Changes are usually initiated by visual input. In the octopus, the chromatophores consists of three sacs containing different colours. These are activated and the colours are adjusted until the octopus is camouflaged. Colouration, scientists now believe, also indicates an octopus' mood. This gives the cephalopods the ability to communicate by using colour changes.
Cephalopods are all carnivorous.
A radula is present, but even more important is the pair of powerful beak-like jaws that enable the animal to bite and tear apart their food. The squid prey on fish and various invertebrates. When going after fish, squid dash in, grab a fish, pull it in and bite a triangular chunk out of its neck, thus severing its nerve cord. Squid possess ten arms arranged in five pair around their head. The eight short heavy appendages are called arms.