| There are around 50,000 species of mollusks, ranging from tiny snails less than 1 cm (0.25 in) in length to giant squids, which reach a length of 18 m (60 ft). Despite this great variation in size, most mollusks have the same basic body structure. Most mollusks have a glandular body covering, called the mantle. In some mollusks, such as clams and snails, the mantle secretes a hard shell. Most mollusks have a large muscular organ, called the foot, which is used for burrowing or for moving over the ground or sea bottom. Many mollusks feed by means of the radula, a flexible organ that bears many sharp teeth. Mollusks use gills to absorb nutrients from water and release waste products from cells. |
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