Life in the Sea - Shell Fish

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Shell fish include crustaceans (crabs and lobsters) and mollusks (clams and oysters). Mollusks were among the first inhabitants of the Earth. Fossils of mollusks have been found in rocks and date back over 500 million years. These fossils are usually well-preserved because of the mollusks' hard shell.

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Crabs and Lobsters

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Crabs and Lobsters
Crustaceans live mostly in the ocean or other waters. Most commonly known crustaceans are the crab, lobster and barnacle.

Crustaceans have a hard, external shell which protects their body. Crustaceans have a head and abdomen. The head has antennae which are part of their sensory system. The abdomen includes the heart, digestive system and reproductive system.

The abdomen also has appendages, such as legs, for crawling and swimming. Many crustaceans also have claws that help with crawling and eating.

Clams and Oysters

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Most mollusks have a soft, skin-like organ covered with a hard outside shell. Some mollusks live on land, such as the snail and slug. Other mollusks live in water, such as the oyster, mussel, clam, squid and octopus.

Land living mollusks, like the snail, move slowly on a flat sole called a foot.

Ocean living mollusks move or swim by jet propulsion. They propel themselves by ejecting water from their body. For example, the squid ejects a jet of water from a cavity within its body, and the scallop ejects water to move by clamping its shell closed.

Sea Snail
Other ocean living mollusks, like the oyster, attach themselves to rocks or other surfaces, and can't move. They feed by filtering small food particles from water that flows through them.


Books on Shell Fish

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Other links on Shell Fish

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All About Lobsters http://octopus.gma.org/lobsters/allaboutlobsters
Hermit Crab http://www.cap.nsw.edu.au/bb_site_intro/

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