A deep-sea expedition off the coast of Argentina has captured stunning footage of more than 40 never-before-seen species.

One unexpected star of the show is a plump sea creature that has been dubbed the "big-butt starfish" for its uncanny resemblance to Patrick Star from "SpongeBob SquarePants."

During the remotely operated vehicle (ROV) SuBastian's dives in Argentina's Mar del Plata submarine canyon, which have been running since July 23, scientists aboard its accompanying research vessel provide a high-definition livestream, with real-time commentary on rarely seen deep-sea life. The dives have revealed carnivorous sponges, translucent fish, vividly colored rays and corals that have never been documented in the South Atlantic, a biodiversity hotspot that remains largely unexplored.

The sea star, which has become a viral hit on social media, belongs to the genus Hippasteria, which is known for its thick central disc and short, stubby arms. During the livestream, viewers interacting via chat affectionately nicknamed it "estrella culona" — Spanish for "big-butt star."

Argentine scientists involved with the expedition have offered a few hypotheses for the creature's attention-grabbing anatomy. The starfish may simply be well fed; they are voracious carnivores. Or, its rounded appearance could be the result of gravity, as it was filmed on a vertical surface with its central disc hanging downward, creating the illusion of glutes.

Starfish don't have rear ends like humans or other bilaterally symmetrical animals do. Instead, they exhibit radial symmetry, with a mouth located on the underside of the central disc. That lower, or "oral," surface lies pressed against the seafloor, where feeding occurs. The anus is located in the center of the upper, or "aboral," surface, which is what a diver would see first when approaching the animal.

Related: 'A disembodied head walking about the sea floor on its lips': Scientists finally work out what a starfish is

"Although starfish do have a complete digestive system and an anus, it's not in the location people are pointing to on social media," Mariela Romanelli, a biologist and curator of the invertebrate collection at Argentina's National Museum of Natural Sciences, told local news site Infobae in Spanish. "Still, the resemblance to Patrick Star's butt is pretty hilarious."

The big-butt starfish isn't the only creature from the expedition, led by scientists from the National Scientific and Technical Research Council and the Schmidt Ocean Institute, that has charmed the public. Another deep-sea creature captured on camera was a violet sea cucumber, belonging to the genus Benthodytes, whose plump body and purple hue earned it its name "Batatita"" ("Little Sweet Potato"). The specimen was collected by the ROV and is alive and well at the surface, expedition scientists said.

So far, the expedition has documented at least 25 species of fish, both bony and cartilaginous; carnivorous sponges that have never been recorded in the South Atlantic; and crustaceans and other invertebrates that are specially adapted to the pitch-black depths.

The livestream, broadcast for the first time from nearly 13,100 feet (4,000 meters) below sea level, continues through Aug. 10 and can be viewed on the Schmidt Ocean Institute's official YouTube channel.

The face of a car-size, millipede-like creature — the largest arthropod ever to live — has finally been revealed thanks to two well-preserved fossils, a new study reports.

The arthropod, Arthropleura, lived in forests near the equator between 346 million and 290 million years ago, during the late Paleozoic era. In the oxygen-rich atmosphere at that time, Arthropleura could grow to a massive 8.5 feet (2.6 meters) long and weigh over 100 pounds (45 kilograms).

"Arthropleura … has been known since the 18th century, over 100 years, and we hadn't found a complete head," study first author Mickaël Lheritier, a paleontologist at Claude Bernard Lyon 1 University in France, told Live Science. "Now with the completed head, you can see the mandibles, the eyes, and these characteristics can [help us understand] the position of this [creature] in evolution."

The giant arthropod had perplexed paleontologists for decades. Arthropleura's body had characteristics like a millipede. But without the head, scientists couldn't understand the creature's relationship to modern arthropods like millipedes and centipedes. While these two modern creatures may look similar, they actually diverged about 440 million years ago, way before Arthropleura came around. Paleontologists wondered if Arthropleura was a member of the millipede group or the centipede group.

Arthropleura's family-tree controversy "features fierce debates about its affinities," James Lamsdell, a paleontologist at West Virginia University who was not involved with the study, wrote in an accompanying perspective published in the same journal. But with the discovery of an intact head, "the mystery of Anthropleura now appears solved."

Related: 7-foot-long arthropods commanded the sea 470 million years ago, 'exquisite' fossils show

The CT scans virtually uncovered the fossilized head of two juvenile Arthropleura discovered within rock in the Montceau-les-Mines Lagerstätte fossil site in France. The CT scans revealed unique stalked eyes jutting from the side of the head; gently curved antennae; and small, centipede-like mandibles. Together, these traits made up a confusing amalgamation of centipede- and millipede-like characteristics.

"These details, together, may appear to leave Arthropleura as much — if not more — a puzzle than before," Lamsdell said. "But the seemingly chimeric nature of Arthropleura is actually important evidence that may help answer a fundamental question regarding the [evolution of these species]."

Based on anatomical features, paleontologists ultimately grouped Arthropleura as most closely related to the millipede family. However, the stalked eyeballs have never been seen in the millipede or centipede families. Arthropleura has been widely considered terrestrial, but eyestalks are typically found in semiaquatic or fully aquatic animals, like crustaceans.

Because the head belongs to a juvenile, the explanation might lie in the animal's life stage, Lamsdell suggested. As juveniles, Arthropleura may have spent more time in the water, before losing the stalked eyes in adulthood. "The stalked eyes remain a big mystery, because we don't really know how to explain this," Lheritier said.

Using LED lights and glow sticks, scientists in the Bahamas have discovered an ancient deep-sea crustacean with giant eyes and a see-through body. 

Although the species, which they named Booralana nickorum, is newly identified, it has been on the planet for 300 million years and may play a crucial role in maintaining the health of the ecosystem, the researchers wrote in a study published Jan. 12 in the journal Zootaxa.

The new species has a hard exoskeleton; a segmented body; and big, compound eyes to find potential prey. As it lives in the deep sea, where there's very little light, it has no need for color or pigmentation, so it's white, and even slightly translucent. 

"You can see its guts and things," study co-author Nicholas Higgs, director of research and innovation at the Cape Eleuthera Institute, told Live Science.

Related: Creepy deep-sea 'vanilla Vader' woodlouse is 25 times bigger than a land louse 

At around 2.2 to 3 inches (55 to 76 millimeters) long, it's much larger than its terrestrial cousins in the pill bug family — also called roly poly bugs or woodlice — which measures around 0.55 inch (14 mm). B. nickorum's large size gives the deep-sea scavenger an advantage as it waits on the seabed for food to fall from above. 

"The bigger you are, the more you can get from any one meal," Higgs said, and the longer the animal can last between meals, which is important in this environment, where food is scarce. 

The team discovered B. nickorum at depths of between about 1,770 and 1,840 feet (540 to 560 meters) on an underwater slope in the Bahamas' Exuma Sound. They obtained the specimens during two expeditions, in April 2014 and February 2019, operated by OceanX and the Cape Eleuthera Institute. In 2014, they put down baited eel traps, which caught deep-sea isopods — a type of crustacean with a flattened, segmented body — so they returned in 2019 to investigate further using light traps. Instead of bait, these units had a flashing, multicolor LED fishing light; a green glow stick: a green, deep-drop LED fishing light; and a programmable white LED light to attract creatures by mimicking the bioluminescence generated by deep-sea animals. 

As soon as the researchers examined the specimens on board the ship, they were confident that the species was "definitely different from anything we've seen before," Higgs said. 

Further tests confirmed that B. nickorum was a new species. It was named after two members of senior author Edward Brooks' family, both called Nicholas Brooks.

These isopods play a critical role in the ecosystem by speeding up the decomposition of plant or animal matter so the wider ecosystem can benefit from these energy sources. "Otherwise, it would just sink down and remain locked away in the sediment," Higgs said.

These crustaceans also ensure that the carbon within the organic matter falling from the shallows is captured in the deep ocean for thousands of years. 

Finding new species like these helps researchers understand whether animals in the deep ocean are endemic to one place or disperse from one region to another over time. This enables scientists to better predict the ripple effect of human activities, such as mining. "If you impact one site, is that going to impact animals in a different area?" Higgs said.

With more countries like the Bahamas considering deep-sea oil exploration, Higgs believes expeditions like these are vital in helping decision-makers understand how drilling could affect their precious ecosystems. 

"As long as we don't have access to this environment," he said, "we're not going to appreciate it, we're not going to understand it, and we're not going to value it.”

Scientists have finally figured out where caterpillars got their extra sets of legs from. Turns out, these chubby little limbs originate from their crustacean ancestors over 400 million years ago.

Insects have six legs, except when they don't. Caterpillars — the larvae of butterflies and moths — have additional sets of limbs known as prolegs. So do the larvae and even adults of a handful of other insects. These prolegs pose an evolutionary mystery, and scientists have long grappled over how and why they got them.

A new study published Oct. 12 in Science Advances suggests these prolegs have origins in the primitive crustaceans that insects evolved from during the Ordovician period (485.4 million to 443.8 million years ago).

Prolegs are unjointed and feature sets of gripping hooks that function like spiky suction cups. Some species have as many as nine pairs. Unlike the six legs that most insects have, which extend from the thorax, or midsection, prolegs emerge from the abdomen. Their movement is mostly powered by hydraulic pressure — the movement of liquid into each limb.

Related: Fuzzy caterpillar has sting 'like being hit with a baseball bat," and now we know why

"Caterpillars are just eating tubes. They are maximizing their eating and growth potential. So they have evolved a gut-based body plan with a few legs to support the gut," co-author Antonia Monteiro, an evolutionary biologist at the National University of Singapore (NUS), told Live Science.

"Prolegs help them either grab onto substrates while the other legs help them feed or move them along the substrate," she said. After the caterpillar metamorphoses, the prolegs disappear. "When you become an adult insect, you don't need them. You have a beautiful body plan with massive wings and you just don't need those little gut supports. You have a different lifestyle."

Scientists have previously proposed that prolegs relate to thoracic legs — saying they are extra sets of legs that disappeared over the span of insect evolution and were reactivated when they became useful again. Others believe they are completely novel adaptations. 

A third hypothesis is that they are modified endites — internally facing leg structures that were apparent in ancestral crustaceans.

In the new study, the scientists tested the manner in which genes direct the growth of these appendages by altering the embryonic development of squinting bush brown butterflies (Bicyclus anynana). In doing so, they hoped to determine which of these hypotheses — if any — was valid.

By disrupting a gene that stipulates the placement of limbs and other structures while the larva is still in the embryonic stage, the researchers were able to elucidate the pathways by which prolegs develop. When the gene was partially disabled, precursors to typical legs as well as prolegs developed on the caterpillar's abdominal segments. When it was fully disabled, only the precursors to typical legs were present. 

Because both types of limb were present when the gene was partially disabled, the researchers demonstrated that prolegs do not develop from the same types of cells as thoracic legs. 

Rather, they seem to be modified endites. As crustaceans evolved into insects, endites were largely lost. But in butterflies and moths, the gene for them got reactivated, providing caterpillars with their prolegs.

The only other place that endites appear to persist in insects is in the mouthparts — the mandibles, maxillae and labium, which are actually modified legs themselves. The cutting edge of the mandible, for example, seems to be a highly modified endite.

"Prolegs have a lot of affinities with the head appendages in terms of the cocktail of genes that they express," Monteiro said.

So, structures that trace back to the crustacean ancestors of insects have been evolutionarily repurposed multiple times and for multiple functions — helping very hungry caterpillars move their ponderous bodies and sate their formidable appetites.

More than 10 billion snow crabs recently vanished from the Bering Sea, and now we know why: They fell victim to one of the biggest marine heat wave die-offs on record, new research shows.

The deadly heat wave, which struck polar waters between Alaska and Siberia in 2018 and lasted for two years, triggered record-high ocean temperatures and historic declines in sea ice. These "unprecedented" circumstances brought a large population of snow crabs (Chionoecetes opilio) living in the eastern Bering Sea to its knees, according to a new study, published Thursday (Oct. 19) in the journal Science. 

"The collapse of the snow crab population was a strong response to a marine heatwave," researchers wrote in the study. Rather than succumbing directly to warm ocean temperatures, however, it appears the crabs died of starvation.

Snow crabs are small, round-shelled crustaceans that can live for up to 20 years on soft seabeds that are less than 650 feet (200 meters) deep, according to the National Oceanic and Atmospheric Administration (NOAA). The species is closely monitored and managed in the eastern Bering Sea due to its commercial value as seafood.

Related: Why do animals keep evolving into crabs?

Scientists first noticed a dramatic drop in the number of snow crabs during a survey in 2021, which "found the fewest snow crab on the eastern Bering shelf since the survey began in 1975," researchers wrote in the study. No survey was conducted in 2020 due to the coronavirus pandemic, which is why scientists only noticed the crabs had disappeared the following year. But until now, the cause of the population collapse remained a mystery.

It turns out that warm water temperatures caused by the heat wave probably affected the metabolism of the crabs and increased their caloric needs, according to the study. Previous research conducted in a laboratory found that snow crabs' energy requirements doubled when water temperatures rose from 32 degrees to 37.4 degrees Fahrenheit (0 degrees to 3 degrees Celsius). This jump in temperature is equivalent to the change experienced from 2017 to 2018 by juvenile snow crabs, which live in frigid waters known as the "cold pool" and migrate to warmer spots as they mature, according to the study.

Snow crabs' increased caloric needs were reflected by a change in body size between 2017 and 2018, with smaller crabs caught during a survey after the heat wave had begun, according to the study.

The snow crabs also fell victim to bad timing. Right around the time of the heat wave, the crab population in the eastern Bering Sea had boomed, according to the study. The combination of more crabs and higher caloric needs proved deadly.

Other factors — such as predation by Pacific cod (Gadus macrocephalus), cannibalism of smaller crabs by larger ones, fishing and disease — likely contributed to the mortality event, but "temperature and population density were the key variables in the recent collapse," they added. 

The effects of rapidly rising ocean temperatures and more frequent heat waves in response to climate change are difficult to predict, researchers wrote in the study, but the snow crab die-off is "a prime example for how quickly the outlook can change for a population."

And while the future of snow crabs in the eastern Bering Sea is now "precariously uncertain" as they haven't recovered from the mortality event, the population may eventually find refuge in colder waters further north. How the mass death might affect the wider ecosystem remains unclear.

"The problems currently faced in the Bering Sea foreshadow the problems that will need to be confronted globally," the researchers wrote. "The disappearance of snow crab will be a staggering blow to the functioning of some communities in rural Alaska, such as those on St. Paul Island, which rely strongly on the revenue derived from the capture and processing of snow crab."

A flat, rounded shell. A tail that's folded under the body. This is what a crab looks like, and apparently what peak performance might look like — at least according to evolution. A crab-like body plan has evolved at least five separate times among decapod crustaceans, a group that includes crabs, lobsters and shrimp. In fact, it's happened so often that there's a name for it: carcinization.

So why do animals keep evolving into crab-like forms? Scientists don't know for sure, but they have lots of ideas.

Carcinization is an example of a phenomenon called convergent evolution, which is when different groups independently evolve the same traits. It's the same reason both bats and birds have wings. But intriguingly, the crab-like body plan has emerged many times among very closely related animals. 

The fact that it's happening at such a fine scale "means that evolution is flexible and dynamic," Javier Luque, a senior research associate in the Department of Zoology at the University of Cambridge, told Live Science.

Related: Does evolution ever go backward?

Crustaceans have repeatedly gone from having a cylindrical body plan with a big tail — characteristic of a shrimp or a lobster — to a flatter, rounder, crabbier look, with a much less prominent tail. The result is that many crustaceans that resemble crabs, like the tasty king crab that's coveted as a seafood delicacy, aren't even technically "true crabs." They've adopted a crab-like body plan, but actually belong to a closely related group of crustaceans called "false crabs."

When a trait appears in an animal and sticks around through generations, it's a sign that the trait is advantageous for the species — that's the basic principle of natural selection. Animals with crabby forms come in many sizes and thrive in a wide array of habitats, from mountains to the deep sea. Their diversity makes it tricky to pin down a single common benefit for their body plan, said Joanna Wolfe, a research associate in organismic and evolutionary biology at Harvard University.

Wolfe and colleagues laid out a few possibilities in a 2021 paper in the journal BioEssays. For example, crabs' tucked-in tail, versus the lobster's much more prominent one, could reduce the amount of vulnerable flesh that's accessible to predators. And the flat, rounded shell could help a crab scuttle sideways more effectively than a cylindrical lobster body would allow.

But more research is needed to test those hypotheses, Wolfe said. She is also trying to use genetic data to better understand the relationships among different decapod crustaceans, to more accurately pinpoint when various "crabby" lineages evolved, and pick apart the factors driving carcinization.

There's another possible explanation: "It's possible that having a crab body isn't necessarily advantageous, and maybe it's a consequence of something else in the organism," Wolfe said. For example, the crab body plan might be so successful not because of the shell or tail shape itself, but because of the possibilities that this shape opens up for other parts of the body, said Luque, who is a co-author of the 2021 paper with Wolfe.

For example, a lobster's giant tail can propel the animal through the water and help it crush prey. But it can also get in the way and constrain other features, Luque said. The crab body shape might leave more flexibility for animals to evolve specialized roles for their legs beyond walking, allowing crabs to easily adapt to new habitats. Some crabs have adapted their legs for digging under sediment or paddling through water.

"We think that the crab body plan has evolved so many times independently because of the versatility that the animals have," Luque said. "That allows them to go places that no other crustaceans have been able to go."

The crab-like body plan also has been lost multiple times over evolutionary time — a process known as decarcinization.

"Crabs are flexible and versatile," Luque explained. "They can do a lot of things back and forth."

Wolfe thinks of crabs and other crustaceans like Lego creations: They have many different components that can be swapped out without dramatically changing other features. So it's relatively straightforward for a cylindrical body to flatten out, or vice versa. But for better or worse, humans won't be turning into crabs anytime soon. "Our body isn't modular like that," Wolfe said. "[Crustaceans] already have the right building blocks."

Triops are a group of freshwater crustaceans commonly called tadpole shrimp or dinosaur shrimp. They look like ancient armored tadpoles, a look they've rocked for hundreds of millions of years. The word "Triops" means "three eyes" in Greek, and the group is so named because they have two main compound eyes and a third simple organ called an ocellus eye that helps them detect light. 

The animals are not shrimp, which is a name usually reserved for marine crustaceans in the order Decapoda (Triops are in the order Notostraca). But like shrimp, Triops — one of two genera in its own family and order — live in water. In fact, Triops have adapted to an extreme life in temporary freshwater or slightly salty pools that may only last a few weeks before drying out.

Are Triops dinosaurs?

Triops' appearance hasn't changed much since the group first emerged in the Devonian period (419 million to 359 million years ago), according to Central Michigan University in Mount Pleasant, Michigan. This ancient and morphologically consistent lineage led some people to call the creatures "living fossils," a term that's also commonly used to describe deep-sea fish called coelacanths (SEE'-lah-kanths) and horseshoe crabs — another animal that looks a bit like Triops. 

Scientists used to consider one Triops species, Triops cancriformis, as being the same animal seen in 250 million-year-old fossils. That would mean Triops cancriformis had survived to the present day from the Triassic period (about 252 million to 201 million years ago) when dinosaurs first emerged — hence the name "dinosaur shrimp." However, a 2013 study of Triops DNA published in the journal PeerJ found that the current species evolved within the last 25 million years. 

"Living fossils evolve like any other organism, they just happen to have a good body plan that has survived the test of time," study lead author Africa Gómez, an evolutionary biologist at the University of Hull in England, said in a statement at the time. "A good analogy could be made with cars. For example, the Mini has an old design that is still selling, but newly made Minis have electronic windows, GPS and airbags: in that sense, they are still 'evolving', they are not unchanged but most of the change has been 'under the hood' rather than external."

Related: This 'ancient' monster fish may live for 100 years

Where do Triops live?

The Triops group is found on every continent except for Antarctica. The Integrated Taxonomic Information System (ITIS) recognizes 13 different species in the Triops genus, including the Australian tadpole shrimp (Triops australiensis) in Australia, Triops emeritensis in Europe and northern Asia, and Triops maximus in Africa. The U.S. has two native species: Newberry tadpole shrimp (Triops newberryi) and summer tadpole shrimp (Triops longicaudatus). 

Summer tadpole shrimp have the widest distribution of all the Triops species and are found throughout the U.S. (except for Alaska), Canada, the Caribbean, Japan and some Pacific Islands, though humans likely introduced them to Japan and the Pacific Islands, according to the University of Michigan's BioKids website. 

How big do Triops get?

Triops usually grow to be no more than a few inches in length. For example, summer tadpole shrimps reach about 1.6 inches (4 centimeters) long, and this is still considered quite large for Triops, according to BioKids. Australian tadpole shrimp are larger and max out at about 3.5 inches (9 cm) long, according to the Western Australian Museum.  

How do Triops breed?

Because Triops' water habitats are only temporary, they mature quickly and go from eggs to breeding adults in two to three weeks, according to Buglife, an invertebrate conservation charity in the U.K. Triops are hermaphrodites, which means each individual has both sexual organs, but they can also reproduce sexually and even produce offspring from unfertilized eggs. This flexibility when it comes to reproducing helps each generation of Triops give rise to another in extreme environments, including deserts. 

Triops' eggs may enter "diapause," which is a state of dormancy in which the eggs stop developing and dry out. Diapause allows the eggs, and the Triops inside, to survive when their watery pools evaporate in arid conditions. The eggs may stay in diapause for up to 27 years, waiting for water to return so they can hatch, according to Buglife. 

Related: 100 million-year-old fairy shrimp reproduced without sex, rare fossils reveal

When conditions are favorable, these animals can suddenly hatch in large numbers. For example, hundreds of Triops emerged in an ordinarily dry ceremonial ball court — a circular walled structure — at Wupatki National Monument in northern Arizona in 2021, Live Science previously reported. 

"We knew that there was water in the ball court, but we weren't expecting anything living in it," Lauren Carter, lead interpretation ranger at Wupatki National Monument, told Live Science at the time. "Then a visitor came up and said, 'Hey, you have tadpoles down in your ballcourt.'" 

The "tadpoles" were Triops that hatched after a monsoon created a temporary lake in the ball court. After they've hatched, Triops live up to 70 days in the wild and 90 days in captivity, according to BioKids. 

What do Triops eat

Triops are very adaptable and have a varied diet that includes scavenging floating organic material in their pools and hunting things like zooplankton and insect larvae. When food is scarce, they may even eat each other. Summer tadpole shrimps are a pest in rice fields because they eat young crops and make crop water muddier so less light reaches the plants, according to Central Michigan University.

Birds, especially waterfowl, eat Triops. The threat of predation is so great for Triops that they tend to be solitary, because potential predators are more likely to see and eat a group of them, according to BioKids. 

Are Triops endangered?

Four species of Triops face extinction, according to the International Union for Conservation of Nature (IUCN): Triops gadensis, Triops baeticus and Triops vicentinus are endangered and Triops emeritensis is critically endangered. All four species live on the Iberian Peninsula in Spain and Portugal, and are threatened by human activities such as development and agriculture. 

The IUCN hasn't assessed either of the species found in the U.S. However, Newberry tadpole shrimps are classified as "secure" — not at risk of extinction — according to NatureServe, a non-profit based in Virginia that collects data on North American wildlife.  

Additional resources

To view a map of where Triops is found across the world, check out the Encyclopedia of Life website. To learn more about how Triops longicaudatus survive in the U.S., watch this short YouTube video by Zion National Park. For more information about Triops, check out "Timeless Triops: A Prehistoric Creature" (Lori Adams Photo, 2014).

Originally published on Live Science.

A number of marine animals — including octopuses, squids, crabs and lobsters — will be recognized as sentient beings as part of a new law proposed by the U.K. government.

The Animal Welfare (Sentience) Bill was first proposed in May and is currently under review. The proposed law originally included all vertebrates, or animals with a backbone, but no invertebrates. However, on Nov. 19, the U.K. government announced that two invertebrate groups — cephalopod mollusks (octopuses, squids and cuttlefish) and decapod crustaceans (crabs, lobsters, shrimp and crayfish) — will now be included on the list of sentient beings, which means their welfare will have to be considered when future government decisions are made about them..

The driving force behind this addition was a new report published Nov. 19 by The London School of Economics and Political Science (LSE), which reviewed evidence from hundreds of scientific studies on these two invertebrate animal groups. 

Related: 8 crazy facts about octopuses

"After reviewing over 300 scientific studies, we concluded that cephalopod molluscs and decapod crustaceans should be regarded as sentient, and should therefore be included within the scope of animal welfare law," lead researcher Jonathan Birch, a philosopher of biological sciences at LSE, said in a statement. "I'm pleased to see the government implementing a central recommendation of my team's report."

Historically, it has been hard to prove sentience in animals because it is difficult to define.

"Sentience is the capacity to have feelings, such as feelings of pain, pleasure, hunger, thirst, warmth, joy, comfort and excitement," the researchers wrote in the report. However, pain reception is now widely considered to be the central criterion policymakers consider when drafting new legislation on animal welfare, they added.

The new study focused on evidence for different forms of pain reception, such as the possession of pain receptors and specific brain regions associated with pain, as well as behavioral experiments that show that these animals make choices to avoid painful or stressful scenarios. 

Being recognized as sentient means that the welfare of cephalopods and decapod crustaceans will have to be considered in any future decision-making processes, according to the U.K. government. "The Animal Welfare Sentience Bill provides a crucial assurance that animal wellbeing is rightly considered when developing new laws," Lord Zac Goldsmith, the U.K.'s animal welfare minister, said in the statement. "The science is now clear that decapods and cephalopods can feel pain, and therefore, it is only right they are covered by this vital piece of legislation." 

However, the new listing will not affect existing legislation surrounding these animals. This means several questionable practices — such as selling animals to untrained handlers, transporting animals in ice-cold water and boiling animals live without stunning them and other extreme slaughter methods remain legal even for sentient animals. 

The researchers are now calling for these practices to be outlawed. 

Boiling lobsters alive without stunning them is already illegal in the U.S., Switzerland, Norway, Austria and New Zealand, according to IFLScience.

Originally published on Live Science.

Following a torrential summer downpour in northern Arizona, hundreds of bizarre, prehistoric-looking critters emerged from tiny eggs and began swimming around a temporary lake on the desert landscape, according to officials at Wupatki National Monument.

These tadpole-size creatures, called Triops "look like little mini-horseshoe crabs with three eyes," Lauren Carter, lead interpretation ranger at Wupatki National Monument, told Live Science. Their eggs can lie dormant for decades in the desert until enough rainfall falls to create lakes that provide real estate and time for the hatchlings to mature and lay eggs for the next generation, according to Central Michigan University.

Triops' appearances are so uncommon, that when tourists reported seeing them at a temporary, rain-filled lake within the monument's ceremonial ball court — a circular walled structure 105 feet (32 meters) across — the monument's staff weren't sure what to make of the critters.

Related: Photos: Ancient sea monster was one of largest arthropods 

Following a monsoon in late July, "We knew that there was water in the ball court, but we weren't expecting anything living in it," Carter said. "Then a visitor came up and said, 'Hey, you have tadpoles down in your ballcourt.'" 

At first, Carter wondered if toads, which live in underground burrows during the dry season, had emerged during the wet spell to lay eggs. To investigate, she went to the ballcourt, which was originally built by the Indigenous people at Wupatki. 

"I just scooped it up with my hand and looked at it and was like 'What is that?' I had no idea," Carter said. But then, she felt an inkling of familiarity; Carter had previously worked at Petrified Forest National Park in northeastern Arizona, and recalled reports of Triops there. "And then I had to look it up," she said.

Three-eyed crustacean

Triops — which is Greek for "three eyes" — are sometimes called "dinosaur shrimp" because of their long evolutionary history; the ancestors of these crustaceans evolved during the Devonian period (419 million to 359 million years ago), and their appearance has changed very little since then, according to Central Michigan University. (Of note, the dinosaurs didn't emerge until much later, during the Triassic period, which began about 252 million years ago.)

However, Triops aren't exactly the same as their ancestors, so they wouldn’t be considered "living fossils."

"I don't like the term 'living fossil' because it causes a misunderstanding with the public that they haven't changed at all," Carter said. "But they have changed, they have evolved. It's just that the outward appearance of them is very similar to what they were millions of years ago."

There are two genuses in the family Triopsidae — Triops and Lepidurus — that together include up to 12 species, Central Michigan University reported. The critters found at the Wupatki ball court could be Triops longicaudatus, a species found in short-lived freshwater ponds, known as vernal pools, in North, Central and South America, but a scientific analysis is needed to confirm it, Carter said.

After hatching, Triops can grow up to 1.5 inches (4 centimeters) long, with a shield-like carapace that looks like a miniature helmet, according to Central Michigan University. Their eyes make them look angry and wise at the same time — they have two large, black-rimmed compound eyes (like those of a dragonfly or bee) and a small ocellus, or simple eye, between them. Ocellus eyes are common among arthropods (a group that includes insects, crustaceans and arachnids), which are filled with simple photoreceptors that help these creatures detect light, according to the Amateur Entomologists' Society.

Related: Photos: Ancient shrimp-like critter was tiny but fierce

In this case, the Triops at Wupatki National Monument got lucky with a short but intense rainy spell. Usually, Wupatki gets around 9 inches (22.9 cm) of rain a year, Carter said. In 2020, Wupatki had its driest lowest monsoon summer on record, with just 4 inches (10.2 cm) of rain, Carter said. But in the last week and a half of July 2021, the region got a tumult of rain: nearly 5 inches (12.7 cm). 

During that time, the Triops' eggs hatched and, within hours, the little critters likely began filter feeding, according to a life cycle description at Central Michigan University. Like other crustaceans, they went through several molts before fully maturing in just over a week.

Triops males and females typically pair up to mate by sexual reproduction, but in times of scarcity, they have other means; these crustaceans are also hermaphrodites, meaning they have both male and female sex organs, and parthenogenetic, meaning females can produce offspring from unfertilized eggs, according to BioKids, a partnership between the University of Michigan School of Education, University of Michigan Museum of Zoology and the Detroit Public Schools.

Triops can live up to 90 days, but the pond at the ball court lasted just three to four weeks, Carter said. Almost immediately, local birds took notice, with ravens and common nighthawks swooping down into the water to gobble up the critters, she noted.

It's unknown how many Triops managed to lay eggs before the lake dried up. Rangers will have to wait for the next monsoon to find out.

Editor's note: This story was corrected at 2:22 p.m. EDT to note that Triops means "three eyes" in Greek, not Latin, as was previously stated. It was updated at 9:32 a.m. EDT Oct. 6 to clarify that the rainfall measurements were for Wupatki, not Flagstaff, Arizona.

Originally published on Live Science.

During the early Jurassic period, a squid-like creature was in the midst of devouring a crustacean, when it was interrupted by another marine beast, possibly a shark, that chomped into its squishy side and killed it, a new study finds.

The shark swam away, but the crustacean and the squid-like animal — a 10-armed and two-finned creature called a belemnite — sank to the bottom of the sea, where they fossilized together over the subsequent eras in what is now Germany.

The resulting 180 million-year-old fossil is "unique," one of about "10 specimens of belemnites with [well-preserved] soft tissues worldwide," study lead researcher Christian Klug, curator of the University of Zurich's Palaeontological Museum and a professor at its Palaeontological Institute, told Live Science in an email. 

The specimen also shows how predators sometimes become prey themselves. "Predators tend to be happy when they are eating, forgetting to pay good attention to their surroundings and potential danger," Klug said. "That might explain why the belemnite got caught, but there is no proof for that."

Related: Image gallery: Photos reveal prehistoric sea monster 

The fossil also inspired a new term: pabulite, from the Latin words "pabulum" and "lithos," which mean "food" and "stone," respectively. Palubite refers to meal "leftovers" that never enter the predator's digestive system and later fossilize — in this case, that leftover would be the belemnite, the researchers wrote in the study. 

A pabulite can "provide evidence for incomplete predation," which is likely what happened here, the researchers wrote in the study. In fact, it's possible that the shark purposefully targeted the belemnite's squishy parts, rather than its pointy hard tip, known as the rostrum. Vertebrate predators likely learned to avoid the hard-to-digest rostra, and as a result may have "bit off the soft parts, which were poorly protected," the researchers wrote in the study.

"Remarkable" specimen

Amataur fossil collector Dieter Weber discovered the specimen in 1970 in a small quarry near Holzmaden, a small village near Stuttgart in southwestern Germany. Study co-researcher Günter Schweigert, curator of Jurassic and Cretaceous invertebrates at the State Museum of Natural History Stuttgart (SMNS), saw the specimen in 2019 while visiting Weber's collection, and SMNS purchased it soon after. 

Researchers immediately got to work studying the specimen. The belemnite, they discovered, was the well-known species Passaloteuthis laevigata, whose fossilized remains have been found in Europe and Morocco in rocks dating to the Toarcian age (183 million to 174 million years ago). P. laevigata was a small creature, with a nearly 4-inch-long (9.3 centimeters) bullet-shaped rostrum; each of its 10 arms were up to 3.5 inches (9 cm) long and carried double rows of arm-hooks. These hooks, 400 in all, would have helped P. laevigata grip slippery prey, Klug said.

"In this individual, two arms were modified, bearing large hooks," Klug noted, "We guess that these were used for mating and possibly only males had them, while in females, all 10 arms were similar, but we have no proof for that yet."

Belemnites are now extinct, but fossils reveal that they had an internal shell surrounded by muscles and skin, Klug said. These strong horizontal swimmers actively preyed on sealife, including fish and crustaceans, and in turn were eaten by sharks and dolphin-like predators known as ichthyosaurs, he said.

So, it's no surprise that this belemnite was chomping on a crustacean from the genus Proeryon, which had a broad and flat lobster-like body and long, slender claws, Klug said. However, the Proeryon was poorly preserved, so "we think that these are remains of an old skin (a molt)," he wrote in the email. "Crayfish remove much of the calcium from the shell before they molt, because they later put it into the new skin."

Related: Release the kraken! Giant squid photos 

Cephalopods (a group that includes octopuses, squid and nautiluses) "do love to eat this old skin," Klug added. "Much of it is lying really between the arms of the belemnite, quite close to its mouth, so it is likely that the belemnite was actually feeding on it."

Although parts of the belemnite are well preserved, including its rostrum and arms, much of its body is missing. This is why "we must conclude that a larger predator ate most of the belemnite," Klug said. 

What ate the belemnite?

A prime candidate for the belemnite's "killer" is the early Jurassic shark Hybodus hauffianus. A previously described H. hauffianus fossil was stuffed with belemnite remains, including dozens of rostra.

That particular H. hauffianus "possibly ran into a swarm of belemnites and got too enthusiastic about it: It ate about 200 of them but forgot to bite off the rostra, thereby clogging its stomach, which eventually killed it," Klug said. 

Other suspects include large predatory fish, such as Pachycormus and Saurorhynchus, the marine crocodile Steneosaurus, and the ichthyosaur Stenopterygius, whose fossilized stomach remains contain belemnite mega-hooks, the researchers wrote in the study.

The study was published online April 29 in the Swiss Journal of Palaeontology.

Originally published on Live Science.

Coconut crabs, Earth's biggest land crabs, are internet famous from images in which they dwarf trash bins and tear birds limb from limb.

But when these crabs aren't devouring seabirds, they're chatting to each other in vibrating clicks, and scientists recently discovered that the crabs' weird clicking calls are unexpectedly diverse. 

In fact, their crabby chatter contains a range of signals that could represent complex levels of communication (for a crab, at least), according to a new study. 

Related: Photos: Ancient crab is the strangest you've ever seen

Weighing up to 9 lbs. (4 kilograms) and with a leg span of more than 3 feet (1 meter), coconut crabs (Birgus latro) are gargantuan crustaceans and the largest terrestrial invertebrates in the world. These cousins of hermit crabs once inhabited islands across the Indo-Pacific area, but people harvested coconut crabs to extinction in many of their former habitats, scientists wrote in the study, published in the December issue of the journal Zoology.

Previously, the researchers found that the crabs produced "tapping-like sounds," but they were unsure how and why the animals made those noises. For the new study, the scientists captured X-ray movies of the clicking crabs to uncover the source of their acoustic prowess; they also recorded digital audio of the crabs during interactions between males and females, to see if the clicking was linked to mating behavior.

In experiments, male and female coconut crabs clicked before, during and after mating — and the sounds that they made were different at each stage. X-rays revealed that the crabs were communicating by vibrating thin appendages known as scaphognathites, which draw air into the crabs' lungs. When the structures vibrate, they flutter against hard plates in the crabs' gill channels to generate a tapping sound. By changing the structure's vibration speed, the crabs could produce multiple sounds that varied in frequency and intervals, according to the study.

The only other crustacean that produces sound with its scaphognathites is the aquatic crayfish (Procambarus clarkii), and coconut crabs are now the only land crustaceans known to exhibit this behavior, the researchers reported.

Trash can titans?

Long before coconut crabs caught scientists' attention with their clicking, they were renowned for their girth. More than a decade ago, the internet audience was transfixed (and terrified) by a much-circulated photo of a truly monstrous coconut crab that appeared to be the size of a trash can. However, the scale in the photo was misleading, and the crab — though large — was probably not quite as big as it looked, biologist Michael Bok wrote in January 2010 on his blog Arthropoda.

An outdoor trash can (such as the one in the crab photo) typically measures about 4.25 feet (1.3 m) tall, which led viewers to think that the crab was about that length. But the bin in the photo is likely much smaller than average, making the crab look bigger by comparison, Bok explained.

Coconut crab from r/WTF

Even if coconut crabs aren't as long as a trash can, they're still formidable creatures with a pinch more powerful than that of any other crustacean — and even stronger than most animals' bites, Live Science previously reported.

In fact, researchers documented a coconut crab snatching a large seabird from its nest, breaking its wings and ripping it to pieces, Science Alert reported in 2016. Gruesome footage captured by Mark Laidre, an assistant professor in the Department of Biological Sciences at Dartmouth College in New Hampshire, showed a stealthy crab using its pincers to cripple and subdue a red-footed booby (Sula sula) in the Chagos Archipelago in the Indian Ocean.

Though the experiments in the new study only recorded interactions between amorous male and female crabs, their clicking conversation could extend beyond mating encounters, the scientists wrote. However, more tests will be necessary under a variety of conditions in order to decode the extent of coconut crabs' "language," according to the study.

• In images: The amazing world of Antarctic yeti crabs
• Image gallery: Tiny crustaceans found in fossil reef
• A gallery of creatures that molt

Originally published on Live Science.

It's no mystery why natural selection favors bluish-green lobsters: Individuals that live inconspicuously on the seafloor are more likely to survive and pass their genes on to offspring.

Lobsters live in rocky or muddy areas, said Anita Kim, an assistant scientist at the New England Aquarium in Boston. They rely on a specialized blue pigment to blend into their environment and avoid the gaze of cod, haddock and other fish that enjoy lobster dinners.

However, as any lobster connoisseur knows, these crustaceans turn bright red when they're heated. So, why does this dramatic color transformation happen? [Do Lobsters Live Forever?]

Scientists have struggled to understand this pigment change since the 1870s. Well over a century passed before the biochemistry came into focus. As it turns out, lobster camouflage is the product of two molecules: a protein called crustacyanin and a carotenoid (a pigment responsible for bright red, yellow and orange hues) called astaxanthin.

Lobsters can't make their own astaxanthin, so they get it from their diet.

"It's very similar to beta-carotene," Kim told Live Science. "Flamingos eat shrimp with beta-carotene and turn pink. When a lobster eats astaxanthin, it gets absorbed into their body."

But that isn't a simple process. Astaxanthin is red, but it turns live lobsters bluish green. It wasn't until 2002 that researchers discovered that the protein crustacyanin changes the color of the pigment astaxanthin by twisting the molecule and changing how it reflects light.


"When astaxanthin is free, it's red. When it's bound to crustacyanin, it turns blue," Michele Cianci, a biochemist at Marche Polytechnic University in Italy, told Live Science. He was a doctoral student in the lab where researchers discovered the phenomenon.

Into the pot

When lobsters are heated to high temperatures — whether they're boiled, baked or grilled — crustacyanin lets go of astaxanthin, allowing the pigment to untwist and show its true color.

As the lobster is heated, the crustacyanin molecules lose their shape and reorganize in different ways, Cianci said. This physical change in the protein's shape has a noticeable effect on the lobster's color.

To put it another way, "imagine holding a rubber band in your hands," Cianci said. "You can impose any kind of configuration you want," just as the crustacyanin molecules can twist the astaxanthin.

"When you release the rubber band, it goes back to its own shape," he said. Likewise, when the crustacyanin is heated, it lets go of astaxanthin, allowing the pigment to turn red again.

Scientists have nailed down the chemistry, but they still don't completely understand the physics of how crustacyanin can temporarily and reversibly make a red pigment blue. Several research groups are using a range of techniques to figure out how crustacyanin and astaxanthin work together to reflect blue light.

"Why astaxanthin is blue when it's bound is being investigated," Cianci said. But that shouldn't stop you from dropping some knowledge about carotenoids with your friends next time you chow down on a succulent red lobster.

• What Happens to a Dead Body in the Ocean?
• Why Is the Ocean Blue?
• Why Do Seashells Sound Like the Ocean?

Originally published on Live Science.

An international team of astronauts has discovered a new species of blind, colorless, cave-dwelling crustacean — and they didn't even have to leave Earth to find it.

The fingernail-size crustacean, named Alpioniscus sideralis after the Latin word for "stellar," was discovered scuttling about a pitch-black pool in the Sa Grutta cave system below Sardinia, Italy. Fledgling astronauts discovered the tiny cave-dweller while spending six nights belowground as part of the European Space Agency's CAVES training program, which encourages International Space Station candidates to conduct research together in perilous subterranean environments.

During a 2012 expedition underground, astronaut trainees from Europe, the United States, Russia, Canada, Japan and China encountered the tiny, translucent crustaceans in a small cave pond. The astronauts lured the creatures out of the water using a bait of liver and rotten cheese, then transported the specimens back to the surface. [In Images: Creepy, Crawly Cave Creatures]

Molecular analysis showed that A. sideralis' genetics didn't match that of any other species collected from the region, allowing the intrepid astronauts to describe it for the first time in a new study published December 2018 in the journal ZooKeys.

A. sideralis was revealed to be a type of woodlice — tiny crustaceans that left the water to colonize land millions of years ago. Remarkably, A. sideralis seems to have done an evolutionary about-face, turning its armored back on the land and returning to subterranean waters like the cave pools of Sardinia.

"I would like to think that when humans land on Mars and explore its caves, this experience will help them to look for other species, knowing that life has few limits and can develop in the most inhospitable places," Paolo Marcia, a zoologist from the University of Sassari and co-author of the study, said in a statement.

• Photos: The Creatures That Call Lava-Tube Caves Their Home
• Amazing Caves: Pictures of Earth's Innards
• The 7 Longest Caves in The World

Originally published on Live Science.

Certain giant, herbivorous dinosaurs didn't eat just plants — they also chowed down on rotten logs harboring shellfish, a new study finds.

Researchers made this startling dietary discovery after examining 10 different specimens of fossilized dinosaur dung, known as coprolites, from the Kaiparowits Formation of Grand Staircase-Escalante National Monument in southern Utah.

"If we had found just one coprolite with crustacean pieces in it, that would have been interesting," said study lead researcher Karen Chin, an associate professor and a curator of paleontology at the University of Colorado Boulder. "But the fact that we found coprolites that spread out over at least 20 kilometers [12 miles] at different stratigraphic levels — that really strengthens our evidence for this being a behavior that these dinosaurs engaged in." [Image Gallery: Parasite Eggs Lurk in Fossilized Shark Poop]

The coprolites with the crustacean shells — including what might be a crab shell — are filled with the remains of rotted wood, and date to between 76 million and 74 million years ago. Rotten wood is "kind of an unusual diet," Chin said, "but when you rot the wood, it increases the availability of cellulose [fiber] in the wood. Ranchers down in Chile have been known to open up rotted logs and their cattle just gravitate toward them and start feeding on the rotted wood."

It's possible that the dinosaurs ate the rotted wood to get fiber, as well as fungus and insects living in the rotted logs, Chin said. Of course, by eating the logs, the dinosaurs were also swallowing the crustaceans living in the damp, decomposing logs, but it's unclear whether the dinosaurs were purposefully or unintentionally eating the crustaceans, Chin said.

However, given that crustaceans are a good source of protein and calcium — a mineral needed during eggshell production — perhaps female dinosaurs were intentionally eating the crustaceans in preparation for laying eggs, a behavior also seen in breeding birds, Chin said.

It's unclear what type of Late Cretaceous dinosaur left the poop, but the formation was filled with the fossils of duck-billed dinosaurs, or hadrosaurs. Those dinosaurs' duck bills had teeth that were powerful enough to grind rotted logs, and so the droppings likely came from Gryposaurus, a 27-foot-long (8 meters) duck-billed dinosaur found at the site, Chin said.

What's more, the researchers wanted to make sure that the thick crustaceans were digested, as opposed to wandering into the dinosaur feces after the fact. But the evidence is fairly clear that the dinosaurs ingested the critters, Chin said.

"If the crustacean had just wandered in there, even if it had been stepped on by a dinosaur, it would mostly be together," Chin said. "These pieces of crab are scattered throughout the coprolites."

Chin noted that this is the first example on record of "fairly large" crustacean fragments in dinosaur coprolites. There are dinosaur coprolites from India containing teeny, tiny ostracods — crustaceans also known as seed shrimp — but these ostracods are just 0.04 inches to 0.08 inches (1 to 2 millimeters) long, while the fragments from this study are as large as 1.1 inches (3 centimeters) across, Chin said.

The study "kind of turns our stereotype of plant-eating dinosaurs on its head," said Steve Brusatte, a paleontologist at the University of Edinburgh in Scotland who was not involved in the research.

"When you cut into the coprolite of a plant-eating dinosaur, you expect to find only plants, so the crustaceans inside are a real surprise," Brusatte said.

Still, despite its shock value, the finding is not too unexpected, Brusatte said. "A lot of herbivores today also ingest animals, sometimes accidentally or sometimes to supplement their diet. These dinosaurs were no different."

The study was published online today (Sept. 21) in the journal Scientific Reports.

Original article on Live Science.

Between their hard shells and strong pincers, American lobsters are built to fight and keep other creatures away. But does this combative, standoffish nature extend to mating?

There are two general groups of animals called lobsters: clawed lobsters, which live in high-latitude, cold-water regions; and spiny lobsters, which are clawless and live in warmer sub-tropical waters. Clawed lobsters and spiny lobsters are not closely related.

Clawed lobsters, including the American (Maine) and European lobsters, typically live in small, hierarchical groups, said biologist Jelle Atema, who studies American lobsters at Boston University and the Woods Hole Oceanographic Institution. Males vigorously fight each other to be the dominant male of the group, though it’s a short-lived title given that lobsters remember whom they've fought for no longer than a week.

For the most part, these contests establish which crustacean gets the best shelter — something also important for females. "Females fight just as much as males," Atema told Live Science. "We think they have a dominance hierarchy, as well."

The soap opera

Female lobsters will usually mate only after they molt, which typically occurs during the warm, summer months, particularly the middle of June. If a female were to mate with her hard shell on and then molt sometime afterward, she may lose stored sperm, which she keeps in a receptacle at the bottom of her thorax, or she could even lose fertilized eggs, which she holds underneath her tail. 

How often a female will molt — and be receptive to mating — depends on her size, with the smallest of mature females molting every year and the largest every several years, Atema said.

As the female nears molting time, she will search for a suitable partner. While sitting in their rock shelters, males will use the swimmerets (appendages resembling small fins) under their abdomens to create powerful currents that shoot out into the environment. These currents are loaded with chemical cues that attract females looking to mate.

Females appear to know who is the dominant male in a group, possibly by his odor or physical size, Atema said. If a female impatiently decides to go into the shelter of a subordinate male (because the dominant male is already shacked up with another female, for example), the dominant male may eventually come by and kick the subordinate male out of his home, possibly resulting in the female losing out on her mating chances or from being protected while she molts.

"It's sort of like a soap opera," Atema said.

Lobsters, by nature, are aggressive and territorial, but females have a crafty weapon up their shells: pheromones, which not only reduce male aggression but also reflexively close males' claws.

After wafting her pheromone-laced urine into the dominant male's shelter, the female will eventually work up the courage to enter his domain. In the male's shelter, the pair will playfully "box" or tap each other's claws, and then hang out peacefully until the female is ready to molt, possibly a few days later.

A tender affair

Mating among lobsters is a tender, human-like affair.

"When it's time to molt, the female does something very remarkable," Atema said. "She will go up to the male and place her claws on his so-called shoulders — next to the eyeballs on top of the carapace — and then take her claws back." This gentle act tells the male that she is ready to molt and mate.

The female will then lie on her side, shrink her soft body away from her exoskeletonshell, and then slip out of her shell, a process that takes about 15 minutes. Meanwhile, the male stands over her, touching her with his antennae and smelling her.

Once "undressed," the female will lie down right-side up with her abdomen and claws stretched out. The male will carefully begin to mount her and, using his walking legs and mouth parts, will turn the female over so that she is splayed out on her back. He'll then insert his first pair of spinnerets into the female's seminal receptacle cavity for a few second to pass his sperm to her.

After mating, the female will absorb water to grow in size and prepare for her new, larger shell to harden over. She'll spend the next week or so in the male's den while her shell hardens. Once armored, the female leaves the male's home, making way for another female to take her turn.

Many months later, the female will push thousands of eggs out of her ovaries and through the sperm receptacle, where they're fertilized. She'll carry these eggs, glued to the bottom of her tail, for the next 9 to 11 months.

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The vast underwater wilderness of the deep sea may be largely unexplored by humans, but it's still incredibly polluted, a new study finds.

Researchers made the finding by using baited traps to capture tiny crustaceans in the Mariana Trench in the western Pacific Ocean — the deepest known spot on Earth — and the Kermadec Trench, which sits off the northeastern coast of New Zealand.

Surprisingly, pollution concentrations in the crustaceans plucked from the Mariana Trench were 50 times higher than those in crabs found in paddy fields fed by the Liaohe River, one of the most polluted rivers in China, the researchers wrote in the study. [In Photos: World's Most Polluted Places]

"The only Northwest Pacific [Ocean] location with values comparable to the Mariana Trench is Suruga Bay (Japan), a highly industrialized area," the researchers wrote in the study.

Humans know more about the surface of the moon than they do about the ocean floor. To learn more, the scientific team studied the hadal zone, "the last major marine ecological frontier," which encompasses the area 3.7 miles to 6.8 miles (6 kilometers to 11 km) under the water's surface, the researchers said.

The hadal zone includes deep-sea trenches. People usually assume that deep-sea trenches are pristine, but in reality, these trenches are the dustbins of the ocean, collecting debris as it slowly sinks to the ocean floor, the researchers said.

To get a better idea of the pollutants there, the researchers set baited traps for teeny crustaceans, called amphipods, that live and scavenge in deep-sea trenches. The scientists analyzed the amphipods' fatty tissues for levels of persistent organic pollutants (POPs), which can disrupt hormones in living beings.

POPs can enter the environment through industrial accidents and discharges, leakage from landfills or incomplete incineration, the researchers said. Two POPs of great concern are polychlorinated biphenyls (PCBs, used as dielectric fluid) and polybrominated diphenyl ethers (PBDEs, used as flame retardants), according to the scientists.  

"The salient finding was that PCBs and PBDEs were present in all samples across all species at all depths in both trenches," the researchers wrote in the study.

The amphipods in the Mariana Trench had higher PCB levels than did the amphipods in the Kermadec Trench, but it's unclear why. One idea is that the Mariana PCBs come from the nearby North Pacific Subtropical Gyre — more commonly known as the Great Pacific Garbage Patch — the researchers said. The patch is about the size of Texas, and formed when millions upon millions of plastic and garbage fragments got trapped in a vortex between ocean currents, Live Science reported previously.

The results show that human-caused contamination can be found at the far reaches of the Earth, even in the Mariana Trench, which is deeper than Mount Everest is tall, the researchers said.

The findings are "disturbing," said Katherine Dafforn, a senior research associate in the School of Biological, Earth and Environmental Sciences at the University of New South Wales in Australia. Dafforn was not involved in the new study but wrote an accompanying editorial about it.

"This is significant since the hadal trenches are many miles away from any industrial source," Dafforn wrote in the opinion piece. "[It] suggests that the delivery of these pollutants occurs over long distances despite regulation since the 1970s."

Both the study and the editorial were published online Monday (Feb. 13) in the journal Nature Ecology & Evolution.

Original article on Live Science.

What makes a female marine crustacean "swipe right" on a prospective mate? If she's Dulichiella appendiculata — a tiny relative of the sand-hopping beach flea — she's impressed by the size of the male's enlarged right front claw, which is significantly bigger than its left one.

And she definitely prefers righties to lefties.

Scientists have investigated the mating success of right-clawed D. appendiculata males versus their left-clawed rivals, and found that righty males attracted more females. But lefties were found to be more solitary than righties, with a tendency to disperse into more habitats. And moving into a territory where there's less competition increased their chances of finding a willing female, the scientists found. [In Images: The Menagerie of Tiny Alienlike Creatures Under the Sea]

Study lead author Pablo Munguia, an ecologist and evolutionary biologist at the University of Adelaide's School of Biological Sciences, told Live Science in an email that he "bumped into" this heavy-handed species while studying reef diversity in Florida for his doctoral dissertation. Munguia was captivated by the peculiar asymmetrical claws, which were present only in males. But it wasn't until more than a year later that he realized that there were "righties" and "lefties" in D. appendiculata populations, and that this might be linked to mating prowess.

Looking for a right-hand man

D. appendiculata is a type of amphipod — a flattened and shell-less crustacean — that lives on reefs or hard structures like shells, and measures about 0.2 to 0.24 inches (5 to 6 millimeters) in length.

And in relation to its body size, one of the male's two claws is enormous.

"The claw can be 2 to 3 millimeters (0.08 to 0.12 inches) long," Munguia told Live Science. "To put it in perspective, it is 20 to 30 percent of the length of the adult male," he said. This kind of dramatic asymmetry is rare in animals, the study authors reported.

The claws grow as the male matures, Munguia said. Juveniles are miniature versions of the adult forms, and their bodies — and the males' claws — get bigger with every molt. In addition, the claw takes on its distinctive ax-like shape over time. It's not yet known at what age D. appendiculata becomes sexually mature, though Munguia said that other closely related species reach sexual maturity about a month after hatching.

"When males reach approximately 3 millimeters [in length], one can tell whether the individual is becoming a righty or a lefty," Munguia said.

Males use their enlarged claw not only to attract females, but also to guard their mates from other males.

The right stuff

To study these tiny creatures, Munguia spent three summers collecting and analyzing hundreds of individuals living inside pen shells, which were vacant of their usual mollusk inhabitants, in Florida seagrass beds. The researchers discovered that there were approximately the same number of righty and lefty males in the overall populations.

But wherever there was an abundance of D. appendiculata, most of the males were right-clawed, Munguia told Live Science. The right-clawed males tended to congregate around females — and each other — more than the left-clawed males, which were quicker to seek out new habitats where competition would be lower.

Females preferred males with an enlarged right claw, but in habitats where populations were sparse, lefties dominated, and were more likely to find a mate than if they were living in more crowded spots.

"The two alternative modes of gaining access to females seem to have found a balance," Munguia wrote in the email. Further studies will determine the stability of this balance between righties and lefties in D. appendiculata and in related amphipod populations in other marine habitats, he added.

The findings were published online May 31 in the Journal of Crustacean Biology.

Original article on Live Science.

A mysterious 160-million-year-old crustacean had incredibly complex eyes similar to those of modern arthropods, a group that includes insects and other crustaceans, among other animals, a new study finds.

The ancient marine arthropod, known as Dollocaris ingens, likely used its exceptional vision to hunt, possibly as an ambush predator, the researchers said.

"It's a very weird creature, indeed," said study lead researcher Jean Vannier, a paleobiologist at the French National Center for Scientific Research in Lyon. "We found the remains of undigested shrimps in its stomach, and the animal had obvious [grasping] legs. No doubt, acute vision was essential in its daily life." [Fabulous Fossils: Gallery of Earliest Animal Organs]

Typically, Vannier studies creatures that lived during the Cambrian period (between 541 million and 485.4 million years ago), when many animal groups first appeared in the fossil record. Complex sight also evolved during this time, and was a real game changer for these organisms.

"When vision appeared, things changed dramatically," Vannier told Live Science. "Animals with eyes could detect prey more easily, and prey had to worry about it."

But scientists have yet to find a well-preserved eye with fossilized sensory cells from the Cambrian period, he said. So, Vannier and his colleagues turned to the D. ingens fossils dating back 160 million years, to the Jurassic period. The fossils were discovered in the 1980s in the La Voulte-sur-Rhone formation in southeast France, but they had not been properly studied until now, he said.

The eyes of D. ingens are a remarkable find, Vannier said. "Such exceptional preservation of an eye had never been observed in the fossil record, except in very recent fossil flies in amber," he said.

Super Surpr-eyes

D. ingens belongs to an enigmatic extinct group of crustaceans called thylacocephalans, which don't resemble any modern crustaceans, Vannier said. He and his colleagues discovered its incredibly preserved eyes while examining the critter, which measures between 2 and 8 inches (5 and 20 centimeters) in length.

To study the creature's internal organs, they used X-ray microtomography, a technique that compiles X-ray cross-section scans to make a virtual 3D model. Then, they used a scanning electron microscope, which helped them discover the exceptional eyes.

The eyes make up nearly one-fourth of the animal's entire body, and each eye has about 18,000 ommatidia, tiny cylinders that make up a compound eye (think of a fly's eye). D. ingens has more of these cylinders, which contain a lens and light-receiving sensory cells, than any other modern arthropod except the dragonfly, which has about 30,000.

The size, shape and number of these ommatidia indicate that D. ingens had "acute vision, which normally characterizes predators" such as dragonflies and mantis shrimps, Vannier said.

The study was published online Tuesday (Jan. 19) in the journal Nature Communications.

Follow Laura Geggel on Twitter @LauraGeggel. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

The mystery of the origin of two strange-looking species of "vampire crabs" is finally solved. The crabs come from the island of Java in Indonesia, according to the scientists who officially describe the species in a new report.

Vampire crabs owe their name to their spooky appearance, as they have bright-yellow eyes contrasting sharply with purple or orange abdomens.

People in the aquarium trade have known of the two crab species described in the report for at least a decade, said Peter Ng, a biology professor at the National University of Singapore and an author of the report. Ng said he saw the crabs for the first time in aquaria in Singapore, where the crustaceans were being sold as pets.

The problem for scientists was that it was not clear where the crabs originally came from, which made it difficult for researchers to actually name and describe the traits of the species in the wild. [The 7 Weirdest Glow-in-the-Dark Creatures]

"For a species to be formally and properly described and named, its provenance should be known," Ng told Live Science. "Of course, it is perfectly legal to name a species without knowing where it comes from, but that would be bad science and irresponsible."

Crab dealers have pointed to a number of possible places of origin for the crabs, from Java to Krakatoa, Borneo, Sulawesi and even New Guinea. But all of those sites were suspicious, Ng said.

With a good deal of detective work, study coauthor Christian Lukhaup, a German carcinologist (crab expert), traced the crabs' origins from dealers in Germany all the way back to Java, Ng said. Lukhaup persuaded businessmen and traders to connect him to the people in Java who were actually collecting the crab. These collectors then passed specimens of the animals on to the researchers.

The two new species have been named Geosesarma dennerle and Geosesarma hagen. There are now 53 species of Geosesarma genus known to science, said Ng, who himself has named 20 of the species. He said he currently has another half a dozen or so newly collected Geosesarma species from Southeast Asia in his lab, and these species still need to be named and described.

"So there are more to come as we explore and discover them," he said.

But the two newly described species may already be under threat from potential over-collecting for the aquarium trade, the researchers said. "Any species that is over-exploited — be it for food, or as a pet — stands [to be] threatened," Ng said. "More so for a small freshwater crab like this, which has a relatively restricted range."

The researchers said they are also worried about "the potential loss of [the crabs'] pristine habitat," Ng said. If this habitat becomes polluted or changed by human activity, the crabs' populations may collapse, he said.

"The nightmare for biodiversity researchers is that we are always working against the clock — too many species to discover and too little time," Ng added.

The study was published online Jan. 16 in the journal Raffles Bulletin of Zoology.

Follow Agata Blaszczak-Boxe on Twitter. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

It's not every day that an ordinary fishing trip turns into an encounter with an oversized alien-like sea creature, but that's what happened recently to one Florida fisherman.

Steve Bargeron was fishing off a dock in Fort Pierce, Florida, last week when a couple fishing nearby pulled up what Bargeron jokingly described as an "alien creature." The couple wasn't interested in keeping the strange, lobster-like animal, which was flopping its tail wildly, Bargeron told Live Science. So the curious fisherman took a few photos and then threw the critter back into the water.

But Bargeron's close encounter with this strange-looking specimen isn't really that strange after all, according to Roy Caldwell, a professor of integrative biology at the University of California, Berkeley. Caldwell said he saw the photos online and instantly recognized the creature as a mantis shrimp, or stomatopod, a marine crustacean commonly found in the waters off Florida. [See Photos of the Alien-Like Shrimp Caught Off Florida]

Stomatopods are easily identified by their prominent claws, which, depending on the species, they use to either stab or smash prey, Caldwell said.

"Praying mantis have similar [appendages], which is why these creatures are sometimes called 'mantis shrimp,'" Caldwell told Live Science.

The specimen caught in Florida belongs to a species of Lysiosquilla, according to Caldwell. Like other members of its species, the creature has three pairs of walking legs and a large, articulated abdomen, Caldwell noted.

"This particular group — Lysiosquillidae — are almost all banded yellow and black across their bodies," Caldwell said. They can live for 30 years and can grow to be 12 inches (30.5 centimeters) long, he added.

But this specimen doesn't belong to the largest of stomatopod species, according to the biologist. That distinction goes to Lysiosquillina maculata, which inhabit the Pacific Ocean from Hawaii to east Africa. Caldwell said the largest known members of the species were 15 inches (38 cm) long.

Even so, Bargeron said the mantis shrimp he found recently was significantly bigger than the largest-known Lysiosquillina maculata at 18 inches (46 cm) long. However, the fisherman pointed out that he didn't have a tape measure handy to properly record the size of the catch.

Caldwell, who said he's been studying stomatopods for 50 years, said an 18-inch catch is unlikely. Photos, he pointed out, can sometimes be deceiving. He also noted that, with its claws extended, a stomatopod tends to look much longer than it really is. The standard for measuring the creatures is from the tip of the eye to the end of the tail — claws not included.

But the sighting of a mantis shrimp is still something to celebrate. Fishermen and other water-loving folks don't often get to see these strange-looking animals, because they live in burrows on the seafloor and seldom come out. In fact, female mantis shrimp may never leave their burrows during their lifetime, Caldwell said.

Follow Elizabeth Palermo @techEpalermo. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

The oldest fossil evidence of animal "babysitting" now comes from 450-million-year-old rocks in New York.

Small marine animals called ostracods, a group of crustaceans that includes more than 20,000 species living today, were discovered buried with their eggs and young by a team led by researchers from the University of Leicester in Britain. The findings were published today (March 13) in the journal Current Biology.

"This is a very rare and exciting find from the fossil record," David Siveter, lead study author and a geologist at the University of Leicester, said in a statement. "Only a handful of examples are known where eggs are fossilized and associated with the parent. This discovery tells us that these ancient, tiny marine crustaceans took particular care of their brood in exactly the same way as their living relatives."

The ostracod specimens are among the rare fossils that preserve body tissues, such as limbs, embryos and other soft parts. These tissues have been replaced by the mineral pyrite, or fool's gold, but the mineralization means the researchers could closely examine the tiny fossils by X-ray and CT scanning.

The tiny fossils, each less than a quarter-inch (2 to 3 millimeters) long, were collected from a rock layer called the Lorraine Group. Composed of muddy seafloor sediments, the layers have also yielded other spectacular sea creatures from the Ordovician Period, such as spiky trilobites. Researchers have uncovered older evidence of egg laying by animals, such as 600-million-year-old fossil embryos from rocks in South China, but this is the first time that brooding has been discovered so far back in invertebrates.

The newly discovered species reported in the study was named Luprisca incuba after Lucina, the Roman goddess of childbirth. The fossils are now part of the collection at the Yale Peabody Museum of Natural History, the researchers said.

Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Crazy Eyes

The peacock mantis shrimp, like this juvenile Odontodactylus scyllarus, are smashing superheroes. The colorful crustaceans have a hammerlike claw that can smash prey with the acceleration of a 0.22-caliber bullet — not unlike Thor's mythological weapon. Turns out, they also have super vision, sporting 12 different types of photoreceptors when four to seven are all that is needed.

Purple-Spotted Mantis

Researchers reporting in the Jan. 24, 2014, issue of the journal Science figure out the mantis shrimp's unique color vision system. Despite the baffling number of photoreceptors, the creatures, like this purple-spotted mantis (Gonodactylus smithii), couldn't easily discriminate between similar colors in a lab experiment.

Baby Peacock Mantis

To account for this seeming lack of superb color vision, researchers suggest mantis shrimp (juvenile peacock mantis shown here) each of their 12 photoreceptors is set to a different sensitivity. That way they can scan objects with all photoreceptors without the need for complex neural processing.

Shrimpy Vision

Unlike human eyes, which are equipped with three types of photoreceptors that send signals to the brain for comparison, mantis shrimp eyes create a pattern that is recognized as a color almost immediately, the researchers find. As such, mantis shrimp like this juvenile peacock mantis, shown here, lose some of their ability to discriminate between colors; even though they may not be able to tell the difference between light orange and dark yellow, for instance, they would easily detect basic colors without having to making comparisons between wavelengths of light in their brain.

Dinner?

Here, a mantis shrimp (Lysiosquillina sulcata) looks at a damselfish (Chrysiptera cyan.).

Near Miss

The mantis shrimp Lysiosquillina sulcata just misses the damselfish Pomacentrus coelestis.

Got It

Score! The mantis shrimp Lysiosquillina sulcata catches the damselfish Dascyllus melanurus.

Googly Eyes

The Odontodactylus cultrifer mantis shrimp shows off its amazing eyes. The unique color vision saves the mantis shrimp energy, which they need in the combative world of coral reefs where they live, say researchers.

More Peepers

Here, the eyes of the mantis shrimp Pseudosquillana richeri.

Shrimp Eyes

Another look at the eyes of the mantis shrimp Pseudosquillana richeri.

Japonicus Eyes

The eyes of the mantis shrimp Odontodactylus japonicus.

Animal Vision

The eyes of the mantis shrimp Raoulserenea hieroglyphica.

Mantis Shrimp

The eyes of the mantis shrimp Raoulserenea komai.

Training a Shrimp

The mantis shrimp Haptosquilla trispinosa. When researchers trained H. trispinosa to associate a spectral light with a food reward, it could discriminate wavelength differences of about 25 nanometers, or about the difference between what we see as pure yellow and orange. For comparison, humans can distinguish wavelength differences of 1 to 4 nm.

This Research in Action article was provided to LiveScience in partnership with the National Science Foundation.

In July 2012, marine biologist Paul Sikkel of Arkansas State University announced he had discovered a new coral reef crustacean, which he had named Gnathia marleyi, after the late Jamaican reggae artist Bob Marley. The news kicked off a media storm — drawing worldwide coverage from outlets including CBS News, the Associated Press, Reuters, CNN, Fox News, NPR, the BBC and AFP. The story generated so much public interest (a rarity for taxonomy news), that it spawned a question on Jeopardy. Even People magazine named the discovery one of 2012's most intriguing things.

Most of the coverage was, to Sikkel's delight, positive. After all, Sikkel had named the "true natural wonder" for Marley because of his respect and admiration for Marley's music. Plus, he says, "Gnathia marleyi is as uniquely Caribbean as was Marley."

Parasites warrant our awe and deference, says Sikkel. They are among the most successful creatures on Earth — "biological champions" vital to coral reef ecology. In fact, parasites account for the majority of inhabitants of coral reefs, which are the world's most diverse ecosystems.

But, proving that beauty is in the mind of the beholder, some Marley fans objected to the association between Marley and his marine namesake. Why? Biological wonder though it may be, Gnathia marleyi is also a blood-sucking parasite. To detractors, this suggests a gamut of unflattering connotations.

The controversy over Gnathia marleyi has provided Sikkel with eye-opening perspectives. In the videos below, Sikkel talks with Amlak Tafari, the bassist for the Grammy-winning reggae band Steel Pulse and a self-described amBASSador, about naming Gnathia marleyi after Marley, the resulting controversy, the ecological importance of coral reefs and how both men are using the arts to educate people about scientific issues, including coral reef ecology.

More information:

• An NSF article and interview about how species are named is here.
• A profile of Sikkel is here.
• An article about Sikkel's research on the importance of parasites to coral reefs is here.
• An article about Sikkel's lively, creative teaching style (which incorporates Jimmy Buffet music) is here.
• Paul Sikkel's website is here.

Editor's Note: Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. See the Research in Action archive.

Scientists have long held that crabs are unable to feel pain because they lack the biology to do so, but behavioral evidence has recently shown otherwise. Now, new research further supports the hypothesis that crabs feel pain by showing that crabs given a mild shock will take steps to avoid getting shocked in the future.

From humans to fruit flies, numerous species come equipped with nociception, a type of reflex that helps avoid immediate tissue damage. On the other hand, pain, which results in a swift change of behavior to avoid future damage, isn't so widespread. (Research has also shown naked mole rats may be immune to pain.)

In the new study, researchers allowed shore crabs (Carcinus maenas) to choose between one of two dark shelters in a brightly lit tank. One shelter came with a mild shock. After just two trials, crabs that initially chose the shocking shelter began opting for the zapless shelter, suggesting they learned to discriminate between the two options and headed for the less painful one.

"It's almost impossible to prove an animal feels pain, but there are criteria you can look at," said lead researcher Robert Elwood, an animal behaviorist at Queen's University, Belfast, in the U.K. "Here we have another criteria satisfied — if the data are consistent, a body of evidence [showing crabs feel pain] can build up."

Building evidence

Elwood initially set out to see if crabs and other crustacean decapods feel pain after a chef posed him the question around eight years ago. If the invertebrates (animals without backbones) feel pain, he reasoned, their reactions to unpleasant stimuli would be more than the simple reflex of nociception — the experience would change their long-term behavior.

Elwood's first experiment showed that prawns whose antennae were doused with caustic soda vigorously groomed their antennae, as if trying to ameliorate pain. Importantly, this behavior didn't occur if Elwood treated the antennae with an anesthetic first.

Another experiment showed that hermit crabs would leave their shells if given a mild shock. "A naked crab is basically a dead crab — they were trading off avoiding the shock with getting out of the shell," Elwood told LiveScience, adding that many of the crabs moved into new shells if any were available. [The 10 Weirdest Animal Discoveries]

For his new study, Elwood tested 90 shore crabs, which naturally seek dark spaces, to see if they exhibited "avoidance learning" and would discriminate between a dangerous and a safe area. Half of the crabs were shocked upon entering the first chamber of their choice, while the other half were not. For each crab, the jolting chamber stayed the same throughout the 10 trials.

In the second trial, most of the crabs returned to their original shelter; whether they were shocked in the first trial had little effect on their second choice. However, crabs were more likely to change shelter in the third trial if they were shocked in the second trial. And as the trials wore on, crabs that chose incorrectly became more likely to exit the unpleasant chamber, brave the bright arena and hide in the alternate shelter. By the final test, the majority of the crabs chose the nonshock shelter at first go.

Time for change?

The research "provides evidence that supports the issue that crabs — and other crustacean decapods as well — feel pain," Francesca Gherardi, an evolutionary biologist at the University of Florence in Italy who wasn't involved in the study, told LiveScience in an email. "It is avoidance learning that makes the difference."

Animals in pain should quickly learn to avoid the unpleasant stimulus and show long-term changes in behavior, Gherardi noted. More research is needed on decapods' avoidance learning and "discrimination abilities between painful and nonpainful situations," he said.

Elwood said he thinks future research should go in a different direction. Stress often comes with pain, he said, so other experiments could look at changes in crustacean hormones or heart rates due to shock.

Whatever the case, Elwood feels it may be time to reconsider the treatment of decapods in the food industry. "If the evidence for pain in decapods continues to stack up with mammals and birds that already get some protection, then perhaps there should be some nod in that direction for these animals," he said.

The study was published today (Jan. 16) in the Journal of Experimental Biology.

Follow LiveScience on Twitter @livescience. We're also on Facebook &Google+.

Mantis Shrimp

The colorful mantis shrimp Gonodactylus smithii. Researchers compare mantis shrimp to "heavily armored caterpillars."

Peacock Mantis Shrimp

The peacock mantis shrimp Odontodactylus scyllarus from the Indo-Pacific boasts strong, hammer-like claws.

Peacock Mantis

Peacock mantis shrimp are solitary hunters, capable of swinging their claws with a force equal to a .22 caliber bullet.

Mantis Shrimp with Eggs

A mantis shrimp guards a raft of pink eggs.

Green Shrimp

Peacock mantis shrimp are known for their complex visual system.

Territorial Crustacean

Peacock mantis shrimp are highly territorial.

Armored Crustacean

A view of the colorful peacock mantis shrimp body.

Smashing Close-Up

Peacock mantis shrimp are not shrimp, but their shrimp-like appearance (and tendency to attack like a praying mantis) gave them their name.

Molting Daphnia Magna

A water flea (Daphnia magna) undergoes molting. Like all crustaceans, this tiny creature must molt to grow.

Water Flea

A water flea, part of the order Cladocera, is a small crustacean only a few millimeters long.

C. elegans

Caenorhabditis elegans, a nematode worm and one of the most-studied organisms in the lab. C. elegans moves through four larval stages, molting after each one.

Wall Lizard

Like other lizards, the common wall lizard sheds its skin when it outgrows it.

Panther Chameleon

As this panther chameleon grows, it will slough off its old skin to reveal new skin beneath.

Mexican Red-Kneed Tarantula

Tarantulas (and other spiders) must molt as they outgrow their exoskeletons. Freshly molted spiders are very soft and vulnerable until their new exoskeletons harden.

Mangrove Tree Crab

Crustaceans like this mangrove tree crab also molt to grow.

Common Garter Snake

It's no secret that snakes shed their skin. Here, a common garter snake mugs for the camera.

Carolina Anole

Another lizard molter, the Carolina Anole.

Amazon Milk Frogs

Amphibians, including these Amazon Milk Frogs, molt periodically. Many frog species eat the shed skin.

Agile Frog

An agile frog perches on a leaf. Frogs can molt as often as every few days.

A "killer shrimp" that slaughters many creatures without eating them is invading the British Isles, and researchers fear it could wipe out native species.

Scientists in the United Kingdom are deeply concerned about what impact this alien invader from western Asia might have should it gain a foothold in the U.K. or beyond.

The creature classified as Dikerogammarus villosus is actually not a shrimp but another type of crustacean known as an amphipod. Although it reaches only 1.2 inches (3 centimeters) long, it has unusually large and powerful mouthparts to bite and shred its prey, and it often gets called a "killer shrimp" because of its vicious behavior, killing and maiming indiscriminately. [Image of killer shrimp]

"As prey numbers increase, Dikerogammarus appear to increase their attack rate far more strongly than other similar amphipod crustaceans," said freshwater ecologist Steve Ormerod at Cardiff University in Wales.

Bizarrely, D. villosus is so violent that it often kills creatures without eating them – an odd example of killing for killing's sake.

"At present, we have no explanation for this behavior," Ormerod noted. Scientists have speculated the high rates at which it attacks others could help it compete in its environment.

The life of a killer … shrimp

This "killer shrimp" is originally from near the Black and Caspian Seas. However, in the past 20 years, it spread across central and western Europe via waterways such as the Danube and Rhine.

It has many traits that make it a daunting invader: It grows rapidly, reaches sexual maturity early, can reproduce all year round, lays nearly 200 eggs per clutch, has wide food preferences, and can tolerate wide ranges of water temperature, salt and oxygen levels. And the whammy: It can survive for at least six days out of water.

"Dikerogammarus appears to be an extremely voracious predator and competitor, killing and eating its prey at a far faster rate than other similar animals," Ormerod said. "It also breeds very rapidly, and has quickly established large populations that appear so far to be unchecked by natural enemies."

Invading England

Now scientists find this alien invader has reached the British Isles. Researchers found it along the margins and in the open water of a large reservoir in England last September and in two sites in Wales in November. [Album: Killer Shrimp and Other Invaders]

"There are now major concerns that it might start to colonize other locations because it has reached such large densities at least at one of the occupied locations — in the 200-hectare lake [494 acres] at Cardiff Bay, intensively used by people for recreation," Ormerod told LiveScience. "Numbers reach up to 4,000 individuals per square meter."

The intruder may have invaded the British Isles by hitchhiking in some equipment or ballast water on a European boat, Ormerod suggested.

"Those involved with conserving and managing biodiversity and fisheries in the United Kingdom's freshwaters fear that, by acting as a very successful predator, Dikerogammarus could reduce populations of other invertebrates and fish, change their species composition in affected waters, and damage freshwater ecological health," Ormerod said. "Evidence from occupied sites in mainland Europe suggests that these fears are justified."

Currently, scientists in the British Isles are focusing on educating anglers, boaters and other participants in recreational water activities about biosecurity — "making sure that equipment is washed down and dried before being used in other locations," Ormerod said. "However, breakout to other locations is now high-risk, so we also need to understand the likely impacts and develop control and eradication methods as far as possible."

Ormerod does mean as far as possible, including across the Atlantic Ocean. Although this intruder is not near North America, "the lessons from other invasive species is that true control and eradication is very seldom possible," he said.

Other invaders from the native range of D. villosus have reached North America, "notably the zebra and quagga mussels, with drastic results, and my guess is that North American freshwater biologists will already be looking out for Dikerogammarus," Ormerod said.

Fossils of a 10-legged wormy creature that lived 520 million years ago may fill an important gap in the history of the evolution of insects, spiders and crustaceans.

The so-called walking cactus belongs to a group of extinct worm-like creatures called lobopodians that are thought to have given rise to arthropods. Spiders and other arthropods have segmented bodies and jointed limbs covered in a hardened shell.

Before the discovery of the walking cactus, Diania cactiformis, all lobopodian remains had soft bodies and soft limbs, said Jianni Liu, the lead researcher who is affiliated with Northwest University in China and Freie University in Germany.

"Walking cactus is very important because it is sort of a missing link from lobopodians to arthropods," Liu told LiveScience. "Scientists have always suspected that arthropods evolved from somewhere amongst lobopodians, but until now we didn't have a single fossil you could point at and say that is the first one with jointed legs. And this is what walking cactus shows." [Image of walking cactus fossil]

Leggy find

Liu and other researchers described the extinct creature based on three complete fossils and 30 partial ones discovered in Yunnan Province in southern China. The walking cactus had a body divided into nine segments with 10 pairs of hardened, jointed legs, and it measured about 2.4 inches (6 centimeters) long. 

It's not clear how the leggy worm made its living. It could have used its tube-like mouth called a proboscis to suck tiny things from the mud, or it may have used its spiny front legs to grab prey, Liu said.

Clues to arthropod evolution are preserved in modern-day velvet worms, which are considered the only living relative to all arthropods. Once mistaken for slugs, these land-dwelling worms are almost entirely soft-bodied except for hardened claws and jaws.

Where spiders, insects and others came from

The discovery of the walking cactus helps fill in the evolutionary history between the velvet worms and modern arthropods, which, in terms of numbers and diversity, are the most dominant group of animals on the planet, according to Graham Budd, a professor of paleobiology at Uppsala University in Sweden, who was not involved in the current study.

The walking cactus is the first and only case of hardened, jointed limbs built for walking appearing in a creature that is not recognizable as an arthropod, Budd said.

But Budd is not convinced that, as the researchers argue, the walking cactus's hardened legs were passed directly down to modern arthropods.

"I am not persuaded that it is a direct ancestor or as closely related to living arthropods as they suggest," he told LiveScience. "I would like to see more evidence; the great thing is a lot more material keeps coming up."

For instance, it is possible that the walking cactus is less closely related to modern arthropods, and that hardened legs evolved multiple times. It is also possible that the bodies of primitive arthropods hardened before their legs did, Budd said.

New fossils, particularly from China, have helped clarify the evolutionary history of arthropods, and in the last decade or so, scientists have come to more consensus regarding that history, he added.

You can follow LiveScience writer Wynne Parry on Twitter @Wynne_Parry.

This fall millions of crabs will undertake an arduous, miles-long migration to the Indian Ocean where they reproduce. Now scientists have figured out the key to the athletic feat: crabby hormones.

When monsoon rains set in on Christmas Island, south of Indonesia, the teensy crabs, just 8 inches (20 centimeters) long, go from a leisurely existence of hanging out in their burrows on the floor of the rain forest, to scuttling along for miles toward the coast. [Top 10 Most Incredible Animal Journeys]

"Their migration is extremely energetically demanding, since the crabs must walk several kilometers over a few days," said researcher Simon Webster, an endocrinologist at Bangor University in North Wales, U.K.

Scientists had long puzzled over what changes in the crabs' bodies took place to enable this stark change in behavior.

Webster and Steve Morris from the University of Bristol in England looked at the so-called crustacean hyperglycemic hormone (CHH), which, among other things, controls the conversion of stored energy in the muscles (called glycogen) into usable fuel (called glucose). It's the equivalent of a marathoner consuming a sugary gel to keep their muscles going.

The researchers expected that during the epic migration, which Webster said is the equivalent of humans running successive marathons, the crabs would have high CHH since their bodies would need tons of fuel.

However, the red crabs (Gecarcoidea natalis) showed higher levels during the dry season, when they are relatively inactive.

To figure out the paradox, they exercised crabs in the field during the wet and dry seasons, finding CHH increased for both scenarios. Perhaps the reason they didn't see this hormone signal in the field earlier was because the red crabs had been munching on snacks along the way so they didn't need to use their stored energy. To find out, the team injected the crabs with glucose during the exercise stints, finding during the wet season there was no such spike in CHH, suggesting the glucose turned off the release of stored energy from the crabs' muscles.

Essentially, the crabs don't want to use up all of their onboard "gel packs." So if there's a little bit of glucose available, their bodies' save the glycogen for later. The result ensures they can complete the 3-mile (5-kilometer) journey.

The research, funded by a Natural Environment Research Council (NERC) grant, is published in the September issue of the Journal of Experimental Biology.

• Animal Senses Humans Don't Have
• 10 Amazing Things You Didn't Know About Animals
• 10 Species You Can Kiss Goodbye

A previously unknown species of an eyeless crustacean was discovered lurking inside a lava tube beneath the seafloor.

The creature, named Speleonectes atlantida, lives in the Tunnel de la Atlantida, the world's longest submarine lava tube on Lanzarote in the Canary Islands off the western coast of northern Africa. The discovery, which has implications for the evolution of an ancient group of crustaceans, will be detailed in September in a special issue of the journal Marine Biodiversity.

While in the cave, the international team of scientists and cave divers also discovered two previously unknown species of annelid worms.

Tunnel life

The 5,000-foot (1,500 meter) long tube where the crustacean lives formed some 20,000 years ago when the Monte Corona volcano erupted on the island of Lanzarote. The erupted molten rock flowed across the land and into the ocean.

"The tunnel formed because the lava on the surface cooled and solidified faster than lava in the center of the stream," said study researcher Stefan Koenemann of the University of Veterinary Medicine Hannover, in Germany. "At present, there are no more active volcanoes on Lanzarote. The last eruptions took place in the 18th century."

The tunnel's newly identified inhabitant, which is less than an inch (10 to 20 mm) long, belongs to the class Remipedia, whose crustacean members live only in cave systems. Like this species, most other remipedes lack eyes and are hermaphrodites (equipped with both male and female sexual organs).

And similar to its relatives, S. atlantida is adapted for life in a dark, dismal cave. With long antennae sprouting from its head and plenty of sensory hairs along its body, the animal can easily feel its way along the dark tunnel.

Organisms like S. atlantida also must be savvy hunters to nab food where resources are limited, Koenemann said.

"Apart from its powerful raptorial head limbs, which are used to hunt and seize other cave animals up to twice their body size, remipedes like Speleonectes are also filter- or particle feeders and scavangers," Koenemann told LiveScience. "In other words, they are capable of using and ingesting a large variety of food types."

Ancient and isolated

S. atlantida looks similar to the only other remipede, called Speleonectes ondinae, found in this lava tunnel.

Since most remipede species, about 20, live in marine caves in the Caribbean, scientists think the two Canary Island cave dwellers are relics from long ago, isolated by Earth's ever-shifting continents, which were once all joined.

"The previously known species in the tunnel, Speleonectes ondinae, was considered an isolated relic that became separated from the main distribution area in the larger Caribbean region a very long time ago, presumably more than 200 million years ago, when the continental plates began drifting apart," Koenemann said.

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The fossilized remains of a tiny 100 million-year-old crustacean reveal evidence of what to her at least would have been giant sperm, measuring perhaps as long as her body. While the sperm itself was not preserved, 3-D images of the female's specialized receptacles indicate she had just finished having sex and that they were filled with sperm that has since degraded. (The oldest direct evidence of sperm comes from a springtail living some 40 million years ago, according to the researchers.) Called Harbinia micropapillosa, the tiny organism now found to bear evidence of degraded sperm was also an ostracod, crustaceans ranging in size from smaller than a poppy seed to as large as a meatball. The organisms are still around on Earth today and are equipped with up to eight pairs of appendages along their bivalve bodies. They are known for their supersized sperm relative to their body size, reaching a record-breaking 10 body lengths, or 0.2 inches (6 millimeters), in Propontocypris monstrosa. The males are likewise well-endowed, having correspondingly large copulatory organs to cope with their sperm, said lead researcher Renate Matzke-Karasz of Ludwig Maximilians University in Munich, Germany. (When sperm length reaches that of the organism's body, it can arguably be called "giant," Matzke-Karasz said.) Matzke-Karasz and her colleagues used holotomography, a type of 3-D scanning method, to look at the reproductive organs of specimens of H. micropapillosa (male and female remains), along with those of a living relative called Eucypris virens. Living ostracods like E. virens have reproductive organs separated into two systems located on both sides of the body. The males have two sperm pumps and two copulatory organs (aka penises), while females have two vaginal openings connected to long ducts that end in semen receptacles. The researchers found that three specimens of male H. micropapillosa contained hollow tubes at the back of the body, which were likely sperm pumps. The two female specimens showed paired cavities that corresponded with seminal receptacles, which are only known from ostracods reproducing with giant sperm. "The receptacles must have been filled with sperm in order to be preserved as two cavities," the researchers write. Empty receptacles are folded up inside the body and only take on their distinctive shape and size after sperm gets transferred into them. And if the ancient ostracods copulated like their modern counterparts, it would've been arduous. "The copulation itself takes a long time. They have to find each other, and during the act the female has to actively 'agree,' because otherwise she simply closes her carapace," Matzke-Karasz told LiveScience. "The copulation when it starts seems to be energetically costly because it can last up to one hour." The new research, detailed in the June 19 issue of the journal Science, shows ostracods were already reproducing with giant sperm well into the Mesozoic Era even though sperm and its associated organs can be energetically draining to organisms. "Now we can show that in spite of the costs, it must be a successful way to reproduce, since it 'survived' for such a long time," Matzke-Karasz said.

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This Behind the Scenes article was provided to LiveScience in partnership with the National Science Foundation. They go by various names — crawfish, crayfish, crawdads, mudbugs — but one thing is common to all discussions of the lobster-like freshwater crustacean: they invoke imagery of the Louisiana bayous. This surely comes from the fact that one of the most famous crayfishes, the Louisiana crayfish Procambarus clarkia, is a staple in Cajun cuisine. However, as we found out through our NSF-IGERT research, Louisiana crayfish should also invoke imagery of rice paddies in China.     Although native to the United States, the Louisiana crayfish has been introduced for aquaculture in countries around the world including Brazil, Portugal, Spain, France, Kenya, and Uganda, among others.   The Louisiana Crayfish, xiao long xia (literally “small dragon shrimp” in Mandarin), has been present in China since 1940. As they do in Louisiana, crayfish in China have considerable economic value as a food source.   However, as an exotic invader, crayfish also threaten native Chinese fishes and feed on several important local plants including rice and lotus crops. Crayfish have also been suggested as a possible biocontrol agent for the snail vector of the human disease schistosomiasis. Yet the overall costs and benefits of crayfish introduction in China remain largely undocumented.   Crayfish: the good, the bad, and the financial With the encouragement of our advisor David Lodge, we became interested in the status of the Louisiana crayfish in China. We made a preliminary research trip to central China in the summer of 2008, during which we were able to experience local crayfish culture first hand. Our host was Jianqing Ding, an expert in biological control of invasive plants at the Wuhan Botanical Garden of the Chinese Academy of Sciences. We conducted interviews with scientists and fishermen and traveled across southeastern China to collect specimens and examine potential sites for studying crayfish.   The Chinese ecologists we spoke to all acknowledged the negative ecological impacts caused by Louisiana crayfish. In light of this and published negative impacts of crayfish introductions in Europe and South America, we were surprised by how welcome this exotic crayfish was in the Chinese community, even among rice farmers whose crops were being destroyed.   Although farmers recognized that aquatic plant destruction and drained ponds due to the burrowing activity of crayfish as considerable negative impacts, crayfish-stocked ponds were abundant. Farmers did not hesitate to stock crayfish in some ponds and use aggressive chemical treatments to eradicate them from others. We witnessed crayfish-induced destruction on our first trip to a rice paddy. As we hiked through an invaded field in which much of the vegetation had been destroyed, we noted that the water levels were obviously low, and the water present was murky.   As we were leaving, a neighbor who had heard that we were studying crayfish came up to us and was excited to take us to his pond where he had begun to stock them — and asked us for advice on how to improve his yields! When we asked why he would introduce the crayfish with the knowledge that they could devastate nearby agriculture, he admitted that the business of selling crayfish was too lucrative to pass up. Another rice farmer explained that if he had the necessary resources, he said he would sell only crayfish and eliminate rice farming all together. Culture, economics and taste As we traveled the Chinese countryside and met more farmers and fishermen with similar stories, we began to understand the pervasive point of view, one that had not crossed the minds of these two American ecologists.   This novel perspective on invasive species was perhaps most elegantly stated as we made small-talk with a taxi driver in Wuhan. As we explained our research through an interpreter, the taxi driver smiled and asked "Can they really be considered a problem if people eat them?" Perhaps this beneficial perception of crayfish explains why there have been fewer ecological impact studies conducted in China than in other countries.   The larger lesson learned was that exotic species need to be considered in the full context of their introduced range: local culture and economics are important in addition to ecology. Although this message is becoming more common in the invasive species literature, it wasn’t until our trip to China that we truly understood it.   This real world experience is at the heart of our IGERT program, GLOBES (Global Linkages of Biology, the Environment, and Society), which emphasizes an interdisciplinary approach to issues of human and environmental health. We are currently planning more trips to China to continue researching the Louisiana crayfish introduction, and we are enlisting help from our fellow GLOBES students in developing a more interdisciplinary project for the future.   We aim to use Louisiana crayfish in China as a case study to emphasize how regional and cultural contexts intimately relate to the ecology of species invasions.

Editor's Note: This research was supported by the National Science Foundation (NSF), the federal agency charged with funding basic research and education across all fields of science and engineering. See the Behind the Scenes Archive.

Should crabs be protected from pain? Vote below. 

A favored method of preparing fresh crabs is to simply boil them alive. A longstanding related question: Do they feel pain?

Yes, researchers now say. Not only do crabs suffer pain, a new study found, but they retain a memory of it (assuming they aren't already dead on your dinner plate). The scientists say its time for new laws to consider the suffering of all crustaceans.

The study involved using wires to deliver shocks to the bellies of hermit crabs, which, being hermits, often take up residence in left-behind mollusc shells. The crabs that were shocked scampered out of their shells, "indicating that the experience is unpleasant for them," the scientists concluded; unshocked crabs stayed put.

Another test was run to see what would happen if a mild shock was delivered, one just below the threshold that would cause the crabs to leave home. These mildly shocked crabs, along with crabs that had not been shocked, were then offered a new home. The typical reaction: They'd go inspect the new shell. Significantly, those that had been shocked were more likely to pack up and move to the new residence compared to those that hadn't been shocked.

"There has been a long debate about whether crustaceans including crabs, prawns and lobsters feel pain," said study researcher Bob Elwood of Queen's University Belfast in the UK.

"We know from previous research that they can detect harmful stimuli and withdraw from the source of the stimuli but that could be a simple reflex without the inner 'feeling' of unpleasantness that we associate with pain," Elwood explained. "This research demonstrates that it is not a simple reflex but that crabs trade-off their need for a quality shell with the need to avoid the harmful stimulus."

The findings are detailed in the journal Animal Behaviour.

Interestingly, scientist don't fully understand pain in humans. It is felt when electrical signals are sent from nerve endings to your brain, which in turn can release painkillers called endorphins and generate physical and emotional reactions. The details remain unclear, which his why so many people suffer chronic pain with no relief.

At any rate, Elwood compared the results of the crab study to how you might react to a painful experience.

"Humans, for example, may hold on to a hot plate that contains food whereas they may drop an empty plate, showing that we take into account differing motivational requirements when responding to pain," he said. "Trade-offs of this type have not been previously demonstrated in crustaceans. The results are consistent with the idea of pain being experienced by these animals."

A Norwegian study in 2005 concluded lobsters react to boiling water or other pain stimuli, but that they don't have the emotional capacity to experience it as pain in the way higher animals do. But a study by Elwood and colleagues in 2007 found prawns were irritated when their antennae were treated with acetic acid, and after a local anesthetic, they'd stop rubbing the antennae. He said this was evidence that they suffer pain, and that lobsters likely feel pain, too.

Elwood thinks its time for some crustacean empathy.

"Millions of crustacean are caught or reared in aquaculture for the food industry," he said. "There is no protection for these animals (with the possible exception of certain states in Australia) as the presumption is that they cannot experience pain. With vertebrates we are asked to err on the side of caution and I believe this is the approach to take with these crustaceans."

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Robert Roy Britt is the Editorial Director of Imaginova. In this column, The Water Cooler, he looks at what people are talking about in the world of science and beyond.

Among the greatest mysteries in zoology for more than a century have been vaguely shrimp-like creatures known as y-larvae.

Although these microscopic beasts are clearly young crustaceans, no one knew what the adult forms looked like.

Now researchers may have solved this puzzle by dosing the y-larvae with a hormone that forced them to go through a growth spurt.

The result — simple, pulsing, slug-like masses of cells that were "mind-blowing" to the scientists. These surprisingly simple creatures — far simpler than their larval stage — may be parasites found worldwide.

Dizzying diversity

Y-larvae, or facetotectans, were first discovered in 1899. There were once x-larvae as well, the 'x' and 'y' both denoting something mysterious. Later on, the adult form of the x-larvae were found, but bafflingly, even after intense searches, no one knew what y-larvae grew up to be, so they kept their name.

These critters are just a few hundred microns large, or roughly the size of the period at the end of this sentence. They occur with dizzying diversity in coral reef areas, and are found in all oceans, from the poles to the tropics. Their commonplace nature suggests the adults play a major role in ecosystems around the globe.

To find out what these y-adults might be, an international team of scientists used nets to collect more than 40 species of y-larvae from a marine station at Sesoko Island near Okinawa, Japan. As they were gathering the creatures, a cyclone approached.

"It was predicted to hit the marine station five days after the arrival of our team," said researcher Henrik Glenner, a molecular biologist at the University of Copenhagen in Denmark. "This put us under substantial time pressure, because we knew that it was impossible to catch the y-larvae after the cyclone had passed. Therefore, we had to work during the nights."

Safe back in the lab

The researchers next exposed y-larvae to a crustacean hormone that encouraged them to mature. The creatures metamorphosized into a juvenile form, dubbed "ypsigons," unexpectedly shedding their exoskeletons to become wriggling, eyeless, limbless creatures that resemble parasitic crustaceans.

At first the researchers thought their eyes were tricking them, but eventually "the juvenile literally crawled out of the old larval carapace," Glenner recalled. "It was only after several repeated experiments we actually believed what we saw. That feeling was a mind-blowing experience."

The fact that ypsigons are vastly different and far simpler than y-larvae might help explain why the adult versions of these creatures have escaped detection for so long. These are so simple compared with y-larvae that they even lack digestive tracts and nervous systems.

Ypsigons could make do without a digestive tract by directly absorbing nutrients from their surroundings, They might develop a nervous system later on in life, "but not necessarily," Glenner said.

"I know it sounds strange, but in some adult parasitic barnacles — rhizocephalans, which parasitize other crustaceans — there are no traces of a nervous system either," Glenner told LiveScience. "This is possible because their behavior as adults is restricted to certain coordinated movements when they release their larvae."

Probably parasites

As the final adult stage of the y-larvae are probably parasites, future efforts to uncover these y-adults — to solve this mystery once and for all — will aim to identify their hosts by screening coral reef animals for y-larvae DNA.

"These parasites could play a very important role in the wild," said researcher Jens Høeg, a marine zoologist and invertebrate morphologist at the University of Copenhagen in Denmark. "They should not be seen as evil or bad. Wherever these parasites are, be they in sea urchins or sea stars or corals, they are probably important in making up what we consider a normal, healthy coral reef."

Høeg, Glenner and their colleagues Mark Grygier and Yoshihisa Fujita detailed their findings May 19 in the journal BMC Biology. They were supported by the Carlsberg Foundation in Denmark and the Lake Biwa Museum in Japan.

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A fossil of a new crab species reveals the itsy-bitsy crustaceans inhabited towering sponge reefs during the Jurassic Period, where they made tasty snacks for ichthyosaurs and other ancient reptiles.

The fossil was discovered in eastern Romania within cylindrical reef structures about 100 feet (30 meters) across and just as tall, which were once blanketed by deep ocean. It represents a new species within the oldest lineage of true crabs that lived 150 million years ago when dinosaurs walked the Earth.

Dubbed Cycloprosopon dobrogea, the primitive crab was built for sidling in and out of crevices in reefs, with a flattened body just under a half-inch (6 millimeters) long. Exactly how the crab moved about, however, is not known, as this species and other family members had no legs extending from the carapace, or outer body covering.

"They probably were hiding in the small cracks and crevices within the sponge reef itself," said lead researcher Carrie Schweitzer, a geologist at Kent State University in Ohio.

The underwater hideouts would've proved critical to survival in the face of ancient reptiles nosing around for tasty morsels.

"These crabs in the Jurassic were living in much deeper water than a dinosaur would've been, but something like an ichthyosaur or a plesiosaur would certainly have been eating crabs," Schweitzer told LiveScience.

Schweitzer has uncovered other Jurassic crabs in this area and elsewhere, indicating, she says, that the crustaceans were much more diverse and plentiful than scientists had thought.

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A male crayfish with larger-than-normal claws typically needs only to flash his menacing weapons to drive opponents away. Now researchers find these critters are frequently bluffing—the enlarged claws often aren't stronger at all. These findings raise the question of how often males in the animal kingdom are just bluffing with their natural weaponry. "Dishonesty during disputes may be far more prevalent that we previously imagined," said researcher Robbie Wilson, a zoologist at the University of Queensland in Australia. Death or dismemberment Wilson and an international team of researchers investigated the Australian slender crayfish (Cherax dispar). The small, lobster-like crustaceans are extraordinarily aggressive beasts, with combat often resulting in death or the loss of a limb. "When you pick them up, they'll want to take your finger off right away," Wilson said. These two- to three-inch long creatures were collected from the creeks on the sand islands off southeast Queensland. Crayfish are freshwater creatures, while lobsters are marine animals. The bluffing finding emerged when the scientists randomly pit 32 adult male crayfish against each other, two at a time, in plastic aquariums. They recorded how often competitive bouts led either to chases or fights. The crayfish were taken out after 10 minutes, to prevent any serious harm. "It felt more like watching sport than doing work," Wilson told LiveScience. "It did seem like we were setting up boxing matches." Squeeze this Wilson and his colleagues also investigated how strong each claw was by getting crayfish to squeeze metal plates in a custom-built sensor. "When you present them with the sensors, they're so aggressive they'll squeeze them as hard as they can, which is luckily what you want to test their strength," Wilson said. Claw size most often determined which crayfish won—if the claws of one crayfish were significantly larger than another's, the other would simply turn and run. "Like most animals, the size of their weapons seemed to determine everything in these crayfish," Wilson said. Pincers reached up to a third of the length of each combatant's body. However, larger claws were not always the strongest pincers, suggesting these weapons are most often used for intimidation rather than combat. "When the claws of each crayfish are roughly the same size, then whoever's stronger prevails," Wilson said. The team's results are detailed in the August issue of the journal American Naturalist. "Such dishonesty is probably more common in nature than most researchers now think," Wilson said. But rooting it out in other creatures might prove difficult. "If such dishonest signals are hard for other competitors to detect, they will be very hard for researchers to detect," he said.

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A sluggish, sick human is easy to spot. But it's harder to tell when a shrimp is under the weather. So one scientist put the little crustaceans on a tiny treadmill to examine how diseases impact their performance.

Humans fighting an infection typically sleep more and are not at top physical performance. "The situation is much more critical for a sick marine crustacean, such as a shrimp, where a decrease in performance may mean the difference between life and death," said David Scholnick, a biologist from Pacific University in Oregon.

The shrimp treadmill, invented and built by Scholnick, allows researchers to measure the activity of an exercising shrimp for a set period of time at known speed and oxygen levels.

"As far as I know this is the first time that shrimp have been exercised on a treadmill, and it was amazing to see how well they performed," Scholnick told Live Science. "Healthy shrimp ran and swam at treadmill speeds of up to 20 meters per minute [66 feet per minute] for hours with little indication of fatigue."

To further challenge the healthy shrimp, the researchers designed a small backpack made of duct tape to add extra load to the shrimp. With the extra weight and lowered oxygen, they were active for up to an hour.

Sick shrimp, however, had reduced aerobic performance. They also had elevated blood lactate levels. Lactate is produced during exercise as a by-product of metabolizing glucose. Infected shrimp are unable to remove it from their tissues efficiently and therefore could not recover from exercise as well as healthy shrimp.

Shrimp dealing with an infection would be less active and might be limited in their ability to migrate, find food and avoid being eaten, Scholnick said. "These studies will give us a better idea of how marine animals can perform in their native habitat when faced with increasing pathogens and immunological challenges."

Original article on Live Science.

At a cement quarry in Israel, researchers have discovered eight previously unknown species of small creatures in a newfound underground cave.

The limestone cave has long been sealed off from it surroundings—even outside water cannot seep through an overlying layer of chalk—and it contains an entire ecosystem unlike anything known.

The newly named Ayalon Cave stretches for about 1.5 miles and is "unique in the world," said Amos Frumkin of the Hebrew University Department of Geography.

A small opening was uncovered at the quarry, leading to the cave, which extends more than 100 yards below the surface. It is situated between Jerusalem and Tel Aviv.

Scientists found seawater and freshwater crustaceans  in underground lakes that are a brackish mix, as well as a terrestrial scorpion that, owing to the eternal darkness in the cave, is blind. The new species were all found alive except the scorpion, but live scorpions will be found in further expeditions, said university researcher Hanan Dimentman.

All the animals are thought to have been isolated for millions of years. Other scientists are now working to classify them.

"The eight species found thus far are only the beginning" of what promises to be "a fantastic biodiversity," Dimentman said.

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