Monday, March 28, 2011

About Mollusks

The mollusks or molluscs according to American spelling and British spelling respectively are the second largest phylum, Mollusca of invertebrates after Arthropods. The molluscs are well-known for their decorative shells or as seafood. These mollusks consist of octopus, clams, snails, abalone, cuttlefish, and squid. The 50,000 species of mollusks are known to the human being.
In more simple words it can be said that a mollusk is another name for a shellfish. There are three groupings of shellfish. They are as follows:

Hatchet-footed - These live inside the two shells that are joined by a muscular hinge, which can close and open the shell. These are called as bivalves. The age of the mollusks is known by its lines on the shell. As the shell gets bigger, the shellfish gets older. Some of the examples of bivalves are clams, scallops, mussels and oysters.
Belly-footed - These species has just one spiral shell. They carry their shells on their backs and are called univalves. Some of the examples of this group are the snail, slug, conch and periwinkle.
Head-footed – These species are known as head-footed as they have a definite head surrounded by tentacles. The two of the species in this group are squid and octopus

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