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A to Z of marine invertebrates

Barnacles are types of crustacean. They attach their shells permanently to rocks or other surfaces. From their shells, their...Read More >>Barnacles are types of crustacean. They attach their shells permanently to rocks or other surfaces. From their shells, their feathery legs reach out into the water to gather in particles of food. When they are exposed to the air at low tide, the barnacles slide plates across the openings to their shells. This prevents them from drying out and stops predators getting in.The oceans are home to a wide range of invertebrate animals. Unlike fish, mammals or reptiles, for example, these animals do not have backbones. They include crustaceans, such as crabs, lobsters and shrimps, which have hard outer parts for protection, and molluscs, which have soft bodies, often protected by shells. Crustaceans and molluscs are sometimes grouped together and called “shellfish”.



Clams with their siphons extended. The creatures use them to take in water and get rid of waste.

Bivalves

Bivalves are kinds of mollusc. They have flat bodies contained inside a shell that has two hinged parts. Clams, cockles, oysters, scallops and mussels are all bivalves. To protect themselves from predators, some bivalves bury themselves in the sand or mud. Others, including scallops, swim away from danger, while oysters and mussels remain permanently attached to rocks. To ensure they stay moist when they are out of the water at low tide, they keep their shells tightly shut.

Among the marine invertebrates is one of the largest animals on Earth: the colossal squid, which may grow up to 14 metres (46 feet) long.

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