Purpose of Shells of Bivalves
Many beach-goers can attest to the beauty of seashells strewn across the sand, but these shells have functions that extend far beyond their beauty. The rounded halves that are usually found separately on the beach, when joined, served important purposes in the lives of sea animals known as bivalves.
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Identification
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Different bivalve species vary in color and size. According to the Water Encyclopedia, there are over 15,000 bivalve species alive in the world today. One purpose of a bivalve's shell, from a scientific point of view, is to provide physical clues for the classification of different species. Variations in shell size, shape and symmetry are all identifying markers that help differentiate between species.
Age
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The clam's age can be determined by its rings. Just as physical characteristics help to identify different species, size variations among like species provide information about the bivalve's age. Bivalve shells are secreted by the mantle, the thin wall that surrounds the interior body. As the animal grows older, the mantle secretions form growth rings, and the bivalve shell becomes larger.
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Defense
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The two shells of the bivalve are joined together with a hinge, forming an exoskeleton that defends the animal's soft inner body. Powerful muscles squeeze the two shells tightly together around the body, and the hard exterior protects against predators.
Swimming
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Though most adult bivalves are unable to swim, there are a few species that can. Scallops are able to move themselves through the water by clamping their shells together fast enough to create a small current of water that propels them forward.
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References
- Photo Credit giant atlantic cockle shell image by Carpenter from Fotolia.com shells image by Stanislav Komogorov from Fotolia.com clam image by bedecs from Fotolia.com
