Shells of Galveston Bay
Mollusks Snails, clams, squid are representative of
the Phylum Molluska. Mollusks have been very successful: there are more
species of mollusks in the ocean than on any other group. There are
approximately 125,000 different species.
There are 3 major groupings of Mollusks: The gastropods (or univalves), the Bivalves and the Cephalopods. Gastropods are best known as snails and are the largest, most common, and the most varied group of mollusks. A typical gastropod (which literally means "stomach foot") is basically a coiled mass of vital organs enclosed by a single shell (hence, the name univalve). The shell rests on a creeping foot and is usually coiled.
Bivalves are the clams, oysters, mussels, and scallops. The body is compressed instead of coiled and is placed between two shells (or valves). Some of these invertebrates are burrowers, some live on hard surfaces and attach themselves by either cementing their lower shell (oysters) or by running byssal threads for security (mussels). Some can bore into rock, wood, or coral.
The cephalopods are voracious predators specialized for locomotion. This group includes the octopuses, squids, and cuttlefish. Most are agile swimmers. Their shell is found internally or lost completely. The name cephalopod means "head-footed". The head has arms with suckers to capture prey. They have large eyes that are amazingly like ours.
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Last Updated 04/06/04- Questions and comments concerning this page may be directed to Marty Daniel.