Blue-lined octopus

The blue-lined octopus (Hapalochlaena fasciata) is one of three (or perhaps four) species of highly venomous blue-ringed octopuses. It is most commonly found around intertidal rocky shores and coastal waters to a depth of 15 metres (49 ft) between southern Queensland and southern New South Wales. It is relatively small, with a mantle up to 45 millimetres (1.8 in) in length. In its relaxed state, it is a mottled yellow-brown with dark blue or black streaks covering the whole body apart from the underside of its arms, but its vibrant blue patches appear as a warning when they feel threatened. Along with its other closely related species, the blue-lined octopus is regarded as one of the most dangerous animals in the sea, and its venom can be fatal to humans. The blue-lined octopus’s saliva contain a special neurotoxin called tetrodotoxin which causes muscle weakness and respiratory failure. It’s so lethal that it’s been estimated that the venom from a single 25 gram octopus can kill about 75 humans.[1] It is one of the most common of several species of blue-ringed octopuses found in Sydney. Their size range from 4.5 cm, of an adult, to 5.5 cm.[2]

Blue-lined octopus
Hapalochlaena fasciata
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Order:	Octopoda
Family:	Octopodidae
Genus:	Hapalochlaena Robson, 1929
Species:	H. fasciata
Binomial name
Hapalochlaena fasciata (Hoyle, 1886)