A swimmer in Sydney managed to survive multiple highly toxic bites dealt by a blue-ringed octopus.

One of the most toxic creatures on earth is the blue-ringed octopus.

The term "blue-ringed octopus" actually refers to a genus of species and not a single species, all of which have iridescent blue circular markings.

These octopuses are so small that an adult human could hold one in their palm.

Their skin is full of tiny rings that, when threatened, flash an iridescent blue.

Tetrodotoxin, a potent neurotoxin that can incapacitate and kill people even in small doses, is another substance found in blue-ringed octopuses.

The southern Australian waters and the Philippines, as well as Vanuatu, are home to blue-ringed octopuses.

They typically spend the day hiding in cracks or under rocks and come out at night.

They can be found in depths ranging from intertidal flats to 50 meters.

Multiple Highly Toxic Bites

A blue-ringed octopus of an unidentified species bit the woman twice on her abdomen on March 16 in New South Wales, Australia.

The tiny cephalopod fell out of the small shell that she had collected while swimming and landed on her stomach when she picked it up to examine it, according to the NSW Ambulance service Facebook post.

After applying cold compresses to relieve the woman's abdominal discomfort, she was admitted to the hospital to be watched for any further symptoms.

Why and how the woman managed to get away relatively unscathed is unknown.

By blocking sodium ion channels, tetrodotoxin prevents nerves from sending signals to muscles.

This can result in respiratory arrest and death because it quickly weakens and paralyzes muscles, including those in the respiratory tract.

The Centers for Disease Control and Prevention state that because tetrodotoxin's effects can come on quickly or gradually, death can happen anywhere between the range of 20 minutes and 24 hours counted right after the toxin makes it into the body.

Tetrodotoxin has no known cure or remedy.

If patients are unable to breathe, healthcare professionals must only offer supportive care or utilize a ventilator.

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Recorded Fatalities

Tetrodotoxin is not produced by blue-ringed octopuses. Instead, symbiotic bacteria living in their salivary glands produce the toxin, according to the Australian Institute of Marine Science.

The octopus is one of the few animals that are both poisonous and venomous because tetrodotoxin is present throughout the tissues, not just in certain venom glands.

It also means that a person can receive a lethal dose if one of these octopuses touches their skin.

According to WebMD, even though they are highly toxic, blue-ringed octopuses have only been proven to be responsible for three deaths.

Predators are alerted to the octopuses' toxicity by the flashing of their iridescent blue rings on their bodies.

The animals' skin is covered in tiny color-changing structures called chromatophores, which allow them to flash their blue rings for less than 0.4 seconds.

Blue-ringed octopuses are not aggressive and prefer keeping to themselves as long as they are not attacked, Live Science reported.

Related Article: 5 Octopus Facts that Every Cephalopod Enthusiast Must Know