Blue-ringed octopuses, comprising the genus Hapalochlaena, are four 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 that change colour dramatically when threatened. They eat small animals, including crabs, hermit crabs, shrimp, and other crustaceans.
They are recognised as one of the world’s most venomous marine animals. Despite their small size—12 to 20 cm (5 to 8 in) – and relatively docile nature, they are dangerous to humans if provoked and handled because of their venom which contains the powerful neurotoxin tetrodotoxin.