Corrections? Bivalves include clams, oysters, mussels, scallops, and numerous other families of shells. Marine members of the Bivalvia class are molluscs that have laterally flattened bodies enclosed by a shell formed of two hinged parts. Terms in this set (11) Key Characteristics. Bivalve, (class Bivalvia), any of more than 15,000 species of clams, oysters, mussels, scallops, and other members of the phylum Mollusca characterized by a shell that is divided from front to back into left and right valves. Scallops, Clams, oysters, mussels. 271). B. Of these, 21 have…, A clamshell is an example of a simple system in which a rigid skeleton is worked by muscles. Feeding type(s): mostly suspension feeders; some deposit feeders and carnivores Geological range: Cambrian to today. The stomach of a bivalve is positioned in the dorsal portion of the visceral mass, surrounded by the digestive gland composed of the rami of the digestive diverticula ( Figure 19.19 ). More than 15,000 living species of bivalves are known, of which about 500 live in fresh water; the others occur in all seas. NO RADULA laterally compressed bodies shell composed of two valves large mantle cavity well developed gills. Bivalves thus occur at all latitudes and depths, although none are planktonic. Throughout history, bivalves have been one of the most important marine animals to humans. The donax clam (Donax), also known as the coquina clam, is also commonly eaten in broth or chowder. Gravity. Bivalvia | Bivalves. M. campechiensis, the southern quahog, is about 7.5 to 15 cm long and has a heavy, white, plump shell. A bivalve is an animal belonging to the class Bivalvia. By the Middle Ordovician period (about 460 mya), recognizable members of all modern subclasses had appeared. Please select which sections you would like to print: Corrections? The northern coquina (D. fossor), 6 to 12 mm long, is yellowish white with bluish rays and inhabits shallow waters from Long Island to Cape May, New Jersey. They rarely travel over the bottom as do some other bivalves. In keeping with a largely sedentary and deposit-feeding or suspension-feeding lifestyle, bivalves have lost the head and the radular rasping organ typical of most mollusks. The shell morphology and hinge structure are used in classification. Updates? a class of marine and freshwater molluscs with laterally compressed bodies enclosed by a shell in two hinged parts. Members of the class Bivalvia are … They occur in all aquatic habitats, however by far the majority of species are marine. By limiting shell thickness (which reduces weight), smoothing the shell contours (which reduces drag), and assuming an aerofoil-like leading edge, such scallops can awkwardly swim several metres at a time. Bivalves are aquatic animals, and different species of bivalve… Lives life upsidedown reduced head mouth surrounded by palps muscular foot for burrowing … Professor of Ecology and Biodiversity; Director, Swire Institute of Marine Science, University of Hong Kong. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. You likely know them as shellfish. All 15,000 known species of bivalves are aquatic in nature, with close to 80% being marine (saltwater environments). ohaneze ndi-igbo, new york chapter. All bivalves are aquatic, living at all depths of the sea and in brackish waters and freshwaters . They can be closed to protect the animal within or allowed to open. It is 15 to 20 cm in length, has a white, oblong shell, and may weigh as much as 3.6 kg (8 pounds). The byssus is a larval feature that is retained by adults of some bivalve groups, such as the true mussels (family Mytilidae) of marine and estuarine shores and the family Dreissenidae of fresh and estuarine waters. (b) A giant clam. A few clams, such as the gem clam (Gemma), have internal fertilization and development. The rasping tongue, the radula, is present in which molluscan group? Primitive bivalves ingest sediment; however, in most species…, Terrestrial ecosystems are far from being the only places where recent extinctions have occurred. The taxonomic term Bivalvia was first used by Linnaeus in the 10th edition of his Systema Naturae in 1758 to refer to animals having shells composed of two valves. Other bivalves have used the byssus to attach securely within crevices and thus to assume a laterally flattened, circular shape. In other species, such as the clams, the foot has become modified for rapid and effective digging, and the folds of the mantle tissue have developed into long siphons. The eggs develop into larvae that swim briefly before settling permanently on the bottom. The shell is dirty white, oval, and 7.5 to 15 cm long. PLAY. This form has allowed the close attachment of one valve to a hard surface, and although some groups still retain byssal attachment (family Anomiidae), others have forsaken this for cementation, as in the true oysters (family Ostreidae), where the left valve is cemented to estuarine hard surfaces. However this is the main article for the class Bivalvia and this classification differs from previous classifications in the placement of taxa and provides information unlikely to be included elsewhere in Wikipedia. Common names of representatives: clams, scallops, oysters, mussels. Bivalvia is a class of marine and freshwater molluscs with laterally compressed bodies enclosed by a shell in two hinged parts. Bivalve shell and body form is thus intimately related to habitat and the relative degree of exposure to predation. Such a shell form and habit evolved first within sediments (endobyssate), where the byssus serves for anchorage and protection when formed into an enclosing nest. Get exclusive access to content from our 1768 First Edition with your subscription. (a) A species of sea scallop. Most clams inhabit shallow waters, in which they are generally protected from wave action by the surrounding bottom. These are the scientists who first described the taxon and so should be retained where they are. The valves are connected to one another at a hinge. Members of the molluscan class Bivalvia (formerly, Pelecypoda) are known commonly as bivalves and include clams, oysters, mussels, and scallops. 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