Blue-ringed octopus, one of the most toxic animals on Earth, bites woman multiple times

Blue-ringed octopuses contain a powerful neurotoxin called tetrodotoxin, which can be lethal to humans in small doses. (Image credit: James Reynolds)

A woman in Australia was recently bitten multiple times by a blue-ringed octopus — one of the world's most toxic animals — and lived to tell the tale.

Blue-ringed octopuses are a group comprising four species: the greater blue-ringed octopus (Hapalochlaena lunulata), the southern blue-ringed octopus (Hapalochlaena maculosa), the blue-lined octopus (Hapalochlaena fasciata) and the common blue-ringed octopus (Hapalochlaena nierstraszi). These octopuses are small enough to fit in the palm of your hand and are covered in tiny rings that flash with an iridescent blue when the animals are threatened. Blue-ringed octopuses also contain tetrodotoxin, a powerful neurotoxin that can paralyze and kill humans even in small doses.

On March 16, the woman was bitten twice on her abdomen by an unknown species of blue-ringed octopus at a beach near Sydney in New South Wales (NSW), Australia. She had collected a small shell while swimming, and when she picked it up to look at it, the tiny cephalopod fell out and landed on her stomach, the NSW Ambulance service wrote on Facebook.

The woman experienced some abdominal pain and was treated with cold compresses before being taken to the hospital to be monitored for more symptoms, according to NSW Ambulance. It is unclear why the woman escaped relatively unharmed.

Related: 30 unusual poisonous animals

Tetrodotoxin stops nerves from signaling to muscles by blocking sodium ion channels. This causes rapid weakening and paralysis of muscles, including those of the respiratory tract, which can lead to respiratory arrest and death. The effects of tetrodotoxin can occur rapidly or have a delayed onset, so death can occur anywhere between 20 minutes and 24 hours after the toxin enters the body, according to the Centers for Disease Control and Prevention (CDC)

There is no known antidote for tetrodotoxin. All health care practitioners can do is provide supportive care or use a ventilator if patients are unable to breathe, according to the CDC.

Blue-ringed octopuses do not create tetrodotoxin themselves. Instead, the toxin is produced by symbiotic bacteria that live in their salivary glands, according to the Australian Institute of Marine Science. Tetrodotoxin is found throughout the octopus's tissues, not just in specific venom glands, which makes them some of the few animals that are both poisonous and venomous. It also means that a person can receive a lethal dose if one of these octopuses touches their skin.

Despite being so toxic, blue-ringed octopuses have caused only three confirmed deaths, according to WebMD.

Blue-ringed octopuses flash their iridescent rings to warn predators of their toxicity. (Image credit: Subaqueosshutterbug / Getty)

The iridescent blue rings that flash on the octopuses' bodies warn predators of their toxicity. They can flash their rings in less than 0.4 seconds, thanks to tiny color-changing organs called chromatophores, which are dotted across the animals' skin.

While blue-ringed octopuses rarely kill people, there have been plenty of close calls.

In 2006, a 4-year-old boy was almost killed after being bitten by an octopus he picked up in a rock pool on a beach in Queensland. The boy vomited several times before developing blurred vision and then losing control of most of his muscles, according to a case report published in the journal Clinical Toxicology. After spending 17 hours on a ventilator, he eventually made a full recovery. 

And in March 2021, a woman was heavily criticized online after sharing a video of herself holding a blue-ringed octopus in Bali, although she did not know it was highly toxic at the time and escaped unscathed, according to Insider.

Blue-ringed octopuses aren't the only animals that contain tetrodotoxin; it can be found in some newts, frogs and puffer fish. 

Harry Baker
Senior Staff Writer

Harry is a U.K.-based senior staff writer at Live Science. He studied marine biology at the University of Exeter before training to become a journalist. He covers a wide range of topics including space exploration, planetary science, space weather, climate change, animal behavior, evolution and paleontology. His feature on the upcoming solar maximum was shortlisted in the "top scoop" category at the National Council for the Training of Journalists (NCTJ) Awards for Excellence in 2023. 

  • Codeman785
    I wonder if the octopus gave warning bites by chance? Or maybe that particular octopus was ill or has some kind of deficiency to not produce enough toxin?
    Reply
  • KuramaKitsune
    There's a difference between venomous and poisonous
    A poison must be consumed or otherwise absorbed to take effect
    A venom may be injected such as through a bite ie: venomous snake
    Certain snake venoms can be swallowed with no ill effect, because they are not poisonous

    Toxins and poisons are similar but different as well
    Toxic refers to the degree of damage to a system
    Toxic can refer to chemical or biological substances
    Whereas poisonous is a more extreme example that says essentially this will absolutely cause damage to a system ie: you.
    Anything is "toxic" given a high enough dosage
    Reply
  • KuramaKitsune
    As the article states these little octopuses as cute as they are are one of the most dangerous creatures we know of as they are both poisonous and venomous not only this but the toxin That is in their bodies is horrifyingly efficient
    Reply
  • jgrigg17
    Growing up in Okinawa, I heard of a handful of deaths related to the blue ringed octopus. My dad was a medic and told me of at least one situation when a few Marines found one and played catch with it.
    Reply
  • Areon
    KuramaKitsune said:
    There's a difference between venomous and poisonous
    A poison must be consumed or otherwise absorbed to take effect
    A venom may be injected such as through a bite ie: venomous snake
    Certain snake venoms can be swallowed with no ill effect, because they are not poisonous

    Toxins and poisons are similar but different as well
    Toxic refers to the degree of damage to a system
    Toxic can refer to chemical or biological substances
    Whereas poisonous is a more extreme example that says essentially this will absolutely cause damage to a system ie: you.
    Anything is "toxic" given a high enough dosage
    Yes, as the article says the octopus is both.
    Reply
  • ShaddupYakhunt
    Codeman785 said:
    I wonder if the octopus gave warning bites by chance? Or maybe that particular octopus was ill or has some kind of deficiency to not produce enough toxin?

    "Blue-ringed octopuses do not create tetrodotoxin themselves. Instead, the toxin is produced by symbiotic bacteria that live in their salivary glands, according to the Australian Institute of Marine Science."
    Reply