The Blue-Ringed Octopus

Updated: Jul 26, 2021

The blue-ringed octopus, like other octopuses, is a majestic creature. This small species looks adorable, but many have a lot of fears about it because of its deadly poison.

Appearance & Anatomy

There are 10 species of blue-ringed octopus, all of them are smaller than a tennis ball. They are gray to beige with light brown patches, and of course, blue rings that measure less than 2 mm in diameter but are usually not visible. They lighten up when the octopus is agitated, hunting, or feels attacked. It has 3 hearts and transparent-blue blood caused by the respiratory pigment of the octopuses being based on a copper atom. They also have a bird-like beak.


Blue-ringed octopus can be found in the Pacific Ocean, ranging from the Sea of Japan down to the waters of southern Australia, and across from the Philippines to Vanuatu. They live in tide pools and coral reefs, from the shallow flats all the down to 50m (164 ft). During the daytime, they rest and hide under rocks, crevices, shells, or marine debris. Their time to shine is at night, it is when they swim around, hunt, mate, etc.

Mating & fertilization

The male octopus has its third right arm shaped differently than the rest, it has a spoon-like shape at the end and a groove embedded into it. The spoon end is used to “hold” the spermatophores that are slid to the oviduct of the female (it is internal fertilization). The female holds the sperm until she is ready to lay the eggs.

The females guard their eggs until they hatch. Until then, they don’t leave their nest to feed or for any other reason, so by the end of their job guarding the eggs, they die of weakness.

Venom & hunting

The blue-ringed octopus is one of the deadliest animals on the planet. Their venom can kill up to 26 humans within minutes, but that would be very unlikely because they do not hunt humans nor are they aggressive. So if you leave them alone they will do the same to you. Although they have this powerful venom that is 1,000 times more powerful than cyanide, they do not produce venom as other animals like pufferfish, snakes, spiders do. They use other organisms like bacteria, and they hide them in their saliva glands, the toxins that are produced are called TTX or tetrodotoxin.

They have two different venom glands, with two different functions. One of them is for hunting and they use it on their prey, and the other one it is extremely toxic and used for self-defense.

When a blue ring is hunting it changes color (due to a pigment cell known as chromatophores), and their rings “light up” because it is ready to spit its venom. It jumps on its prey, uses its bird-like beak to make a hole in the exoskeleton, and then spits saliva into it. Its poisonous saliva attacks the nervous system, stopping the nerve impulses, making it paralyzed.

Again, when seeing a blue-ringed octopus, keep your distance, you don’t want it to feel attacked by your presence. Even though the venom is powerful, its bite is painless, and you may not realize you have been bitten until you are paralyzed. There have not been known deaths from blue-ring since the 1960s.


Their diet is very simple and consists of different types of crabs, like hermits and small crabs, and shrimps. And all their digestion is done through their donut-shaped brain.



Image source (He is an awesome photographer, check his Instagram page)

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