive organs. They have two, very important functions that are very important to the male reproductive system: they produce gametes, or sperm, and they secrete hormones, primarily testosterone. 

Anatomy of the testis

Testicles, or testes, are oval-shaped organs located in the scrotum, just behind the penis and right in front of the anus on male humans. Each testis weighs 0.35 to 0.5 ounces (10 to 15 grams), according to Virtual Medical Centre (VMC). They are typically 2 inches (5 centimeters) long, 1.2 inches (3 cm) wide and 1 inch (2.5 cm) thick. 

The scrotum is a loose sack of skin that protects the testicles and acts as a climate control system. The testes must be at a temperature slightly cooler than the body temperature for normal sperm development. Muscles in the wall of the scrotum allow it to tighten and relax, moving the testicles closer to the body for warmth or farther away to cool them, according to the Cleveland Clinic.

Each testicle consists of a series of small tubes, or tubules, that contain testosterone and sperm-producing cells. Seminiferous tubules house germ cells — the 23 chromosome cells that men replicate to produce sperm — and they are the site of sperm production, or spermatogenesis, according to VMC. These tubules are tightly coiled within the testis, and each testis may contain up to 900 tubules. The tubules are almost 20 inches (50 cm) long, and a typical testis contains up to half a mile (800 meters) of seminiferous tubules.

A fibrous tissue called the tunica covers the tubules. The tunica has three layers: the tunica vasculosa, the inner layer that consists of blood vessels and connective tissue; the tunica albuginea, which encases the testes and connects to the fibers that surround the epididymis, which transports sperm out of the testes and into the penis; and the tunica vaginalis, which contains fluid that reduces friction between the testes and the scrotum. 

Function

Besides sperm, testicles also produce male hormones called androgens. Androgens control how the male reproductive system grows, and the development of "masculine" body features such as beards and a deep voice. They also influence sexual functions. 

Testosterone is the most common form of androgen. It is responsible for the growth of male genitals and sperm production. Testicles in a healthy male can produce about 6 milligrams of testosterone each day, according to VMC. This isn't always the case, though.

"The testis make 200,000 sperm per minute on average," said Dr. Philip Werthman, a urologist and director of the Center for Male Reproductive Medicine and Vasectomy Reversal in Los Angeles, California. However, "as a man gets older and into his 30s, the amount of testosterone the testis produces starts to drop and continues to decline."

Diseases & conditions 

Typically, every male is born with two testicles. They form in the abdomen, and drop into the scrotum during their seventh month of gestation. 

Sometimes, though, the testicles do not drop, and the baby is born with a condition called undescended testicles. This happens for about 2 percent of males, and in 10 percent of those cases, both testicles are not in their proper position, according to the Mayo Clinic. Typically, this is a problem associated with preemies and the testicles often "drop" within a few months. If not, surgery may be required. 

Once testicles have dropped, they may not stay there. Retractile testicle is when a testicle moves into the groin area. Usually, a doctor can move the testicle back into its proper position, but if it is stuck, it is called an ascending testicle or an acquired undescended testicle. In this case, surgery may be needed to move it into proper position and stitch it into place.

A more serious condition of this organ is testicular cancer. It usually occurs in men 15 and 34 years old. In 2017, around 8,850 new cases of testicular cancer will be diagnosed and 410 deaths will be attributed to testicular cancer in the United States, according to the American Cancer Society. Though these numbers seem large, only around about 1 in 263 males get this type of cancer. Testicular cancer can be caused when the germline stem cells don't turn into sperm cells after a long period of time, according to National Geographic.

Promoting testicular health

Poor health can lead to lower sperm and testosterone production. Maintaining a healthy weight is a large part to good testicular health. According to the Centers for Disease Control and Prevention (CDC), the chance of infertility increases by 10 percent for every 20 pounds a man is overweight. Avoiding periodontal disease, STIs, stress, smoking, excessive drinking and a poor diet can also be good for a male's reproductive health. 

Keeping the testicles cool, just below normal body temperature, can also increase sperm count and quality, according to England’s National Health Service. An easy way to keep them cooler is by wearing loose clothing and by taking breaks often when in warm environments. 

Additional resources

• Mayo Clinic: Undescended Testicle Treatment
• Mayo Clinic: Retractile testicle
• National Cancer Institute: Testicular Cancer
• Cleveland Clinic: Disorders of the Testes

A grow-as-required organ

The placenta is a bowl-shaped mass of tissue with branching blood vessels that acts as a life support system for a fetus. It forms in the uterus at a pregnancy's start and grows over approximately 40 weeks of pregnancy. The placenta attaches to the uterine wall at the top or side and connects to the fetus through the umbilical cord, which supplies the fetus with oxygen and nutrients, and carries waste away.

It is the only organ that reproductive-age humans grow entirely from scratch. But there is also much about the placenta that scientists are just discovering, as they clarify the mechanisms through which it nourishes and sustains a fetus in utero, and how it may regulate body functions related to not only pregnancy, but also the lasting health of the mother after birth.

Here are just a few reasons why the placenta is so fascinating.

Predictor of postpartum depression

A hormone released by the placenta is associated with postpartum depression when found in high quantities prenatally, researchers reported in a study presented in May 2013 at the annual meeting of the American Psychiatric Association.

Although the findings did not suggest that the hormone — called placental corticotropin-releasing hormone (pCRH) — was a cause of postpartum depression, they did show that elevated levels of pCRH during pregnancy could serve as an early warning signal that a woman might be at risk for depression after the baby is born, the study authors explained.

Kick-starts labor

What triggers labor? The answer to this long-unsolved mystery might lie in gene expression within the placenta.

Levels of a substance known as a corticotropin-releasing hormone (CRH) increase in the body during pregnancy, incrementally over time. And high levels of CRH are known to be present when labor starts, suggesting that the hormone plays a role in signaling the body that it is ready to give birth.

When CRH is produced in the placenta, it triggers the release of another hormone that stimulates the placenta to produce even more CRH, suggesting that the placenta is a vital part of the biological "clock" that marks the end of pregnancy and the beginning of labor, according to a study published in August 2015 in the journal Science Signaling. 

Defines the bulk of the mammal family tree

Most of the living mammals are placental mammals; the group includes more than 5,100 species. They arose from a common ancestor that emerged soon after nonavian dinosaurs went extinct, about 65 million years ago.

Scientists reconstructed this creature — called a "hypothetical ancestor," because no fossils of it exist — by using a computer program called MorphoBank to generate a roster of traits representing DNA and morphological data from known placental mammals, and then mapping them to a point in the family tree that would have marked their earliest appearance.

The so-called "mother of all placental mammals" is thought to have been an insect-eater about the size of a squirrel, with an elongated skull and a long, furry tail.

Inspires wound-healing technology

Surrounding the placenta is a thin, protective layer known as the amniotic membrane, an intricate scaffold of proteins that carries nutrients and stem cells for fetal development. Scientists are testing the amniotic membrane as a covering for open wounds that are slow to heal, an idea that was first explored in 1910.

Concerns over the possible transmission of blood-borne diseases such as HIV caused research on amniotic membranes to decline in the 1980s and 1990s. But recently, improved sterilization methods reinstated its use for treating diabetic ulcers and as biological dressings in eye surgeries. 

You can eat it (but that doesn't mean you should)

Placentophagia — consuming the placenta after birth — is an established behavior that has been observed among mothers in most placental mammal species, except those that are semiaquatic or fully aquatic, according to a study published in February 1980 in the journal Neuroscience and Biobehavioral Reviews.

And some human societies observe rituals based around preserving and eating the placenta, Mark B. Kristal, a psychology professor at the State University of New York at Buffalo, wrote in the study.

The notion of eating the placenta after childbirth — raw or cooked — or taking pills made from powdered placenta has risen in popularity in recent years, and the practice is rumored to help with breastfeeding difficulties or postpartum depression. Celebrity Kourtney Kardashian publicly championed the "life changing" powers of placenta-eating in a January 2015 post on Instagram.

However, researchers who analyzed 10 scientific studies found that there were no measurable health benefits to human mothers from eating placenta, according to findings published in October 2015 in the journal Archives of Women's Mental Health.

Birds and the bees

Forget what you know about the birds and the bees: Sometimes you just have to take matters into your own hands.

Reproduction typically requires sperm from a male to fertilize a woman's egg, but in some cases, nature has outsmarted the system. To cope with living in captivity, or a lack of suitable mates, evolutionary adaptations have enabled some creatures to have babies without sex. And while that may sound miraculous, it's not as uncommon as you may think. Here are nine incredible tales of virgin births in the animal kingdom.

Zebra shark

In April 2016, three baby zebra sharks were born at the Reef HQ Aquarium in Townsville, Australia. While the birth of baby animals is not altogether unusual at aquariums, these babies were born to a female shark named Leonie who had been living apart from male sharks for several years. In fact, Leonie was separated from her mate in 2012.

So what gives? At the time, biologists said Leonie could be the first shark ever observed to make the switch from sexual to asexual reproduction. The type of asexual reproduction characterized in Leonie's case is known as parthenogenesis, which occurs when embryos develop and mature without fertilization by a male's sperm. Instead, an egg progenitor cell functions as a surrogate sperm to "fertilize" the egg.

In a study published in January 2017 in the journal Scientific Reports, researchers said Leonie's case suggests that parthenogenesis could be an evolutionary adaptation to a lack of suitable mates. [Read the full story about Leonie the shark]

Yellow-bellied water snake

Turns out, there's at least one yellow-bellied water snake that doesn't need a man. In September 2015, a female water snake at the Missouri Department of Conservation's (MDC) Cape Girardeau Conservation Nature Center gave birth to a litter of snakes without any help from a male. At the time, the snake had not been with a male mate in eight years, and it was actually the second year in a row that she had a "virgin birth," according to MDC officials.

The female snake's impressive feat boils down to parthenogenesis, during which babies are produced by females absent of genetic contribution from a male. Scientists have seen this type of reproduction in other snake species, including copperheads, green anacondas and pit vipers.

With parthenogenesis, the normal division of cells typically results in four egg-progenitor cells, but instead of the female's body reabsorbing three egg-progenitor cells (leaving one egg), one of the female cells behaves like sperm and fertilizes the egg. Why does this happen? Essentially, this type of asexual reproduction occurs when there is a lack of suitable mates. It's evolution in action, folks. [Read the full story about the snake's virgin birth]

Komodo dragon

At London's Chester Zoo, a female Komodo dragon named Flora had the world's first documented virgin births of this lizard species in 2006. The reproductive process, called parthenogenesis, occurs when an unfertilized egg develops to maturity. In May 2006, Flora laid 25 eggs, including 11 that were viable. Zookeepers knew something strange was going on, because Flora had never come in contact with a male Komodo dragon while at the Chester Zoo. A paternity test confirmed that all the genetic material in the eggs had come from Flora. [Read the full story about Flora's virgin conception]

Boa constrictor

No boys allowed! In 2010, scientists discovered that boa constrictors can reproduce by virgin birth. Scientists studied a female boa constrictor from an online store that sold captive-bred boas. The female serpent had given birth to litters twice in two years. The baby boas were all female and were the same caramel color as their mother. Genetic tests revealed that the progeny did not carry any genes from any of the males that had come into contact with the female boa, indicating that they were fatherless.

Interestingly, the female boa experienced this type of asexual reproduction in years when males were present.

"Is it possible that the female selectively chose not to utilize the male sperm if breeding occurred?" study co-author Warren Booth, a population and evolutionary geneticist at North Carolina State University at Raleigh told Live Science in 2010. "Is it possible that the males were genetically incompatible with the female? We simply do not know enough about parthenogenesis in boas to speculate." [Read the full story about fatherless reproduction in boas]

Sawfish

Most "virgin births" in vertebrates (animals with a backbone) are seen with captive animals, but in June 2015, scientists published a study in the journal Current Biology describing what was thought to be the first solid evidence of virgin births in vertebrates in the wild. In Florida, smalltooth sawfish were found to reproduce without sex, instead relying on parthenogenesis.

"Vertebrate animals that we always thought were restricted to reproducing via sex in the wild actually have another option that does not involve sex," study co-author Demian Chapman, a marine biologist at Stony Brook University in New York, told Live Science in 2015.

In the study, the researchers said the babies born from virgin births regularly live in the wild. Parthenogenesis may occur in small or dwindling populations when mates are scarce, the scientists found. And though this may seem like good news for the endangered smalltooth sawfish, parthenogenesis alone is not enough to save species from extinction. Still, the researchers said the findings could inspire conservation efforts. [Read the full story about virgin births among sawfish]

Pit viper

In 2011, scientists revealed that deadly pit vipers can also reproduce without sex. Researchers investigated a female copperhead at the North Carolina Aquarium at Fort Fisher. The serpent came into contact with only one male corn snake over the course of five years. Scientists said interbreeding between the two species was unlikely or even impossible. In 2009, the female copperhead gave birth to a litter, and when scientists analyzed DNA from the babies, they found no evidence of genes from a father.

"With the availability of DNA fingerprinting technologies, we are now becoming aware that the process of parthenogenesis is in fact more common than we ever imagined," study author Warren Booth, an evolutionary and population geneticist at North Carolina State University at Raleigh, told Live Science in 2011.

In the study, scientists said parthenogenesis may have evolved in pit vipers to overcome a lack of suitable mates. [Read the full story about virgin births in pit vipers]

Atlantic blacktip shark

Tidbit didn't need a male to have a baby. Scientists discovered that Atlantic blacktip sharks are capable of virgin births, after performing an autopsy on Tidbit and finding that the female shark was pregnant. It was the second reported case of virgin pregnancy in sharks (the first being a hammerhead shark that gave birth to a single pup with no father).

"We have never observed her in reproductive behavior or showing typical signs of having been bred," Beth Firchau, a researcher at the Virginia Aquarium, said in 2008.

Firchau said there were no males in Tidbit's tank for the prior eight years, and scientists used genetic testing to confirm that the shark's unborn pup contained only DNA from its mom. The discovery was described in a study published in October 2008 in the Journal of Fish Biology. [Read the full story about Tidbit's shark pup]

Hammerhead shark

It started with the unexpected birth of a baby hammerhead shark at Nebraska's Henry Doorly Zoo in December 2001. The surprising delivery stunned zookeepers because the shark tank contained only female hammerheads. What's more, none of the female sharks, which were all caught off the coast of Florida as babies, had been exposed to a male shark during their time in captivity, according to zoo officials.

An analysis revealed that the baby hammerhead's DNA only matched up with its mother, indicating there was no father involved when the female shark became pregnant.

"The findings were really surprising because as far as anyone knew, all sharks reproduced only sexually by a male and female mating, requiring the embryo to get DNA from both parents for full development, just like in mammals," study co-author Paulo Prodohl, an evolutionary biologist at Queen's University Belfast in Northern Ireland, said in 2007. [Read the full story about the surprising hammerhead birth]

Cockroach

As it turns out, female American cockroaches are perfectly capable of having babies without a male. These hardy critters can produce eggs by parthenogenesis, in which unfertilized eggs develop to maturity. But while the cockroaches are capable of fatherless reproduction, they do like to synch up their deliveries with other virgin females. A study published in March 2017 in the journal Zoological Letters found that virgin female cockroaches housed together are quicker to have babies than virgin females that live alone. This could be a primitive example of female cooperation, according to the study researchers. [Read the full story about virgin cockroach births]

The female reproductive system is such an intricate network of organs and fluctuating hormone levels that it can seem mysterious, even to women. But now, scientists have replicated the entire female menstrual cycle in a bento-box-like device that can fit into the palm of your hand.

The device represents a huge leap beyond the standard plastic petri dish as a medium for studying human biology and developing new disease treatments, the researchers said. It also marks a critical feat in a broader effort to mimic the entire human body in artificial models, they added.

The device includes 3D models of key organs, including the ovaries, fallopian tubes, uterus, liver, cervix and vagina. The tissues for each organ were made from stem cells, and the organs are contained within wells that are interconnected by channels, mimicking the human circulatory system. When the artificial organs secrete substances such as hormones, these substances are carried to the other organs and tissues of the system, triggering various phases of the reproductive cycle. The unit has been shown to operate just as a woman's reproductive tract would over the course of an entire 28-day menstrual cycle. [Video: Lifelike Model of Women's Menstrual Cycle Made in a Lab]

"We think we can go longer, but what we're reporting is 28 days," said lead researcher Teresa Woodruff,director of the Women's Health Research Institute at Northwestern University Feinberg School of Medicine, in Chicago."What we're mimicking here is the menstrual cycle itself."

Woodruff and her team named the device EVATAR —like "avatar," but female.

"Avatars are representations of actual people," Woodruff told Live Science. "Eve is kind of the mother of all humans; EVATAR is kind of the mother of all microhumans."

EVATAR is the culmination of five years of work by separate teams that were each assigned an organ to create "in a cube."

Scientists at Woodruff's lab, along with researchers at MIT, developed the ovaries. Julie Kim, an associate professor of obstetrics and gynecology at Northwestern, created the uterus. Spiro Getsios, an assistant professor in dermatology and cell and molecular biology at Northwestern, developed the cervix and vagina; and Joanna Burdette, of the University of Illinois at Chicago, developed the fallopian tubes. EVATAR also includes an artificial liver, because that organ metabolizes many drugs that people might take. 

Most of the organs in the unit were developed using induced pluripotent stem cells, which are stem cells that are made from adult skin or blood cells that have been triggered to develop into tissue for a specific organ. [The 7 Biggest Mysteries of the Human Body]

The key advance of EVATAR is that each organ in the unit is connected by an artificial circulatory system.

"This mimics what actually happens in the body," Woodruff said in a statement from Northwestern University.

Potential applications

Woodruff said that EVATAR could improve researchers' understanding of the female body and help to guide the development of much-needed drugs to treat conditions such as fibroids, endometriosis, polycystic ovary syndrome (PCOS) and many cancers. [5 Things Women Should Know About Ovarian Cancer]

Endometriosisaffects an estimated 10 percent women during their reproductive years, according to the National Institutes of Health. PCOS affects between 5 and 10 percent of women, according to the NIH. Currently, there are very few treatments, other than surgery, for women with these conditions.

Hormones play a key role in these conditions, as well as in many cancers. EVATAR will help researchers to factor in the role of hormones when they study reproductive diseases, according to the researchers' paper, published today(March 28) in the journal Nature Communications.

"The systems are tremendous for the study of cancer, which often is studied as isolated cells rather than system-wide cells," Burdette said in the statement. "This is going to change the way we study cancer."

Another area of research that EVATAR could boost is fertility treatment, particularly for women who have had cancer and have undergone radiation and chemotherapy, which can damage a woman's ability to produce viable eggs, Woodruff said. By mimicking the body's ability to produce eggs, the devices could offer new insight into better ways to grow eggs outside the body.

The devices could also prove useful in finding new birth control drugs that could be taken less frequently than the standard daily pill, said Woodruff, who has a grant from the Bill and Melinda Gates Foundation to develop new contraceptive options for women.

EVATAR is part of a broader NIH project that aims to improve the success rate of new drugs. Currently, drugs are tested in labs and in animal models, said Danilo Tagle, an associate director of the NIH project. But 90 percent of the drugs tested this way fail to work in people, he said.

"That's a lot of wasted expense," Tagle said.

So far, the group has overseen the creation of models of a liver on a chip, a heart on a chip, the human brain on a chip and, most recently, the creation of an artificial human gut that tests how certain drugs are processed by the digestive system. [7 Facts Women (And Men) Should Know About the Vagina]

Of the NIH-funded projects to create artificial organs and systems, EVATAR is among the most complex so far, because it incorporates the hormonal changes of a complete 28-day menstrual cycle, Tagle said. Woodruff and others imagine a time when models such as EVATAR will be scaled up to include the entire human body.

"In the long run, we can create an entire personalized system for individuals where artificial organs are derived from a person's own tissue," she said. "In this way, we could provide a personalized source of testing drug toxicity and drug efficacy that we just don't have at this point."

Woodruff's team is now working on a male version of EVATAR, currently dubbed ADATAR, that mimics the male reproductive system.

In medical research, it has been unusual for studies to focus first (if at all) on female models, often due to sexism. But in this case, starting with the female reproductive tract was useful because there are clear markers (such as ovulation and the shedding of the uterine lining) that their team could look for to make sure their unit was functioning, Woodruff explained.

"When you're building a brand-new, engineered system like this, it's critical to have these predicted outcomes as positive controls," she said. In other words, the team could see that organs in the artificial unit were functioning and interacting as the unit displayed the various phases of the menstrual cycle.

Plus, she added, it's about time a female biological model came first.

Original article on Live Science.

Dr. Jill Maura Rabin is co-chief of the Division of Ambulatory Care and Women’s Health Programs for Northwell Health in New Hyde Park, N.Y. Rabin contributed this article to Live Science's Expert Voices: Op-Ed & Insights. 

President Donald Trump's new administration has introduced a dizzying array of dramatic policy changes, leaving many people struggling to comprehend the impact. But it's his threat to repeal the Affordable Care Act (ACA), also called Obamacare, that affects nearly all 67 million U.S. women of reproductive age, according to the Guttmacher Institute, and their partners

Such a repeal would jeopardize access to free, highly effective birth control. Republican, Democrat, woman or man: Everyone is put at risk from a wrongly politicized issue that has no place in reproductive health.

Previously uninsured Americans aren't the only ones who've benefited from the ACA. In addition to providing health care access to about 20 million adults and children, the act also requires most insurance plans to make free birth control available as preventive care. Even private, employer-based plans must do this. With Congressional Republicans recently defeating an amendment to maintain the birth control mandate regardless of the ACA's status, it's widely anticipated that many Americans who now receive birth control at no cost may soon have to pay some or all costs. [7 Surprising Facts About the Pill

Purely from an economic standpoint — with emotional and psychosocial factors also at stake — this notion is objectionable.  Nearly half of all pregnancies nationwide are unintended, but access to birth control is the best prevention. Unplanned pregnancies resulted in about $12.5 billion in government expenditures in 2008, according to the American Congress of Obstetricians and Gynecologists (ACOG), one group urging Congress to keep the ACA

Birth control access also fattens bottom lines in countless other realms, improving opportunities for education and employment and reducing poverty, according to Planned Parenthood.

President Trump's win in November triggered enormously higher interest among women nationwide in intrauterine devices (IUDs) and other long-acting reversible contraceptives (LARCs), such as hormone injections and implants, Planned Parenthood officials reported. Because IUDs can remain in place for many years, tremendously reducing concerns about unexpected birth-control costs, worried women who want to retain control over their reproductive health are rushing to get the devices while ACA coverage is still in place. I've witnessed this phenomenon firsthand in my own practice

Superior to other pregnancy-prevention methods, because they are effective for up to 10 years without daily vigilance, LARCs are often unaffordable, even for families above the poverty level: The cost of the device plus the procedure to insert it can be more than $700. But one research project, the CHOICE Project in the Midwest, showed that 75 percent of women would choose LARCs if financial barriers were removed.

Where I work, in New York, more protections are in place to maintain free birth control access for state residents, despite the national headwinds. Gov. Andrew Cuomo recently made a bid for a state constitutional amendment protecting a woman's right to choose regardless of federal developments. In addition, he has said he will push for all insurance companies to continue covering free contraception for New Yorkers. [Birth Control Quiz: Test Your Contraception Knowledge]

The state's PCAP (Prenatal Care Assistance Programs) and many family planning programs even outpaced the ACA by providing free reproductive care, including LARCs, to eligible women since 2007. We know that programs like these actually save money: Every dollar invested in such publicly funded family planning services in 2010 saved more than $7 in Medicaid expenditures that would otherwise have been needed to pay the medical costs of maternity and infant care, according to ACOG.

As a physician treating many struggling families, I've seen firsthand what happens when contraception isn't covered. Working several jobs just to pay for rent and food, these individuals simply can't afford the extra expense of birth control, and so may opt to go without. But that's simply not acceptable.

We cannot allow our political views to supersede our humanity.

The reproductive health of our mothers, sisters, aunts, cousins and friends should be a fundamental right and not a topic for political debate.

Original article on Live Science.

The age at which women get their first period, along with the number of children they have, may influence when they enter menopause, a new study from Australia finds.

Women in the study who got their first period before age 12 and had no children were five times more likely to experience premature menopause, and twice as likely to experience early menopause, than were women who got their first period at age 12 or later, and who had two or more children. Women are considered to have premature menopause if they stop menstruating before age 40; they're considered to enter early menopause if they stop menstruating between ages 40 and 44.

A woman’s age at her first period and age at menopause are both markers of reproductive health, and while it's not clear what the link between the two may mean for women's overall health, a better understanding of the possible link between them "will provide us with the opportunity to monitor and intervene as early as possible," to prepare women for the possibility of things like ovarian failure or early menopause, said Gita Mishra, the lead author of the paper and an epidemiology professor at The University of Queensland. [Wonder Woman: 10 Interesting Facts About the Female Body]

In the study, the researchers looked at data that was drawn from nine previous observational studies about 51,450 menopausal women in the U.K., Scandinavia, Australia and Japan. The researchers looked at the self-reported age of a woman’s first period as well as how many children she had.

The median age of menopause was 50, the researchers found. Among all women in the study, 2 percent experienced premature menopause and 7.6 percent experienced early menopause. But among the women who got their first period before age 12 and who also had no children, 5.2 percent experienced premature menopause and 9.9 percent experienced early menopause, according to a statement about the study from the European Society of Human Reproduction and Embryology.

When analyzing their data, the researchers adjusted for factors that could influence women's age at menopause, including their education level, marital status, smoking status, body mass index (BMI) and year of birth.

The researchers noted that most women in the study self-reported their age at their first period, however, and it's possible that the participants might have recalled the age incorrectly. In addition, they said that more studies are needed to tease apart the effects of genes and the environment on the age of a woman when she has her first period and her age at menopause. [Conception Misconceptions: 7 Fertility Myths Debunked]

"To improve health outcomes in later life, we need to be thinking of the risk factors through the whole of the woman’s life, from the early years and the time of their first period, through to their childbearing years and the menopausal transition," Mishra told Live Science.

The researchers wrote in their findings that they hope that the study will help shape clinical guidelines for reproductive health. For instance, doctors may decide to prepare women with no children, who had their first period before age 12, for the possibility of early menopause, to help them make informed decisions about their reproductive health.

Originally published on Live Science.

Egg freezing has been touted as a way for women to put off having children, giving them more time to  work on their careers or search for the right partner. But a new study finds that few women who freeze their eggs actually end up using them.

In the study, researchers in Australia surveyed nearly 100 women who had elected to freeze their eggs, between 1999 and 2014, as a way to delay childbearing. (None of the women in the study had a medical reason for freezing their eggs.)

On average, the women were 37 years old at the time they froze their eggs, and 40 years old at the time they completed the survey. The majority of women (86 percent) were single when they froze their eggs, and most (67 percent) were single at the time they completed the survey.

Overall, just 6 percent of the women had used their frozen eggs at the time of the survey, and 3 percent had given birth using the frozen eggs. [5 Myths About Fertility Treatments]

About 1 in 5 of the women (22 percent) had been pregnant at some point since freezing their eggs. In most of these cases, the women had conceived naturally, or had undergone in vitro fertilization using "fresh" eggs (rather than their frozen eggs), and some of the women had had miscarriages.

When asked why they hadn't yet used their frozen eggs, most of the women said that they didn't want to be a single parent, or that they wanted to try to conceive naturally.

And when asked if they still planned to use their frozen eggs, nearly 70 percent said it would depend on their circumstances, while just 21 percent said they were definitely planning to use their eggs.

The researchers concluded that information on the proportion of women who return to use their stored eggs, as well as information about their reasons for not using the eggs and their overall pregnancy outcomes, "might help women to make more informed decisions about whether to freeze oocytes," they wrote in the Jan. 6 issue of the journal Human Reproduction.

Previous studies have had similar findings. For example, researchers at one fertility clinic in Santa Monica, California, found that, from 2007 to 2012, 232 women froze their eggs at the clinic to delay childbearing, but 95 percent of these women still had not used their eggs by 2015. [5 Surprising Facts About Egg Freezing]

It's important to note that many women in the new study had only recently frozen their eggs — nearly half  the women said they had frozen their eggs within the last two years, and this may, in part, explain why so few women reported using their eggs, the researchers said.

In addition, the researchers noted that 6 percent of women in the study who ended up using their eggs had all used an older method for egg freezing, known as "slow freezing," and only half of these women who tried to use the eggs frozen by this method ended up having a baby with their frozen eggs. But the women who froze their eggs in more recent years (after 2012) used a newer technology for egg freezing, called vitrification. And although it's too soon to tell, it's possible that the women who used this method will have a greater chance of having a baby using their frozen eggs, the researchers said.

Still, "these results demonstrate the diverse potential reproductive outcomes and reproductive heterogeneity of women who freeze oocytes for nonmedical reasons," they said.

When using frozen eggs, the chances of pregnancy depend, in part, on how old women are when they froze their eggs, and the number of eggs they chose to freeze.

A 2016 study found that the chances of having at least one baby from eight frozen eggs was 41 percent in women who are younger than 35 when they freeze their eggs, and 20 percent in women who are 35 or older when they freeze their eggs.

The new study was funded by Melbourne IVF, the fertility clinic where participants went to freeze their eggs.

Original article on Live Science.

Sure, she used to have a mate at the Reef HQ Aquarium in Townsville, Australia. The pair even had several litters before they were separated in 2012.

But Leonie had been living apart from males for the past few years, so her keepers were surprised when she laid eggs that produced three baby sharks in April 2016. Leonie could be the first shark ever observed to make the switch from sexual to asexual reproduction.

"We thought she could be storing sperm; but when we tested the pups and the possible parent sharks using DNA fingerprinting, we found they only had cells from Leonie," said University of Queensland biologist Christine Dudgeon, who described the case in the journal Scientific Reports Monday (Jan. 16). [7 Unanswered Questions About Sharks]

Leonie's case marks the first time scientists have seen this type of asexual reproduction —known as parthenogenesis—in the zebra shark (Stegostoma fasciatum).

Parthenogenesis occurs when embryos develop and mature without fertilization by a male's sperm. Rather, an egg progenitor cell that usually gets absorbed by the female's body acts as a surrogate sperm to "fertilize" her egg. This reproduction strategy is more common in plants and invertebrate organisms. However, scientists have been documenting an increasing number of vertebrate species that can have virgin births even when their species normally reproduces sexually. For example, Komodo dragons, the world's largest lizards, have given birth by parthenogenesis. So have wild pit vipers, blacktip sharks, chickens and turkeys.

In most of these previous parthenogenesis cases, the females were from captive environments and never had any exposure to male mates during their reproductive prime, Dudgeon and her colleagues wrote. That makes Leonie one of the rare individuals known to have had babies by sexual reproduction only to switch to asexual reproduction later on. (Scientists have reported similar cases in a boa constrictor and an eagle ray.)

"Leonie adapted to her circumstances, and we believe she switched because she lost her mate," Dudgeon said in a statement. "What we want to know now is, 'Could this occur in the wild?' and, if so, 'How often does it?' One reason why we haven't seen it before could be because we haven't been looking for it. It might be happening in the wild, but it's never been recorded in this species before."

If parthenogenesis is indeed an evolutionary adaptation to a lack of suitable mates, that could have implications for the survival of zebra sharks. The species, which is found in the western Pacific and Indian oceans, is listed as endangered on the International Union for Conservation of Nature's (IUCN) Red List of Threatened Species.

Dudgeon plans to monitor Leonie's pups to find out if these asexually produced sharks can have pups of their own with a male partner.

"You lose genetic diversity with generations of asexual reproduction, so we'll be seeing if these offspring can mate sexually themselves," Dudgeon said.

Original article on Live Science.

In the not-too-distant future, scientists may be able to create human sperm and egg cells in a lab dish. That possibility brings hope for treating infertility, but also poses significant ethical dilemmas — from "embryo farming" to designer babies, some researchers argue.

In a new paper, researchers at Harvard and Brown universities discuss the theoretical implications of creating sperm and egg cells in a lab dish, referred to as "in vitro gametogenesis," or IVG. It's currently feasible to perform IVG in mice, as has been shown in several remarkable experiments that were published in recent years, said the paper's authors, Dr. Eli Adashi, a professor of medical science at Brown University in Providence, Rhode Island; I. Glenn Cohen, a professor at Harvard Law School in Boston; and Dr. George Daley, dean of Harvard Medical School also in Boston.

IVG is not yet possible in humans — just from a scientific standpoint, many technical barriers remain before human gametes could be made from other human cells, the authors said. Even so, the technology could arrive sooner than we think, and so it may be wise to ponder some of the regulatory and ethical questions raised by IVG now, they said. [Conception Misconceptions: 7 Fertility Myths Debunked]

"With science and medicine hurtling forward at breakneck speed, the rapid transformation of reproductive and regenerative medicine may surprise us," the authors wrote in their paper, which was published today (Jan. 11) in the journal Science Translational Medicine. "Before the inevitable, society will be well advised to strike and maintain a vigorous public conversation on the ethical challenges of IVG."

What is IVG?

IVG is the generation of sperm and egg cells in a lab dish from pluripotent stem cells, or cells that are capable of becoming any cell type in the body, the paper said. These could be embryonic stem cells, which are found in embryos during early stages of development, or so-called induced pluripotent stem cells (iPS cells), which are "adult" cells (such as skin cells) that have been reprogrammed so they are once again capable of becoming any cell type. Hypothetically, IVG could create human sperm and egg cells from adult skin cells.

Scientists have recently reported key successes with IVG in mice. In 2016, scientists in Japan reported that they could recreate the entire cycle of mouse egg production in a lab dish. They started with either embryonic stem cells or iPS cells from mice, and reprogrammed them into so-called primordial germ cells, which are the precursors of sperm or egg cells. Then, they mixed these cells with other cells that support the development of mouse eggs, creating a sort of ovary in a dish. They added various hormones and other compounds to the dish, and eventually found a way to coax the cells into developing properly to become egg cells. These egg cells were fertilized with sperm, and resulted in healthy baby mice pups.

Also in 2016, researchers in China said that they had created sperm-like cells from embryonic stem cells that were taken from mice. For these experiments, the researchers first turned embryonic stem cells into primordial germ cells and then cultured these cells with testosterone and other hormones, which prompted the cells to develop into immature sperm cells.

Other studies suggest that similar feats with human cells might be possible. In 2009, researchers at Stanford University reported that they had transformed human embryonic stem cells into germ cells, which could theoretically give rise to sperm and eggs (although the researchers did not let the cells develop for long enough to become sperm or eggs).

"These findings suggest that experimental refinements likely will permit derivation of functional eggs and sperm from [human stem cells] in the not too distant future," Adashi, Cohen and Daley wrote in their paper.

IVG in people

In people, IVG could revolutionize the way that doctors perform in vitro fertilization (IVF) to treat infertility, Adashi, Cohen and Daley said. Currently, women who have fertility problems may undergo IVF, which involves several weeks of hormone injections to stimulate the production of eggs, and then a procedure to retrieve the eggs, which is done at a doctor's office. IVG would eliminate the need for these steps and would also eliminate the need to find an egg donor if a woman couldn't use her own eggs, they said.

What's more, with an abundant source of egg and sperm cells, researchers could more easily study the process of embryonic development and certain diseases, they said.

But IVG could also lead to new ethical problems. For example, clinics might create scores of eggs or embryos for their clients. "IVG may raise the specter of 'embryo farming' on a scale currently unimagined, which might exacerbate concerns about the devaluation of human life," they said.

In addition, couples might create a large number of embryos in order to choose the best traits for their child. (Currently, IVF usually generates just a handful of embryos, which doctors can screened for certain diseases before choosing which ones to implant..) "IVG could, depending on its ultimate financial cost, greatly increase the number of embryos from which to select, thus exacerbating concerns about parents selecting for their 'ideal' future child," they said.

IVG might even one day allow people to create "single-parent babies," in which cells from one person are used to produce both sperm and egg. However, it's not yet clear whether cells from a male can produce eggs (and vice versa), or whether a baby with just a single parent would have the same health problems that can arise from having closely related parents, they said. [Controversial Human Embryo Editing: 5 Things to Know]

Finally, it might also be possible for people to become parents without their knowledge, if sperm and egg cells could be created from shed skin cells, they said.

Still, in the near future, the biggest impact of IVG will likely be to enhance the scientific understanding of reproductive cells, the researchers said. Any applications of it could be much further out.

The authors note that some of the concerning scenarios raised in their paper  would require a deeper understanding of human genetics than we currently have in order to be made possible. "Nevertheless, even at this stage, it is worth contemplating the ethical issues raised by such a possible future," they said.

Original article on Live Science.

Forget about the stork — it's the albatross that should be in charge of baby delivery. That's because the world's oldest wild breeding bird mother, a 66-year-old albatross named Wisdom, is incubating another egg, likely her 41st one, experts say.

Wisdom's new chick is unexpected; many albatrosses don't breed for two consecutive years, and Wisdom had a chick last year. Rather, most lay an egg one year and then take a break the next, instead investing their time and energy into molting their feathers, said researchers at the Midway Atoll National Wildlife Refuge and Battle of Midway National Memorial, located about 1,400 miles (2,250 kilometers) northwest of Hawaii.

Having healthy feathers is important because albatrosses spend almost 90 percent of their time flying, often covering thousands of miles as they search for food in the north Pacific Ocean, the researchers said. [Adorable Photos of Baby Shorebirds]

For whatever reason, Wisdom chose to lay an egg this year. The last time researchers saw the famous mom, she was sitting on her egg, waiting for the return of her mate, Akeakamai (a Hawaiian word that means "a love of wisdom, scholar"). Albatrosses often tag-team, with one parent incubating the egg while the other goes out to sea to hunt for food.

Every year, the duo returns to the wildlife refuge at Midway Atoll, an albatross hotspot.

Kristina McOmber, the refuge's biology program volunteer crew leader, discovered the expecting bird on Dec. 3. McOmber spotted Wisdom thanks to the bird's bright-red leg band placed there by scientists. Akeakamai was seen by the nest on Nov. 23, refuge volunteers said.

"I find it impressive that not only has Wisdom returned for over six decades as the oldest living, breeding bird in the wild, but also that biologists here on Midway have been keeping records that have allowed us to keep track of her over the years," Charlie Pelizza, the U.S. Fish and Wildlife Service's acting project leader for Midway Atoll Refuge and Memorial, said in a statement. "The staff was abuzz with the news that Wisdom was back and incubating. It's amazing what a bit of good news can do to brighten the day."

Biologist Chandler Robbins first banded Wisdom in 1956. Robbins, who is now 98, has kept abreast of Wisdom's travels over the years — an estimated 3 million miles (5 million km) in her lifetime — and heralded in the nine chicks she's laid since 2006, including Kūkini, who hatched in February 2016.

Wisdom may be a celebrity, but she's not a prima donna. Instead, she shares the National Wildlife Refuge with about 70 percent of the world's Laysan albatross (Phoebastria immutabilis) population, and almost 40 percent of the world's black-footed albatrosses (Phoebastria nigripes). The short-tailed albatross (Phoebastria albatrus), which the International Union for Conservation of Nature classifies as a vulnerable species, also occasionally nests on the Sand and Eastern islands within the refuge.

The birds typically arrive at the refuge in late October, and they number in the hundreds of thousands by the end of November, the biologists said.

Original article on Live Science.

It's generally thought that women are born with a finite number of egg cells, and cannot grow new ones. But in a new study, researchers got a surprise when they found that women undergoing a particular chemotherapy had a much greater number of eggs in their ovaries than expected.

The reason for the finding isn't clear, but it suggests that the chemotherapy may spur the development of new eggs, the researchers say.

If confirmed, it would be the first time that scientists have seen new egg cells formed in adult women. And understanding exactly how this happens could aid in the development of fertility treatments that allow women to produce more eggs, the researchers said.

However, the researchers caution that the study was small, and the findings do not prove that the chemotherapy treatment caused the production of new eggs. In addition, it's not clear whether the greater number of eggs seen in these women after the chemotherapy treatment would help with their fertility. In fact, another part of the study found that the eggs from these women didn't grow as well in a lab dish, compared to eggs from healthy women. [Conception Misconceptions: 7 Fertility Myths Debunked]

"This study involves only a few patients, but its findings were consistent and its outcome may be significant and far-reaching," study researcher Evelyn Telfer, a professor at the University of Edinburgh's School of Biological Sciences, said in a statement. "We need to know more about how this drug combination acts on the ovaries, and the implications of this."

New eggs?

Women are born with all of the eggs they will use in their lifetimes, but the eggs need to mature inside structures called follicles. Typically, one follicle matures each month, and releases an egg. As women age, the number of follicles in their ovaries declines, which reduces their chances of pregnancy.

Some cancer treatments accelerate the loss of follicles, and thus hurt a women's fertility. But other cancer treatments don't seem to have an effect on fertility.

In the new study, the researchers originally set out to examine why a common chemotherapy treatment for Hodgkin’s lymphoma (a cancer of white blood cells) doesn't appear to affect fertility. The treatment is a combination of four chemotherapy drugs — adriamycin, bleomycin, vinblastine and dacarbazine — or ABVD for short.

The researchers analyzed samples of ovarian tissue donated by 8 women who had undergone ABVD, 3 women who had undergone a different type of chemotherapy and 12 healthy women around the same age.

Women who received the ABVD treatment had a much greater number of immature follicles in their ovaries —up to 10 times higher in some cases — than healthy women and those who'd received the other chemotherapy, the study found. Women who'd received ABVD also had a much greater number of follicles than would be expected based on their age.

The follicles in ABVD group also appeared younger — similar to those seen in girls before they go through puberty.

When the researchers tried to grow the follicle in a lab dish, those from the ABVD group didn't grow as well as those from the other two groups - only about 20 percent of follicles from the ABVD group showed growth, compared to 42 to 46 percent in the other two groups, the study found. This limited follicle development is also comparable to what's seen in prepubescent girls, the researchers said.

Future research

The researchers speculate that the ABVD treatment may active stem cells within the ovary to produce new eggs.

"It could be that the harshness of the treatment triggers some kind of shock effect or perturbation which stimulates the stem cells into producing new eggs," Telfer told the Telegraph.

But there could be other explanations, including that the egg follicles were damaged during treatment and split into two or more parts, David Albertini, laboratory director at the Center for Human Reproduction in New York, told the Guardian.

Future studies will examine the effect of each of the four chemotherapy drugs separately, to better understand the mechanism that may be leading to an increased number of follicles, the researchers said.

The study was published online Dec. 5 in the journal Human Reproduction.

Original article on Live Science.

Women who have their last baby when they are older than age 35 may have sharper cognitive skills later in life than those who finished with their pregnancies at a younger age, a new study suggests. Researchers found that the women in the study who had their last baby when they were older than 35 were better at memorizing lists of words at age 60, compared with those who stopped bearing children earlier on.

"The study provides strong evidence that there is a positive association between later age at last pregnancy and late-life cognition," lead study author Dr. Roksana Karim, an assistant professor of clinical preventive medicine at the University of Southern California, said in a statement. She noted, however, that the researchers would also not necessarily recommend that women wait until after the age of 35 to finish having children, because of the general increase in health risks that occurs when women become pregnant in their late 30s.

In the study, the researchers looked at 830 post-menopausal women whose average age was 60. Previous research has suggested that many women experience declines in cognitive skills after menopause, and the researchers wanted to see whether the timing of the women's reproductive history could affect this decline. [Conception Misconceptions: 7 Fertility Myths Debunked]

The researchers gave the women a series of tests that examined the participants' cognitive skills, including their executive function — which involves planning and focusing — and their memory. For example, they tested how well the women could remember lists of words or retell a story after being distracted.

The researchers also looked at the women's reproductive history, including how old they were when they got their first period, as well as whether the women had ever used birth control pills and whether they had ever been pregnant.

The researchers found links between the timing of some of those events and the women's cognitive skills. For example, they found that women who got their first menstrual period before turning 13 tended to have better executive function than those who got their first menstrual period when they were 13 or older, according to the study. [6 Fun Ways to Sharpen Your Memory]

The women who had used birth control pills for at least 10 years were also better at memorizing lists of words and had better critical-thinking skills than those who had never used those pills or who had used them for less than 10 years, according to the study.

Moreover, among women who had ever been pregnant, those who had been pregnant at least twice had better overall cognitive ability than those who had only been pregnant once. In addition, those women who had their last child at age 35 or later had a better memory for lists of words than those who had their last child before they reached the age of 35.

It is not completely clear why these factors may be linked to better cognition later in life, the researchers said. But the link likely has something to do with exposure to high levels of the female hormone estrogen that accompanies these events, they said.

For example, girls who start their period early in life are exposed to estrogen early in life, which may be beneficial to the development of their brains, the researchers said. The researchers think that this is a likely theory because some animal research has suggested that estrogen may have positive effects for brain chemistry and structure, Karim told Live Science.

Further research should continue to examine this association in humans, the researchers said.

Originally published on Live Science.

Starting with skin cells rather than egg cells, Japanese researchers say they have generated eggs that led to healthy mouse pups capable of living normal lives and reproducing.

Mammals, of course, have always reproduced via the sperm of one animal combining with the egg cell of another. But the new research started instead with a skin cell from a mouse's tail and transformed it into egg cells, then matured those eggs in a laboratory dish and finally fertilized them and implanted them into a female mouse.

Although only 1 percent of the cells led to live births, the animals that were born alive were healthy, fertile, and lived a normal lifespan, says Katsuhiko Hayashi, a stem cell biologist at Kyushu University in Fukuoka, Japan, and the senior author of a paper on the research, published Monday in Nature.

Although this process likely remains decades away from a stage at which it could work in people, the research suggests it may someday be possible for women who lack eggs, or for men without sperm, to get replacement cells made from their own skin. If that becomes possible it could extend the age of human fertility by decades, help preserve endangered animal species and someday perhaps allow same-sex couples to have their own genetic children.

In the meantime, several experts say they are highly impressed by the new study. "This is quite an amazing piece of research," says Azim Surani at the Gurdon Institute in Cambridge, UK. He was not involved in the latest work, but he supervised Hayashi's postdoctoral fellowship there. "People might have thought this was science fiction, but it does work," Surani adds.

In an earlier study published in Cell, Hayashi and his colleagues had shown that they could generate healthy mouse pups by maturing skin-cell-derived eggs inside the mouse mother. In the new work the maturation took place entirely in a lab dish, making it much closer to a process that could one day be used in people. "That's quite a remarkable feat, actually," Surani says.

Shinya Yamanaka won a 2012 Nobel Prize for his 2006 work transforming skin cells into stem cells that are theoretically capable of becoming any cells in the body. But Hayashi is one of just a few scientists worldwide trying to make germline cells from these so-called induced pluripotent stem (or iPS) cells.

To transform a stem cell into a primordial egg cell, the researchers had to design an environment that recapitulated cell signaling and promoted development through several stages, says Shoukhrat Mitalipov, a reproductive and developmental biologist at Oregon Health & Science University, who was not involved in the study. "This is a tremendous amount of work. I have to congratulate the team. It's such a huge accomplishment," Mitalipov says.

Hayashi says his next step will be to try to repeat this process in a non-human primate, which will be much more complicated. To help mature the mouse egg cells he simply took supporting cells from the mother's ovaries. In a primate he will first need to generate these supportive cells from stem cells—something that has never been done before.

Hayashi says the mouse research has taken him four years, and he expects it would take at least twice that long to achieve the same results in people. It is far too early to try that, he says.

"At the moment I must say that this kind of system should not be used for the human, because there are big risks," he warns, adding that the process might lead to abnormal or seriously ill offspring. It may be possible to eventually make it safer by using a combination of technical improvements and advances in genetic analyses of embryos, he says. In a mouse it is ethically allowable to examine a large number of the embryos generated by research, and to accept the possibility—though not yet seen—that the pups might have genetic defects. Similar studies would not be possible in human research.

"In mice we can also work directly on the organism itself. We can look at events in vivo, introduce mutations and see what happens," Surani says. "In humans we need a culture system to study the germ line, because we can't do the kinds of experiments we can do in mice."

Surani admits there will be challenges to getting this type of reproduction to work in people, and suspects the process could take a long time—possibly one to two decades. But Hayashi's achievements so far make him confident of eventual success. "Sometimes when you know something is possible, it takes off the mental barriers you might have. You start being more optimistic," he explains. "I wouldn't say it's impossible. I think it is possible."

This article was first published at ScientificAmerican.com. © ScientificAmerican.com. All rights reserved. 

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For some species of spiders, mating comes with a deadly risk — the possibility of being eaten by their much larger female partner. But in two species of widow spiders — the venomous spider group that includes black widows — males deploy an ingenious strategy to avoid being cannibalized during sex, according to a new study.

Scientists recently discovered that widow spider males Latrodectus hasselti and Latrodectus geometricus prefer to mate with females that are not yet sexually mature but which still have internal structures that are capable of storing sperm, which the males access by piercing the female's exoskeleton.

This sexual sneak attack is a win-win situation for the male. He literally plants the seeds to successfully fertilize the female at a later date, and is able to scuttle away from the encounter with his dignity — and his head — intact. [In Photos: The Amazing Arachnids of the World]

Sexual cannibalism is common in widow spiders, but males mating with immature females to avoid being cannibalized is behavior that was previously unheard of, the researchers wrote in a new study.

Study co-author Maydianne C. B. Andrade, a professor in the Department of Biological Sciences at the University of Toronto, Scarborough, has studied widow spiders for nearly two decades, but had never observed this behavior until recently. She told Live Science in an email that it was first brought to her attention by a member of her research team — M. Daniella Biaggio, the study's lead author.


Biaggio reported that not only were the males mounting immature females, but they were also difficult to separate from their partners.

Once the scientists realized that the spiders were mating, they isolated the females and later found that their eggs had been successfully fertilized, noting in the study that the females molted normally and subsequently produced offspring, even though they had not mated as adults.

Andrade explained that after she presented her preliminary findings at a conference, she was approached by another scientist, Yael Lubin from Ben-Gurion University of the Negev, whose doctoral students Iara Sandomirsky and Ally R. Harari had observed similar behavior in widow spiders. The researchers decided to combine their efforts in a new study investigating the activity that had been hiding in plain sight.

"Dani Biaggio and Iara Sandomirsky discovered the behaviors," Andrade said. "They brought 'new eyes' to the system."

This mating strategy is challenging for males — the window of opportunity for finding a female that has recently developed her sperm-storing receptacles but is not yet sexually mature is small, Andrade explained. And there is still much to be learned: How the males even find the immature females, which don't produce the signature "come hither" pheromones that mature females emit; what the physical cost is to females that are fertilized before they're sexually mature; and how widespread this behavior is — not just in widows, but in other sexually cannibalistic spider species as well.

"The focus in widow research has largely been on cannibalism and related phenomena; very few field studies include a systematic examination of behavior throughout the lifespan," Andrade said in an email. "I suspect this will change," she added.

The findings were published online Sept. 21 in the journal Biology Letters.

Original article on Live Science.

Detachable penises. Genital plugs. Sexual cannibalism.

Dating and mating in the animal kingdom aren't just complicated — they can be fraught with violence and danger. Even so, they're the only game in town. Every species must reproduce, and there are many paths to successful reproduction, though those paths may sometimes be as convoluted as the corkscrew genitals of a mallard duck.

The prospect of exploring mating positions in frogs, porcupines' use of sex toys or hermaphroditic sea slugs' penis spines might seem daunting to some, but not so for biologist and writer Carin Bondar. She leads the way into the intriguing world of animal sexual practices in her new book, "Wild Sex: The Science Behind Mating in the Animal Kingdom" (Pegasus Books, 2016). [Top 10 Swingers of the Animal Kingdom]

From finding a mate, to procreating, to dealing with the successful outcome of mating — offspring — "Wild Sex" investigates the often-harsh realities of sexual behaviors practiced by animals large and small.

Bondar is the current lead presenter for Discovery World's "Brave New World with Stephen Hawking" and host of the web series "Wild Sex" for Earth Touch News Network. She has appeared on Discovery Channel's "Outrageous Acts of Science" and has hosted online and television programs created by National Geographic Wild, Scientific American and the Science Channel.

Recently, Bondar spoke with Live Science about the unusual sexual behaviors and equipment used by humans' closest relatives and most distant cousins on the tree of life, and what people's interest in animal sex reveals about them. [Live Science Book Giveaway: 'Wild Sex' by Carin Bondar]

(This Q&A has been edited for length and clarity.) Live Science: What was it about sex in the animal kingdom that first attracted your attention as a biologist?

Bondar: Ironically, it happened when I was at home enjoying the young products of my own sexual activity — my children. I started blogging, and though I didn't just focus on sexual topics, I noticed engagement was so much higher when the topic was sex — and the crazier, the better! So I rolled with it and went more in that direction. And then I got a call from Earth Touch [News Network] to write and host a series about animal sex, and six weeks later, I was on a plane to South Africa. It just swept me up in its own tidal wave.

LS: For many people, sex is primarily about pleasure. How much is pleasure a factor for animals?

Bondar: Very, very little! Unfortunately, there's a massive dichotomy between sexual cells of males and females, so males have incredibly abundant sperm, and females have very rare and expensive eggs. Generally speaking, males always want to have more sex and get as many partners as they can, and females want to be protective of their expensive treasures and choose carefully who gets to fertilize them.

From bugs to mammals and everything in between, this sets the scene for violence, conflict and war. There's no champagne, no roses. It's very much, "I've evolved these structures to torture you and hold you down so I can have sex with you."

LS: What are some of the risks that animals in certain species face during sex?

Bondar: Bedbugs and some of the nudibranch species use what is aptly termed traumatic insemination, because it literally is a stab wound to the female's body. The sperm will travel from these wounds into her ovaries, so she basically ends up with stab wounds all over her body that can get infected, which could certainly affect her well-being and general health. [Animal Sex: 7 Tales of Naughty Acts in the Wild]

Some canine species have penis bones that get massively inflated during sex, so they can't separate. That's actually an evolutionarily smart thing to do, to not let your female get away until you get sperm in there, and it's also a fail-safe for the male, who can't get out until he finishes the job. But it comes with a huge element of danger from predators.

Then, there are a lot of invertebrates that are hermaphroditic, male and female at the same time. Sometimes they can fertilize themselves, but often they need an actual partner. Taking the male role is more favorable because it's less work, so these sexual encounters tend to become extremely violent.

LS: What about spider and insect species where males are cannibalized by females during sex? That seems like even when a male succeeds at reproducing, he loses.

It seems horrific to us, but it's reproductively clever — these males can actually increase their reproductive success by dying!If the female is busy feasting on his body, she's not out getting more sperm, so his sperm can dominate.

In mammals where sperm is so plentiful, it's a vastly different story than in spider species, where males only have one or possibly two chances to copulate in their entire lives. [101 Animal Shots You'll Go Wild Over]

We see the same thing in those infamous preying mantis videos where the female rips the male's head off — his genitals are still doing the deed while she's busy eating his head and body. His sperm has lots of time to travel where it needs to go, and she's not seeking new sperm. That's kind of a tough one for us to swallow (so to speak), but it is a reproductively sound strategy.

LS: Many species appear to engage in a type of "arms race" when it comes to sex, with female behavior or biology thwarting male advances, and male strategies and anatomy trying to work around that. But don't they want the same thing — to procreate?

Bondar: They do. However, they want it on their own terms.

These arms races are ridiculous. Like in the water strider, males have evolved these crazy structures that fit around eyeballs of the females to keep them in place, and the females have these anti-grasping spring things that they can use to spring males off when they're trying to have sex with them.

We assume as biologists that animals ultimately want to maximize biological fitness, in terms of getting their genetics to the next generation. But the problem is that females don't want just any sperm. They want the best sperm. Males, on the other hand, because it's so easy for them, they can afford a few missteps.

If I'm a male, and I put my sperm out there as often as I possibly can and with whomever, some will be bad mothers or bad children. But I'll do better in the long run. For females, it's a completely different story.

Think of the human case. If I get fertilized, I'm out of reproductive commission for at least another nine months or more, as I then breast-feed, so that takes me out of the reproductive game for close to a year. If I let any man fertilize me willy-nilly (pun very much intended), I'm jeopardizing my own biological fitness, because that's a huge commitment for me. I'm doing this huge thing in my body for the embryo.

LS: I was going to ask for the most extreme example of a sexual behavior, but … there are so many. Is there one in particular that stood out to you when you were researching this book?

Bondar: There's one of those hermaphrodites I was talking about, a sea slug. As many hermaphrodites do, each one is trying to be the male. What this species in particular does is it takes its razor-sharp penis and stabs the partner directly in the forehead. And they're doing this with a degree of accuracy and precision that's unprecedented.

Biologists puzzled about this for long time, until scientists looked at the chemical makeup of what was getting deposited. And they found that there was some kind of neurochemical warfare going on. They were ejaculating into the cerebral ganglia of the receiving partner, so they manipulated the partner to become more female. Since being female is more expensive, it makes sense for them to want to be the male as much as possible.

The other one that I really like is a cannibalistic spider species. Like many other species, they have something called a mating plug, something that plugs up the female's genitals after she's been fertilized. Sometimes males put them in, and sometimes females seal themselves up.

In this species, females take the substance they'd use to seal themselves up, and they use it to ensnare males because they're hungry. They make their genitals into a spider-sized sticky trap. A male comes along, and she'll trap him. He'll die there, and she won't necessarily eat him right way. So she'll be walking around with a dead guy on her genitals until such time as she decides to eat him.

LS: What might all these examples of different animal sex practices mean for readers in terms of understanding their own sexual behavior?

Bondar: The breakdown of the book — trying to find a mate, trying to have sex with your mate and then dealing with the aftermath of the sex — that affects us just like it does every other animal.

It's funny and gruesome and horrible to talk about all these "insert part A into slot B" examples, and people like to hear about that. But the reason people are so interested in sex in other animals is [because] we're so obsessed with it in our own lives. I always like to bring it back to humans remembering that we're part of the animal kingdom, even though we often pretend that we're not.

"Wild Sex: The Science Behind Mating in the Animal Kingdom" was published Aug. 6.

Original article on Live Science.

Male snakes in the viper family — a venomous group of snakes that have hinged fangs — are known for engaging in fierce wrestling matches when they compete for females. But combat between two different viper species has never been observed — until now.

On Sept. 6, Dawn Kelly was astounded to come across an unexpected and intense battle between a cottonmouth and a copperhead near her cabin in Snowball, Arkansas, close to the Buffalo National River Park in the northern part of the state.

Kelly captured video footage of the unusual encounter on her smartphone, and shared it with biologist David Steen, an assistant research professor at Auburn University Museum of Natural History in Alabama. Steen is an active science communicator on Twitter (@AlongsideWild) and on his blog, Living Alongside Wildlife. He is particularly well-known for answering questions from the public about snakes. [101 Animal Photographs You'll Go Wild Over]

In the video, two sizable males square off in a rural area next to pieces of discarded tin, wrapping their bodies around each other in a test of strength so intense that Kelly was able to film for several minutes without disturbing the serpents, she said.

Kelly told Live Science that she was in her cabin when she looked out the window and noticed that her neighbor's dog was motioning toward two snakes in the weeds. She went outside to take a closer look, and that's when she saw that not only were the snakes battling each other, but also that they were two different viper species.

Having grown up on a farm, Kelly said she was no stranger to Arkansas wildlife. She once nursed an injured king snake back to health, and described herself as "the girl who flips over every piece of plywood to see who's under it." Kelly said she was familiar with snakes in the area. Vipers like cottonmouths and copperheads are common, though they tend to be reclusive and are not seen as frequently as other types of snakes, she added. She said she recognized that what she was seeing was highly unusual, and so she started filming it with her phone.

Kelly described the vipers as "well over 2 feet [0.6 meters] long," and they were so preoccupied with each other that she was able to approach to within just a few feet of them.

"They didn't even notice me until I yelled at the dog to get away," she said.

Steen said snakes are difficult to study in a controlled manner, so a lot about how they live and interact with each other remains a mystery.

"Something like this cool behavior — you just don't see it that often," he told Live Science. "To my knowledge, no one's ever documented two different vipers in combat before."

Steen explained that the two males were likely competing for a female that was hidden from view, adding that since the vipers are different species, they typically can't interbreed. When Steen posted the footage on YouTube, he said in the description that he and other researchers would be investigating this peculiar incident further.

"It's one observation, so we don't want to read into it too much. We don't know if it's necessarily widespread behavior," Steen told Live Science. "But it does make us want to rethink what we know about how these species interact with each other."

Original article on Live Science.

For the first time, live baby mice have been successfully produced by injecting sperm into a modified, inactive mouse embryo rather than from a fertilized egg cell, according to scientists.

Mammalian eggs that are not fertilized can be "tricked" into starting the development process toward becoming an embryo, previous research has shown. These unfertilized, slightly developed embryos are called parthenogenotes, but they die soon after they are created, due to the lack of sperm input, which triggers developmental processes.

In the new research, the scientists took these inactive embryos and injected sperm directly into them, which resulted in the birth of healthy baby mice with a success rate of up to 24 percent.

The experiment produced the first ever full-term live mice born from parthenogenotes that were injected with sperm, senior author of the study Tony Perry, a molecular embryologist at the University of Bath in England, said in a statement. [Future of Fertility Treatment: 7 Ways Baby Making Could Change]

"It had been thought that only an egg cell was capable of reprogramming sperm to allow embryonic development to take place," Perry said. "Our work challenges the dogma, held since early embryologists first observed mammalian eggs around 1827 and observed fertilization 50 years later, that only an egg cell fertilized with a sperm cell can result in a live mammalian birth."

In order to keep the parthenogenotes from perishing as they normally would, the researchers exposed them to a salt compound called strontium chloride (SrCl2). Previous research had shown that this salt encourages parthenogenetic embryos to begin normal cell division, despite not having been fertilized. The chemically modified parthenogenotes were then injected with the sperm and implanted into surrogate mothers.

The research upended the notion that mammalian sperm cells could only transform into mature sperm cells when they were within an egg — it was thought that only the egg provided the environment for division to begin, and a complex organism to develop. But the new experiment has shown that a parthenogenote can serve the same function as an egg — under the right conditions.

The mice born from the experiment were seemingly healthy, the researchers said. Their life expectancies were similar to those of control mice that were bred traditionally, and they were able to reproduce.

However, the mice born from the parthenogenote experiment had different epigenetic signatures in their DNA, compared to mice born from traditional fertilization. Epigenetic signatures are chemical modifications that are made to a DNA code, outside of the DNA "letters" themselves. The researchers suggest that this means that different epigenetic pathways can lead to the same developmental destination.

As the research continues, reproduction techniques that use parthenogenotes and sperm could be applied to conservation efforts in the breeding of endangered animals, and help treat infertility and other reproductive issues, the researchers said.

"This is an exciting piece of research which may help us to understand more about how human life begins and what controls the viability of embryos, mechanisms which may be important in fertility," Paul Colville-Nash, from the Medical Research Council (MRC), which funded the work, said in the statement. "It may one day even have implications for how we treat infertility, though that's probably still a long way off."

The study was published online Tuesday (Sept. 13) in the journal Nature Communications. 

Original article on Live Science.

A city in Japan has announced that it will pay a large part of the cost of egg freezing for women who live there, as part of a program aimed at raising the country's low birth rate. Egg freezing is the process of extracting egg cells from a woman's ovaries and storing them for later use.

Urayasu, a city near Tokyo, will provide the currency equivalent of $850,000 over a three-year period to fund a research project on egg freezing, according to the Associated Press.

Women who take part in the program would pay just 20 percent of the total cost of freezing their eggs, or about $960 to $1,150. The total cost of the procedure in Japan is around $4,800 to $5,760. (In the United States, the price of egg freezing can range from $5,000 to more than $15,000, not including the cost of the required medications.) So far, about 12 women have started the egg-freezing process as part of the Urayasu program.

The city wants to help turn around Japan's falling birth rate, which is currently at 1.4 births per woman, according to the World Bank — one of the lowest worldwide. (The birth rate in the United States is 1.9 births per woman, according to the World Bank.) [Conception Misconceptions: 7 Fertility Myths Debunked]

Egg freezing is viewed as a way to improve women's chances of conceiving at older ages. But the procedure is far from a perfect fix. Here are five surprising facts about egg freezing.

Egg freezing is not recommended as a way for women to delay having children.

Despite a growing interest in egg freezing, the procedure is still not a recommended way for women to postpone having children, at least not in the United States.

In 2012, the American Society for Reproductive Medicine (ASRM) said there is not enough data to recommend that women freeze their eggs for the sole purpose of delaying childbearing. That's because studies are lacking "to support the safety, efficacy, ethics, emotional risks and cost-effectiveness" of egg freezing for this purpose, the ASRM said.

Still, the ASRM does recommend egg freezing for several other groups of people, including women who, for example, have cancer, and may lose their fertility during chemotherapy.

Very few women who freeze their eggs actually use them.

Fertility centers have reported that the percentage of women who freeze their eggs and then come back to use them is relatively low. In a recent study, researchers at a fertility clinic in Santa Monica, California, found that, from 2007 to 2012, 232 women froze their eggs at the clinic to delay childbearing, but 95 percent of these women still had not used their eggs by 2015.

In a survey of 49 of these women, 16 percent said they were able to have children by other means, 30 percent said they were still not ready to have children and 53 percent said they hadn't used the eggs yet because they were still single.

Pregnancy is still not a guarantee with egg freezing.

Many women who freeze their eggs say they think of the procedure as an "insurance policy" in case they aren't able to become pregnant at older ages. But freezing eggs does not guarantee pregnancy success. Studies conducted in Europe on frozen eggs from donors under age 30 found that women's pregnancy rates ranged from 36 to 61 percent.

The chances of pregnancy depend, in part, on how old women are when they freeze their eggs, and the number of eggs they freeze. An online fertility calculator developed by researchers at New York Medical College and the University of California, Davis estimates that a woman who freezes 15 eggs at age 30 has about a 30 percent chance of giving birth to a child if she uses these eggs. And a woman who freezes 25 eggs at age 30 has about a 40 percent chance of giving birth to a child, the calculator estimates.

Egg freezing works best if it's done at younger ages.

The chances of pregnancy are greater if a woman uses "younger" eggs — meaning eggs she froze in her 20s or early 30s, rather than later on, Dr. Wendy Vitek, a fertility expert at the University of Rochester Medical Center, told Live Science in an interview in June 2014.

Studies tend to find that pregnancy rates for women who freeze their eggs after age 38 are significantly lower than for those who freeze their eggs at younger ages, according to ASRM. One study from Italy found that pregnancy rates for women who had their eggs frozen after age 38 was about 10 percent.

Babies born from frozen eggs are still not that common.

It's not clear exactly how many babies have been born from frozen eggs, but by some estimates, it's in the low thousands. The procedure was first used in 1986. According to the USC Fertility Center, part of the Keck School of Medicine at the University of Southern California, about 5,000 babies have been born from frozen eggs worldwide.

Original article on Live Science.

Picky females have driven the evolution of mega sperm in males as a way to ensure that the gals will get only the best mates, new research finds.

Tiny fruit flies have record-breaking sperm cells. The sperm of Drosophila bifurca can reach lengths of 2.3 inches (5.8 centimeters), for example. Researchers have long known that the peculiarities of the female fruit fly's reproductive tract are responsible for these enormous sperm, which take a huge amount of energy to produce. Female fruit flies have a sperm-storage organ in which they hold sperm from multiple matings. In this organ, the sperm cells jockey for access to an egg in a process of postcopulatory competition.

Now, researchers have found out why this sperm-versus-sperm competition benefits females. Essentially, the need to produce huge sperm pushes low-quality males out of the mating game, leaving only the fittest males for females to choose from. This means giant sperm are similar to heavy antlers or flashy feathers: a costly expenditure to ensure males have a chance to pass on their genes. [In Photos: The World's Oldest Fossilized Sperm]

A sperm paradox

Sperm are the most varied and fastest-evolving cells in the body, said Scott Pitnick, an evolutionary biologist at Syracuse University in New York and an author of the new research, published today (May 25) in the journal Nature. Sperm cells are also unique among body cells in that they spend much of their life span in a foreign environment — the female reproductive tract. But the conditions of the female reproductive tract have been understudied, Pitnick told Live Science.

"If you want to understand all that variation, you have to look at what sperm are doing inside of females," he said.

Sperm competition is a major part of reproduction for many organisms, Pitnick said, but biologists mostly thought of this process as being like a raffle: the more tickets you buy, the more likely you are to win. In that case, males should produce massive amounts of cheap sperm in order to have the best chances of reproduction. [7 Interesting Facts About Sperm]

Giant fruit fly sperm didn't fit that mold at all. These sperm are very expensive to produce; they should also theoretically reduce competition, Pitnick said. Because fruit flies that produce mega sperm can produce only a few sperm cells at a time — as few as six per every egg females produce — this should decrease the number of sperm vying for fertilization and ease the selective pressures driving sperm size upward.

But that wasn't happening. Now, it's clearer why that is the case. Pitnick and his colleagues bred multiple lines of fruit flies with sperm "tagged" by fluorescent proteins, so researchers could tell which sperm came from which flies. In doing so, the researchers were able to determine the factors that influence when and how sperm are successful.

They found that there are strong genetic correlations between the length of the female sperm-storage organ and the length of sperm in a species such that when females evolve longer sperm-storage organs, males automatically produce longer sperm.

Meanwhile, females with longer sperm-storage organs also evolve to mate more frequently, which heightens the sperm war going on in their reproductive tracts. This means that even bigger sperm are likely to win the battle and go on to produce offspring. Only the highest-quality males can keep up in this cycle of sperm competition, so low-quality males get pushed out of the mating game. Females thus get the pick of the litter as far as genetics for their offspring.

Antlers, feathers and … sperm?

The findings explain why competition continues even as there are fewer sperm to compete, Pitnick said.

"As sperm length evolves, you get all this weird self-reinforcement that keeps driving it further and further along," he said.

The findings also reveal that though female fruit flies "choose" sperm simply based on the size of their own storage organs, the process works much like the sexual selection that occurs for flashy male ornamentation such as peacock tails or deer antlers, the researchers said. In fact, the selection is stronger than for many classic sexually selected traits such as lizard horns or the enormous jaws of stag beetles.

The parallel between sexual selection for giant sperm and sexual selection for other traits is useful, Pitnick said, because the mechanism by which females "pick" sperm is simple anatomy, not complex cognition.

"We have a simple physiological basis where you can actually look at the genetics of female choice," he said. "When people think about sex differences, they should be thinking about not just plumage and antlers and courtship dances. They should [also] be thinking about sperm and female reproduction tracts."

Follow Stephanie Pappas on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

People who eat fast food may be ingesting potentially harmful chemicals called phthalates, a new study finds — another reason to avoid eating these typically unhealthy foods, experts say.

However, experts emphasize that most Americans are exposed to phthalates every day, and it's not clear exactly how much of this exposure comes from fast food.

Still, for people who want to reduce their exposure to phthalates, a chemical used in plastics that can leach into foods, reducing fast food consumption could be one way to do this, said Dr. Kenneth Spaeth, chief of occupational and environmental medicine at Northwell Health, a health care network headquartered in Great Neck, New York.

"I think there are very pressing health reasons to avoid fast food to begin with," including its ties to obesity, said Spaeth, who was not involved in the new study on phthalates. "Now, with this kind of information about phthalates [linked to fast food], that certainly becomes an additional reason" to avoid these foods, Spaeth said. [12 Worst Hormone-Disrupting Chemicals & Their Health Effects]

In the study, public health researchers at The George Washington University in Washington, D.C., analyzed information from more than 8,800 people who took part in a national health survey and answered questions about their diet, including how much fast food they'd eaten in the past day. The survey participants also submitted urine samples, which the researchers analyzed to look for the breakdown products of two types of phthalates.

The results showed that the people who had eaten the most fast food in the past day had levels of phthalate metabolites that were 24 to 40 percent higher than those of the people who hadn't eaten fast food, the study found.

The findings are concerning, Spaeth said, because exposure to phthalates has been linked with adverse health effects, including reproductive problems in adults, and lower IQ in children. Although previous studies have shown that phthalates come from many sources, and that 98 percent of Americans have detectable levels of the chemicals, the new study suggests that fast food could be a "meaningful source" of phthalates, Spaeth said.

The findings are also impactful because they implicate a popular food category as a potential source of people's phthalate exposure. "You clearly see that the sources of exposure are not subtle," Spaeth said.

The study also suggested that meat and grain items — including bread, cake, pizza, burritos, rice dishes and noodles — were the biggest contributors to phthalate exposure in the people who ate fast food.

Phthalates might get into fast food if the food comes into contact with plastic packing or PVC tubing (used in food processing) that contains the chemical. It's also possible that the plastic gloves that fast food workers wear may be a source of phthalates, the researchers said.

It's hard for people to avoid exposure to phthalates altogether, Spaeth said, because the chemicals are found in a lot of consumer products, including cosmetics and personal care products, and other processed foods.

It's important to note that the study found only an association between fast food consumption and exposure to phthalates in people, and does not prove that the phthalates actually came from fast food. Future studies are needed that take into account other sources of phthalates, including other processed foods, to better understand the role of fast food in phthalate exposure, Spaeth said.

The study was published April 13 in the journal Environmental Health Perspectives.

Follow Rachael Rettner @RachaelRettner. FollowLive Science @livescience, Facebook& Google+. Original article on Live Science.

As any parent knows, keeping tabs on your developing young in a dangerous world can be a trial. A tiny, resourceful creature that lived 430 million years ago devised a novel method for such baby tracking: It tethered egg pouches to its back with threads and trailed its juveniles as they grew, as if they were tiny kites.

Scientists recently described the arthropod —  a type of invertebrate with a segmented body and exoskeleton — and its unusual parenting practice in a new study, with the animal's kitelike appendages inspiring them to name the specimen after "The Kite Runner," a popular 2003 novel by Khaled Hosseini.

The first part of its scientific name, Aquilonifer spinosus, is derived from the Latin words aquila (eagle or kite) and fer (carry). [Video: Ancient 'Kite Runner' Creature Flew Its Young on Strings]

"Like Pompeii on the ocean floor"

Eyeless, flat-bodied A. spinosus measured less than 0.5 inches (1.3 centimeters) long. A shield protected its head, which was topped by two sweeping antennalike structures, and it used its 12 pairs of legs to scuttle across the sea bottom in what is now Herefordshire in the U.K. The region looks very different today — for one, it's not underwater anymore — but fossils of numerous small creatures like A. spinosus that once inhabited the ocean are preserved in outcrops inside rocky spheres, "like baseballs," of hardened volcanic ash called concretions, which formed around their remains, said Derek Briggs, a paleontology professor at Yale University and lead author of the study.

"The tendency is to think of this as Pompeii on the ocean floor," Briggs said.

Typically, each concretion holds a single fossil, which is usually too small to be chipped out of the rock. Scanning methods that typically help paleontologists reconstruct embedded fossils aren't much use for these specimens, he said, because their mineral composition is too similar to the concretion around them for the scans to distinguish between the two.

Destroying to preserve

So Briggs turned to the only surefire way to study these tiny fossils in three dimensions: He and his colleagues split open each concretion and cut out the rock holding the fossil. Then, they ground away slices of the embedded specimen, each just microns (millionths of a meter) thick, and photographed each to rebuild the fossil as a digital model — a process that took many hours.

Though grinding destroys the original specimen, the results are worth it because they yield a highly detailed model that can be studied from any angle and can be reproduced multiple times, Briggs said.

And what Briggs and his colleagues found when they reconstructed their "Kite Runner" was something they had never seen before: an arthropod trailing strings attached to 10 flattened pods that appeared to contain juveniles.

In the false-color digital reconstruction, the little legs of the baby kite runners could be seen as traces of bright green in and immediately around the pods. The scientists counted approximately six limbs on the juveniles — half as many legs as the adult form, perhaps because the young were still developing, Briggs said.

Though it's possible that these pods contained hitchhikers or parasites, it's less likely, Briggs added. A. spinosus had long, antennalike structures on its head that could have been used to sweep away pesky stowaways, he proposed. And the threads were tethered to body spines — an inefficient feeding path for a parasite, which typically prefers to latch on close to the host's body.

This unique discovery suggests that arthropods during this period were still experimenting with methods of brooding their young. In fact, some of these approaches — like carrying young directly on their backs — are used by species alive today, though this particular "kite" method is not.

And according to Briggs, there are likely many more fossil surprises tucked away in numerous concrete spheres from this site that are yet to be discovered.

"Many of these things are unique; it's the only place they're found in the fossil record," he said. "They tend, for that reason, to reveal details about particular groups and how they evolved that are just not available anywhere else."

The findings were published online today (April 4) in the journal Proceedings of the National Academy of Sciences.

Follow Mindy Weisberger on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Does the size of your brain say anything about your smarts?

Plenty of brainy scientists have pondered the link between a person or animal's grey matter and their cognitive skills.

Perhaps fitting for a question about the human brain — which packs in more than 100 billion neurons, according to the National Institutes of Health — but the answer is mired in complexities and unknowns. 

For one, scientists still debate over the definition of intelligence. For any IQ definition, how do you measure it? Further, do differences in IQ show up in daily life? And finally, does more brain tissue or a heftier brain equate with higher IQ?

One thing scientists do agree on: A big brain alone doesn't equate with smarts. If it did, elephants and sperm whales would win all the spelling bees. Rather, scientists look at brain mass relative to body mass in order to make any speculation about a creature's cognitive abilities.

So while an elephant noggin, at 10.5 pounds (4,780 grams), could squash a human think box in a purely physical battle of brains, you and I take the cake in a war of wits. Our brains, which weigh an average of 2.7 pounds (1,200 grams), account for about 2 percent of body weight, compared with an elephant's under one-tenth of a percent.

Studies have shown that across species relatively large brains "do seem to provide some complex cognitive skills, such as innovative solutions to ecological problems, more efficient resource mapping and food acquisition, and more complex social strategies (such as deception)," said Nancy Barrickman, a graduate student in Duke University's Department of Biological Anthropology and Anatomy.

A study by Sarah Benson-Amram, of the University of Wyoming in Laramie, and her colleagues revealed experimental data linking animal smarts with relative brain size. In that study, detailed Jan. 25, 2016, in the journal Proceedings of the National Academy of Sciences, the researchers gave 140 zoo-dwelling mammalian carnivores, from 39 different species, a tasty problem to solve. The animals had to open an L-shaped latch to open a box and grab the treat inside. They found that animals in the bear family did best, while two species of mongoose never managed to open the latch.  After accounting for other factors that could led to successful latch-opening, such as manual dexterity and sociality, the researchers concluded that relative brain size was the most significant predictor of success in the task.

Differences in brain size within a species, such as humans, are relatively small, making it difficult to tease out the effects of brain size and the effects of other factors. For instance, the difference in intelligence between an individual with, say, a brain that's 1,100 grams and one that's 1,400 grams (which could be found in humans) is confounded by other variables, including differences in density of neurons, other structural brain differences and socio-cultural factors.

Take genius Albert Einstein, who's brain was not significantly bigger than the average human's. Rather, some scientists have found, his ability to grasp mind-boggling concepts and make seemingly impossible mental leaps may have come down to connections. Turns out, his noggin was likely highly integrated so that several paths would have connected distant regions to one another. [What If Humans Were Twice as Intelligent?]

And the debate continues …

Brain size seems to have nothing to do with scores on standardized intelligence tests, according to a brain-scan study of young children.

Michael McDaniel, an industrial and organizational psychologist at Virginia Commonwealth University, has claimed that bigger brains do make for smarter people. Many researchers, however, disagree with McDaniel's conclusion. His research, published in 2005 in the journal Intelligence, suggested that across all age groups and sexes, brain volume is linked to intelligence.

Men are smarter than women, according to research published in 2006, which the study researchers say could be due to men having relatively larger brains, a difference of about 0.2 pounds (100 grams). Another scientist put forth several socio-cultural factors that would make the men-smarter results null.

Average brain weights for primates (not relative to body size):

• Chimpanzee (Pan troglodytes) — 0.77 pounds (350 grams)
• Mountain gorilla (Gorilla gorilla beringei) — 0.95 pounds (430 grams)
• Mouse lemur (Microcebus murinus) — 0.004 pounds (2 grams)

Sizing up brains for the rest of the animal kingdom, would include:

• Sperm whale — 17 pounds (7,800 grams)
• Walrus — 2.4 pounds (1,100 grams)
• Domestic cat — 0.06 pounds (30 grams)

If brain size had anything to do with innovation and creativity, some scientists expected to see a link between the so-called Mind's Big Bang (the emergence of bone tools and cave paintings that occurred between 50,000 and 70,000 years ago) and the emergence of modern-size human brains. Not the case.

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A man's weight may affect the heritable information that is carried in his sperm, according to a small new study from Denmark.

The results may provide a biological clue as to why children of obese fathers may be predisposed to being obese, the researchers said. The information in the sperm cells that varied depending on the weight of the men in the study was "epigenetic" information, meaning it helps to determine how much or how often certain genes become activated. (In contrast, "genetic" information denotes variation in the genes themselves.)

"In our study, we found that obese men had different epigenetic signals in their sperm cells compared to lean men, and these signals were carried on genes important for the development of the brain and the regulation of appetite," said study author Romain Barrès, an associate professor of integrative physiology at the University of Copenhagen.

In the study, the researchers compared epigenetic markers in the sperm of 13 lean men with those of 10 obese men. They found that the sperm of the obese men carried a different epigenetic signature compared to that of the lean men, particularly at genes that are involved in controlling the development and functioning of the brain. [8 Reasons Our Waistlines Are Expanding]

In a separate part of the study, the researchers looked at six obese men who underwent weight-loss surgery, in order to see how the surgery might have changed the hereditary information in their sperm. The researchers found an average of 5,000 structural changes in sperm cell DNA between the time before the men underwent surgery and a year after the surgery. These changes were associated with genetic locations that had been implicated in controlling appetite, the scientists found.

More research is needed to examine what these changes may mean and how they may affect a man's children, but the new data provides early evidence that sperm carries information about a man's health, the researchers said.

"Our research could lead to changing behavior, particularly preconception behavior of the father," Barrès said in a statement. "It's common knowledge that when a woman is pregnant, she should take care of herself— not drink alcohol, stay away from pollutants, etc. — but if the implication of our study holds true, then recommendations should be directed towards men, too."

The researchers said they think there may be evolutionary reasons why hereditary information about a father's weight could benefit his children. This information "could be useful for species to better adapt from one generation to the next," Barrès said.

For example, when food is abundant, it may be beneficial for children to eat more and grow bigger, he said.

"As a species, being able to store as much energy (fat) as possible has long been an advantage to resist famine or infections," Barrès told Live Science. "It [is] only very recent in human history that being obese is a disadvantage, with higher predisposition to cardiometabolic, musculoskeletal diseases, diabetes and cancer."

The new study was published today (Dec. 3) in the journal Cell Metabolism.

Follow Agata Blaszczak-Boxe on Twitter. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.