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. 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.[1]