Bivalve

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Various bivalves

Bivalvia is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. Bivalves include clams, oysters, mussels, scallops, and numerous other families that live in saltwater or freshwater. The class is also known as Pelecypoda or Lamellibranchia.

Anatomy

Bivalves have a shell composed of two parts, or valves, that are typically mirror images of each other. The shell is made of calcium carbonate and is secreted by the mantle. The two valves are joined together by a ligament and are closed by one or two adductor muscles. The interior of the shell is lined with a layer of tissue called the mantle, which secretes the shell material.

Habitat

Bivalves can be found in a variety of aquatic environments, from the deep sea to freshwater rivers and lakes. They are often found buried in sediment, attached to hard surfaces, or free-living on the sea floor. Some species, such as oysters and mussels, form large colonies known as beds or reefs.

Feeding

Most bivalves are filter feeders, using their gills to extract plankton and other small particles from the water. The gills are covered with cilia that create a current, drawing water into the shell and over the gills. Food particles are trapped in mucus on the gills and transported to the mouth.

Reproduction

Bivalves have a variety of reproductive strategies. Some species are hermaphroditic, while others have separate sexes. Fertilization can be internal or external, depending on the species. Many bivalves release their eggs and sperm into the water column, where fertilization occurs. The resulting larvae are planktonic and undergo several stages of development before settling to the bottom and metamorphosing into juvenile bivalves.

Importance

Bivalves play a significant role in aquatic ecosystems as filter feeders, helping to maintain water quality by removing suspended particles. They are also an important food source for many animals, including humans. Bivalves such as oysters and mussels are cultivated for food, and their shells are used in various industries.

Conservation

Many bivalve species are threatened by habitat loss, pollution, and overfishing. Conservation efforts include habitat restoration, pollution control, and the establishment of protected areas. Sustainable aquaculture practices are also being developed to reduce the impact on wild populations.

See also

• Mollusca
• Gastropoda
• Cephalopoda
• Scaphopoda
• Polyplacophora