Octopuses

Octopuses are highly intelligent predatory molluscs and one of the largest and most complex invertebrates. They expand the muscular sac surrounding the body to suck in water and then squirt it out through the tubular siphon above the head. This water jet can propel the animal quickly backwards. Octopuses have eight sucker-bearing arms and feed on crabs, lobsters and several species of mollusc, bivalves and snails. The bite of the Blue-Ringed Octopus (pictured) is toxic and can be fatal to humans.