Squid Squid Squid are cephalopods in the order Teuthida with elongated bodies, large eyes, eight arms and two tentacles. Like all other cephalopods, squid have a distinct head, bilateral symmetry, and a mantle. They are mainly soft-bodied, like octopuses, but have a small internal skeleton in the form of a rod-like gladius or pen, made of chitin. Squid can change colour for camouflage and signalling. Some species are bioluminescent, using their light for counter-illumination camouflage. Squid are members of the class Cephalopoda, subclass Coleoidea. The squid orders Myopsida and Oegopsida are in the superorder Decapodiformes (from the Greek for "ten-legged"). Two
Japanese flying squid the squid has a siphon, a muscle which takes in water from one side, and pushes it out the other side: jet propulsion. The squid has eight arms and two tentacles with suction cups along the backs. In between the arms sits the mouth, or beak. Inside the mouth is a tooth-tongue-like appendage called the radula. Squid have ink sacs, which they use as a defense mechanism against possible predators. Squid also have three hearts. The age of a squid can be determined on the basis of its growth rings, or statoliths, when additions are appended daily to the balance