Blue-ringed octopus (Hapalochlaena) is a highly venomous species of octopus that are found in tide pools and coral reefs in the Pacific and Indian Oceans, from Japan to Australia. They can be identified by their yellowish skin and characteristic blue and black rings. They eat small animals, including crabs, hermit crabs, shrimp, and other crustaceans.
They are recognized as one of the world’s most venomous marine animals. Despite their small size and relatively docile nature, they are dangerous to humans if provoked and handled because of their venom which contains the powerful tetrodotoxin. Tetrodotoxin causes severe and often total body paralysis. Tetrodotoxin envenomation can result in victims being fully aware of their surroundings but unable to breathe. Because of the paralysis that occurs, they have no way of signaling for help or any way of indicating distress. This effect, however, is temporary and will fade over a period of hours as the tetrodotoxin is metabolized and excreted by the body.
Blue-ringed octopuses spend much of their time hiding in crevices while displaying effective camouflage patterns with their dermal chromatophore cells. Like all octopuses, they can change shape easily, which helps them to squeeze into crevices much smaller than themselves. This, along with piling up rocks outside the entrance to its lair, helps safeguard the octopus from predators.