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The sensory organs of bivalves are largely located on the posterior mantle margins. The organs are usually mechanoreceptors or chemoreceptors , in some cases located on short tentacles . The osphradium is a patch of sensory cells located below the posterior adductor muscle that may serve to taste the water or measure its turbidity .
The internal anatomy is visible, including the paired siphons to the right A siphon is an anatomical structure which is part of the body of aquatic molluscs in three classes : Gastropoda , Bivalvia and Cephalopoda (members of these classes include saltwater and freshwater snails , clams , octopus , squid and relatives).
Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue. Bones come in a variety of shapes and have a complex internal and external structure.
The main body cavity is a hemocoel through which blood circulates; as such, their circulatory systems are mainly open. The "generalized" mollusc's feeding system consists of a rasping "tongue", the radula, and a complex digestive system in which exuded mucus and microscopic, muscle-powered "hairs" called cilia play various
In fish, the system has only one circuit, with the blood being pumped through the capillaries of the gills and on to the capillaries of the body tissues. This is known as single cycle circulation. The heart of fish is therefore only a single pump (consisting of two chambers). Fish have a closed-loop circulatory system.
In some mollusks the mantle cavity is a brood chamber, and in cephalopods and some bivalves such as scallops, it is a locomotory organ. The mantle is highly muscular. In cephalopods the contraction of the mantle is used to force water through a tubular siphon, the hyponome , and this propels the animal very rapidly through the water.
A bivalve shell is the enveloping exoskeleton or shell of a bivalve mollusc, composed of two hinged halves or valves. The two half-shells, called the "right valve" and "left valve", are joined by a ligament and usually articulate with one another using structures known as "teeth" which are situated along the hinge line .
Certain molluscs, such as the bivalves, [2] possess paired ctenidia, but others, such as members of the Ampullariidae, [3] bear a single ctenidium. [ 4 ] [ 5 ] A ctenidium is shaped like a comb or a feather, with a central part from which many filaments or plate-like structures protrude, lined up in a row.