Class Cephalopoda

1. Exclusively marine.
2. A mantle encloses a visceral mass.
3. Elongated in the dorsoventral plane.
4. Bilaterally symmetrical.
5. Swim by jet propulsion.
6. Carnivorous.
7. All (except the pearly nautilus) have 2 gills, 2 kidneys and 3 hearts.
8. Blue blooded due to a copper-containing respiratory pigment.
9. The "neck" is either partially or wholly free.
10. Head surrounded by tentacles .
11. Separate sexes.
12. Short life spans.

Cephalopods are the most sophisticated molluscs. They range in size from pigmies the size of a pea to giants as long as 20 meters. Found in all oceans, they are divided into two subclasses, Nautiloidea and Coleoidea. Nautiloideas have 3 species of Nautilus and inhabit the west Pacific and eastern Indian Oceans. Their nervous system is less advanced than other cephalopods and their eyes have no lenses. The Coleoidea includes cuttlefish, squid, octopi and flying squid. Their eyes are highly developed with a retina. Pigment cells, allow for rapid color change for camouflage. The sexes are separate. In the male, one of the tentacles is specialized for depositing spermatazoa into the female's mantle cavity. The female's nidamental glands secrete protective capsules around yolky eggs. The young hatch as minature adults. Cephalopods do not survive breeding.

• The word cephalopod comes from the greek words kephale and podos meaning "head-footed."
• Octopi are very shy and avoid man. Squid bite viciously when handled, but there have been no reliably documented attacks on humans.
• The shells of cephalopods have been internalized or lost.
• Cephalopods move backwards quickly but can move in any direction at slower speeds.

1. Buchsbaum, Ralph et. al. 1982. The Audubon Society Encyclopedia of Animal Life . New York: Clarkson N. Potter, Inc.
2. Lane, Frank W. 1960. The Kingdom of the Octopus. New York: Sheridan House.
3. Larousse Encyclopedia of Animal Life. 1767. London: The Hamlyn Publishing Group Limited.