Types of Shells
Shells come in many shapes and sizes. They can be found along shorelines or in the depths of the ocean. Smaller shells move along with the waves and currents and often wash up on the beach. Each type of shell has unique features that sets it apart from other shells, and each type serves a different purpose.
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Function
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Human bodies have a skeleton to protect the internal organs from damage. Mollusks, a class of marine creatures, have external shells to offer them the same protection. They act as camouflage to hide the mollusks from their predators by offering a hard protective armor that's hard to bite through. The shell also protects the sea creatures from being thrown around by ocean currents and bad weather. They're made from calcium, just like human skeletons.
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Types
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Univalve or gastropods are one-piece, swirl-shaped shells. They do not have hinges and aren't attached together. Bivalve shells are attached to other parts. They have two matching halves, though tides and waves often break them apart. Clams are a type of bivalve mollusk. Some of the most common shells are the spiral-shaped whelks, miniature clam-shaped shells called coquinas, and the long, tube-shaped small jackknife clam.
Size
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The largest univalve shell can grow to be more than 30 inches long, but most univalve shells are much smaller. They are usually less than 8 inches long. The largest bivalve found was almost 5 feet wide. These larger shells can be found in the South Pacific and near the Great Barrier Reef. They're appropriately known as giant clams.
Considerations
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If a shell appears to have a hole in it, the shell likely was attacked by a predator. Certain birds have beaks that will peck through the hard protective shell, allowing the bird to eat the soft mollusk that resides inside. In some cases, an enzyme is released by a predator to enable them to get to the soft creature inside the shell.
Fun Facts
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Hermit crabs wear their shell on their backs. Their shell forms a safe place for them to sleep and live and protects their soft abdomen from predators. When they grow out of their shells, they abandon their original shell and "move" to a larger shell. A clam living in a coquina shell will burrow into the sand to avoid being eaten by seagulls and other predators.
Warning
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Cone shells should not be handled; they contain miniature teeth that are very sharp. They are found in tropical bays, in cracks and crevices and along rocky shores. They can also be found in coral reefs. Coral is very sharp and can slice like a knife, so avoid shelling when around coral reefs.
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Resources
- Photo Credit Image by Flickr.com, courtesy of Leonardo Aguiar
