Blue-ringed octopus

Blue-ringed octopuses, comprising the genus Hapalochlaena, are four extremely 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 that change color dramatically when the animal is threatened. They eat small crustaceans, including crabs, hermit crabs, shrimp and other small sea animals. They are one of the world's most venomous marine animals. Despite their small size——and relatively docile nature, they are very dangerous to humans if provoked when handled because their venom contains the powerful neurotoxin tetrodotoxin. The species tend to have a lifespan of approximately two to three years. This may vary depending on factors such as nutrition, temperature and the intensity of light within its habitat. The genus was described by British zoologist Guy Coburn Robson in 1929. There are four confirmed species of Hapalochlaena, and six possible but still undescribed species being researched: Greater blue-ringed octopus (Hapalochlaena lunulata) Southern blue-ringed octopus or lesser blue-ringed octopus (Hapalochlaena maculosa) Blue-lined octopus (Hapalochlaena fasciata) Hapalochlaena nierstraszi was documented and described in 1938 from a single specimen found in the Bay of Bengal, with a second specimen caught and described in 2013. Blue-ringed octopuses spend most 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. If they are provoked, they quickly change color, becoming bright yellow with each of the 50–60 rings flashing bright iridescent blue within a third of a second as an aposematic warning display.