Picture Courtesy of The University of Hawaii

Class Cephalopoda includes marine animals that differ from other mollusks because they are built for speed and agility. They have large brains enclosed in cartilaginous brain cases and sense organs, and most either have an internal shell, like a squid, or lack a shell, like an octopus. All cephalopods are predators, and use jaws and radula to crush and rip prey. Like bivalves, they are able to move by taking water into the mantle cavity and shooting it back out. Because of a developed brain, good eye sight, and sense organs, cephalopods are considered to be one of the most advanced vertebrates.

Cephalopods are in the phylum Mollusca. All mollusks have a muscular foot used for moving and a mantle, an outgrowth that covers the animal. Many mollusks have an external calcium carbonate shell that is produced by the mantle. The gill of a mollusk extracts oxygen from the water and disposes of waste. All species of the phylum Mollusca have a complete digestive tract, spanning from the mouth to the anus. Many also have a radula, a unique organ, mostly composed of chitin, in the mouth that allows the animal to scrape food from surfaces, especially the ocean floor, by sliding back and forth. Mollusks have a coelom, but the coelom is made from cell masses, making all species in this phylum protosomes. All organs are suspended in this coelom, between the outer covering and the digestive tube of the animal. However, animals in this phylum are unique to coelomates in that they lack body segmentation. There are seven classes in this phylum.

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