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A cockle is a small, edible, saltwater clam, a marine bivalve mollusc. Although many small edible bivalves are loosely called cockles, true cockles are species in the family Cardiidae. True cockles live in sandy, sheltered beaches throughout the world. The distinctive rounded shells are bilaterally symmetrical, and are heart-shaped when viewed from the end. Numerous radial evenly spaced ribs are a feature of the shell in most but not all genera (for an exception, see the genus ''Laevicardium'', the egg cockles, which have very smooth shells). The shell of a cockle is able to close completely (i.e., there is no "gape" at any point around the edge). Though the shell of a cockle may superficially resemble that of a scallop because of the ribs, cockles can be distinguished from scallops morphologically in that cockle shells lack "auricles" (triangular ear-shaped protrusions near the hinge line) and scallop shells lack a pallial sinus. Behaviorally, cockles live buried in sediment, whereas scallops are either free-living and will swim in the sea water to avoid a predator, or in some cases they live attached by a byssus to a substrate. The mantle has three apertures (inhalant, exhalant, and pedal) for siphoning water and for the foot to protrude. Cockles typically burrow using the foot, and feed by filtering plankton from the surrounding water. Cockles are capable of "jumping" by bending and straightening the foot. As is the case in many bivalves, cockles display gonochorism (the sex of an individual varies according to conditions),〔(【引用サイトリンク】title=Synthesis on biology of Common European Cockle (Cerastoderma edule )〕 and some species reach maturity rapidly. The common name "cockle" is also given by seafood sellers to a number of other small, edible marine bivalves which have a somewhat similar shape and sculpture, but are in other families such as the Veneridae (Venus clams) and the Arcidae (ark clams). Cockles in the family Cardiidae are sometimes referred to as "true cockles" to distinguish them from these other species. ==Species== There are more than 200 living species of cockles, with many more fossil forms.〔(【引用サイトリンク】title=Cardiidae (Cockles) )〕 The common cockle, ''Cerastoderma edule'', is widely distributed around the coastlines of Northern Europe, with a range extending west to Ireland, the Barents Sea in the north, Norway in the east, and as far south as Senegal. The dog cockle, ''Glycymeris glycymeris'', has a similar range and habitat to the common cockle, but is not at all closely related, being in the family Glycymerididae. The dog cockle is edible, but due to its toughness when cooked it is generally not eaten, although a process is being developed to solve this problem. The blood cockle, ''Anadara granosa'' (not related to the true cockles, instead in the family Arcidae) is extensively cultured from southern Korea to Malaysia.〔(【引用サイトリンク】title=Status of mollusc culture in selected Asian countries )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cockle (bivalve)」の詳細全文を読む スポンサード リンク
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