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:''For other species of cookiecutter sharks, see ''Isistius. Cookiecutter shark (''Isistius brasiliensis''), also called the cigar shark, is a species of small dogfish shark in the family Dalatiidae. This shark occurs in warm, oceanic waters worldwide, particularly near islands, and has been recorded as deep as 3.7 km (2.3 mi). It migrates vertically up to 3 km (1.9 mi) every day, approaching the surface at dusk and descending with the dawn. Reaching only 42–56 cm (17–22 in) in length, the cookiecutter shark has a long, cylindrical body with a short, blunt snout, large eyes, two tiny spineless dorsal fins, and a large caudal fin. It is dark brown in color, with light-emitting photophores covering its underside except for a dark "collar" around its throat and gill slits. The name "cookiecutter shark" refers to its feeding habit of gouging round plugs, as if cut out with a cookie cutter, out of larger animals. Marks made by cookiecutter sharks have been found on a wide variety of marine mammals and fishes, as well as on submarines, undersea cables, and even human bodies. It also consumes whole smaller prey such as squid. Cookiecutter sharks have adaptations for hovering in the water column and likely rely on stealth and subterfuge to capture more active prey. Its dark collar seems to mimic the silhouette of a small fish, while the rest of its body blends into the downwelling light via its ventral photophores. When a would-be predator approaches the lure, the shark attaches itself using its suctorial lips and specialized pharynx and neatly excises a chunk of flesh using its bandsaw-like set of lower teeth. This species has been known to travel in schools. Though rarely encountered because of its oceanic habitat, a handful of documented attacks on humans were apparently caused by cookiecutter sharks. Nevertheless, this diminutive shark is not regarded as highly dangerous. The International Union for Conservation of Nature (IUCN) has listed the cookiecutter shark under Least Concern, as it is widely distributed, has no commercial value, and is not particularly susceptible to fisheries. ==Taxonomy== French naturalists Jean René Constant Quoy and Joseph Paul Gaimard originally described the cookiecutter shark during the 1817–1820 exploratory voyage of the corvette ''Uranie'' under Louis de Freycinet, giving it the name ''Scymnus brasiliensis'' because the type specimen was caught off Brazil. In 1824, their account was published as part of ''Voyage autour du monde...sur les corvettes de S.M. l'Uranie et la Physicienne'', Louis de Freycinet's 13-volume report on the voyage. In 1865, American ichthyologist Theodore Nicholas Gill coined the new genus ''Isistius'' for this species, after Isis, the Egyptian goddess of light.〔Bester, C. (Biological Profiles: Cookiecutter Shark ). Florida Museum of Natural History Ichthyology Department. Retrieved on January 26, 2010.〕 One of the earliest accounts of the wounds left by the cookiecutter shark on various animals is in ancient Samoan legend, which held that ''atu'' (skipjack tuna) entering Palauli Bay would leave behind pieces of their flesh as a sacrifice to Tautunu, the community chief. In later centuries, various other explanations for the wounds were advanced, including lampreys, bacteria, and invertebrate parasites.〔 In 1971, Everet Jones of the U.S. Bureau of Commercial Fisheries (a predecessor of the National Marine Fisheries Service) discovered the cigar shark, as it was then generally known, was responsible. Shark expert Stewart Springer thus popularized the name "cookiecutter shark" for this species (though he originally called them "demon whale-biters"). Other common names used for this shark include luminous shark, smalltooth cookiecutter shark, and smooth cookiecutter shark. 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「Cookiecutter shark」の詳細全文を読む スポンサード リンク
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