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Class - Bivalvia (Clams, Oysters, Mussels and Scallops)

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Class - Bivalvia (Clams, Oysters, Mussels and Scallops)

The Bivalves

Bivalves include clams, oytsters, mussels and scallops.

Habitat: They are found in both salt (marine) and freshwater habitats.

Physical Traits: They have two shells connected by a hinge – called the ligament, and kept closed by powerful muscles. The shells can open and close when needed, but are usually held closed by powerful muscles to protect them from predators.  All use their muscular foot to meet their different lifestyle needs. Clams burrow into the sandy bottom. Scallops burrow or swim freely, using their shell to “clap” water propelling them as needed. Mussels use their foot to anchor to rocks and other objects. They have gills that are bathed with fresh water (and oxygen) through posterior siphons. They have no head, but a diffuse nerve network made up of three nerve centers (or ganglia) distributed around their visceral mass.

Diet: Unlike many mollusks that feed using a rasping tongue, called a radula, bivalves feed by filtering food particles from the water. They do this by siphoning water over the gills which traps it and propels it toward the mouth.

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Class - Bivalvia (Clams, Oysters, Mussels and Scallops)
Clams

Range and Habitat 

They are found in temperate oceans throughout the world in both salt (marine) and freshwater habitats.

Body Traits  

They have two shells connected by a hinge – called the ligament and kept closed by powerful  muscles. The shells can open and close when needed, but are usually held closed by powerful muscles to protect them from predators.  All use their muscular foot to meet their different lifestyle needs. They have no head, but a diffuse nerve network made up of three nerve centers (or ganglia) distributed around their visceral mass.

Habits  

Clams burrow into the sandy bottom. Scallops burrow or swim freely, using their shell to “clap” water propelling them as needed. Mussels use their foot to anchor to rocks and other objects. They have gills that are bathed with fresh water (and oxygen) through posterior siphons.

Diet  

Unlike many mollusks that feed using a rasping tongue, called a radula, bivalves feed by filtering food particles from the water. They do this by siphoning water over the gills which traps it and propels it toward the mouth.

Class - Bivalvia (Clams, Oysters, Mussels and Scallops)
Mussel (California)
Mytilus californianus

Range and Habitat

They are found on the Pacific coast of North America, from Alaska to Mexico living on rocks and pier pilings in tide pools that are sometimes wet and sometimes dry (middle intertidal zone).

Body Traits  

They are blackish-blue with darker edges. They have growth rings and white blotches. They are about 5 inches long (130 mm).

Habits  

They gather in huge beds, sometimes many layers thick. They attach to surfaces with fine fiber threads from their muscular “foot” that send out a glue that sticks them fast to where they are. Big waves can tear off mussels and star fish feed on them.

Diet  

They open their shells just a bit at high tide to feed. They feed by pulling seawater through their shells and filtering out plankton in their gills to feed on.

Reproduction  

Males and females send out “broadcast” sperm or eggs into the water where fertilization occurs.

Class - Bivalvia (Clams, Oysters, Mussels and Scallops)

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