The name cuttlefish is sometimes erroneously applied to the squid. About 100 species of cuttlefish are known, widely distributed in the seas of the Tropic and Temperate zones. They commonly range in size from 15 to 25 cm, but the larger species reach a length of 61 cm.
Cephalopods have the most advanced nervous systems of all invertebrates.
Cuttlefish are the most incredible looking creatures. Cuttlefish normally swim by means of narrow fins that surround the body. Along with squid and octopus, cuttlefish propel themselves through the water at great speed by jetting water from the mantle cavity through a siphon. Cuttlefish have some economic importance, not only for their flesh, which is eaten in many countries, but also for the bone of their internal shell and for the ink they secrete to cloud the water and elude their enemies. The dried ink sacs of the animal yield the brown pigment sepia, and the dried, powdered cuttlebone is used in polishing and in other industrial processes, as well as a source of calcium and salts for captive birds and other animals.