Don’t let the beau­ty or size of the blue-ringed octo­pus fool you. The body of a tiny octo­pus is not much larg­er than a ten­nis ball, and may be the size of a coin. Despite the bright beau­ti­ful appear­ance, this octo­pus is extreme­ly poi­so­nous.

blue-ringed octopus

They are native to the Pacif­ic, from Aus­tralia and Indone­sia to the Philip­pines, Japan and South Korea. They live in coral reefs and water bod­ies, where they hide in crevices or shells. They usu­al­ly eat small crus­taceans such as crabs and shrimp and can live for about two years.

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The blue-ringed octo­pus is actu­al­ly more than one species. There are two species that are known as blue-ringed octo­pus­es: Hapalochlae­na lunula­ta and Hapalochlae­na mac­u­losa. In addi­tion, there are two oth­er con­firmed species that belong to the same genus, Hapalochlae­na.

Dangerous poison octopus

In addi­tion to their strik­ing col­oration, the blue-ringed octo­pus is best known for its high­ly tox­ic ven­om. Its ven­om is 1,000 times stronger than cyanide, and each octo­pus has enough ven­om to kill over 20 peo­ple in a mat­ter of min­utes.

The dead­ly ven­om is a pow­er­ful neu­ro­tox­in called tetrodotox­in, sim­i­lar to that of puffer­fish. Although their bite can be high­ly tox­ic, blue-ringed octo­pus­es are gen­er­al­ly not dan­ger­ous to humans; they usu­al­ly do not bite unless pro­voked.

So what hap­pens if a per­son is bit­ten by all of them? The poi­son lasts from 12 to 48 hours, depend­ing on the per­son­’s weight and the amount of poi­son. The ven­om is a post­sy­nap­tic block­er, which means it blocks neu­ro­trans­mit­ters, or nerve sig­nals, in the body. This pro­vokes the so-called “flac­cid paral­y­sis”, which, although it does not affect the heart, but affects the diaphragm, so the per­son stops breath­ing. This hap­pens a few min­utes after the bite.

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Oth­er signs of flac­cid paral­y­sis may include nau­sea, blurred vision, or dif­fi­cul­ty swal­low­ing. The bad news is that there is no anti­dote, so emer­gency care is need­ed imme­di­ate­ly.

poisonous octopus

“Because they are noc­tur­nal, they are very shy. You real­ly have to be tena­cious to get bit­ten,” says Morse. “The poi­son is very potent, and there is no anti­dote. But if the bit­ten per­son can get life-sav­ing pro­ce­dures, they will be fine.”

The good news is that humans are only bit­ten a few times a year, and there are only three known deaths from blue-ringed octo­pus bites.

blue rings

Accord­ing to Morse, one of the mys­ter­ies of the blue-ringed octo­pus is how exact­ly it gets the poi­son and when. We know that octo­pus­es do not pro­duce poi­son them­selves. Instead, it is pro­duced by bac­te­ria in their sali­vary glands. How­ev­er, it is still unclear where these bac­te­ria come from or how the poi­son is passed from par­ent to child, as even the lar­vae in the eggs pro­duce the poi­son. But as long as they pro­duce poi­son, they will remain one of the dead­liest ani­mals in the ocean.

Con­tin­ue Read­ing: The Mim­ic Octo­pus Is a Mas­ter of Mim­ic­k­ing Oth­er Ani­mals