So, What is a Squid?

Cephalopoda

Coleoidea

Characteristics

Propogation

Food

Geography

The Cephalopoda is an ancient and very successful group of the Mollusca. They have been among the dominant large predators in the ocean at various times in geological history. Two groups of cephalopods exist today: The extant Nautiloidea, containing the pearly nautiluses which are phylogenetic relicts, are represented by only a few species, and the Coleoidea.

The Coleoida group contains the squids, cuttlefishes, octopods and vampire squids which are represented by about 700 species. Cephalopods are the most active of the molluscs and some squids rival fishes in their swimming speed. Although there are only about 700 species of living cephalopods, they occupy a great variety of habitats in all of the world's oceans. Individual species are often very abundant and provide major targets for marine fisheries.

Coleoida Characteristics
  1. A funnel derived from the molluscan foot.
  2. Circumoral arms that are probably derived from the molluscan head.
  3. Chitinous beaks.
  4. Shell bearing a phragmacone and siphuncle (lost in most Recent cephalopods).
  5. Image-forming eyes.

All squid move through the ocean using a jet of water forced out of the body by a siphon. Many squid prefer to move about in very deep water where the water temperature is colder. Recent studies indicates the blood of deep water squids does not carry oxygen very well at higher temperatures. Those squid will actually suffocate in warm water. There are as well warm water squid that swim closer to the surface. Warm water squid are migratory since water temperature changes more dramatically nearer to the surface.

Squid are especially carnivorous. They eat fish, other squid, and, in the case of the largest species, whales.

Different species of squid are seen in the seas of the entire world. They have evolved to take advantage of many different environmental conditions. Their geography is more interesting at the species specific level.

Click on a word in the left column to learn more about squid on the right!