Octopuses have a complex nervous system and excellent sight, and are among the most intelligent and behaviourally diverse of all invertebrates. The siphon is used both for respiration and for locomotion, by expelling a jet of water. They trail their eight appendages behind them as they swim. The soft body can radically alter its shape, enabling octopuses to squeeze through small gaps. Like other cephalopods, an octopus is bilaterally symmetric with two eyes and a beaked mouth at the center point of the eight limbs. The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids.
An octopus ( pl.: octopuses or octopodes ) is a soft-bodied, eight-limbed mollusc of the order Octopoda ( / ɒ k ˈ t ɒ p ə d ə/, ok- TOP-ə-də ).
