The squid is a common name for a group of carnivorous called marine mollusks. Other members of the class are the octopus, cuttlefish, and chambered nautilus. The squids are blue blooded animals because their respiratory system pigment is a copper compound rather than red iron found in mammals.
Squids are able to change color rapidly by contracting and expanding pigment granules.
Squids are usually small, less than 1 foot in length. They have five pairs of arms.