Introduction to Cephalopods

Indonesia, Oval squid
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Cephalopods are mollusks in the Class Cephalopoda, which includes octopuses, squid, cuttlefish, and nautilus. These are ancient species that are thought to have originated about 500 million years ago. There are about 800 species of cephalopods in existence today.

Characteristics of Cephalopods

All cephalopods have a ring of arms surrounding their head, a beak made of chitin, a shell (although only the nautilus has an exterior shell), a merged head and foot, and eyes that can form images.

Cephalopods are intelligent, with relatively large brains. They are also masters of camouflage, changing their color and even pattern and texture to match their surroundings. They range in size from less than 1/2 an inch long to about 30 feet long.


  • Kingdom: Animalia
  • Phylum:¬†Mollusca
  • Class: Cephalopoda


Cephalopods are carnivorous. The diet varies depending on the species, but can include other mollusks, fish, crustaceans and worms. Cephalopods can grasp and hold their prey with their arms and then break it into bite-sized pieces using their beaks.


Unlike some other marine invertebrates, there are both males and females in cephalopod species. Cephalopods usually have a courting ritual when they mate and may change into brilliant colors. The male transfers a sperm packet (spermatophore) to the female, the female lays eggs, and the eggs hatch as juveniles.

Cephalopods'¬†‚ÄčImportance to Humans

Humans use cephalopods in a number of ways - some are eaten, and the shell inside the cuttlefish (the cuttlebone) is sold in pet stores as a source of calcium for birds.


  • Encyclopedia of Life. 2010. The Cephalopoda. (Online) Encyclopedia of Life. Accessed January 4, 2010.
  • Vendetti, Jann. 2006. The Cephalopoda. University of California Museum of Paleontology. (Online). Accessed January 4, 2010.
  • Wood, James B. 2010. The Cephalopod Page (Online). Accessed January 4, 2010.