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The whitetip reef shark (''Triaenodon obesus'') is a species of requiem shark, in the family Carcharhinidae, and the only member of its genus. A small shark usually not exceeding in length, this species is easily recognizable by its slender body and short but broad head, as well as tubular skin flaps beside the nostrils, oval eyes with vertical pupils, and white-tipped dorsal and caudal fins. One of the most common sharks found on Indo-Pacific coral reefs, the whitetip reef shark occurs as far west as South Africa and as far east as Central America. It is typically found on or near the bottom in clear water, at a depth of . During the day, whitetip reef sharks spend much of their time resting inside caves. Unlike other requiem sharks, which rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its gills and lie still on the bottom. At night, whitetip reef sharks emerge to hunt bony fishes, crustaceans, and octopus in groups, their elongate bodies allowing them to force their way into crevices and holes to extract hidden prey. Individuals may stay within a particular area of the reef for months to years, time and again returning to the same shelter. This species is viviparous, in which the developing embryos are sustained by a placental connection to their mother. One of the few sharks in which mating has been observed in the wild, receptive female whitetip reef sharks are followed by prospective males, which attempt to grasp her pectoral fin and maneuver the two of them into positions suitable for copulation. Females give birth to one to six pups every other year, after a gestation period of 10–13 months. Whitetip reef sharks are rarely aggressive towards humans, though they may investigate swimmers closely. However, spear fishers are at risk of being bitten by one attempting to steal their catch. This species is caught for food, though ciguatera poisoning resulting from its consumption has been reported. The IUCN has assessed the whitetip reef shark as Near Threatened, noting its numbers are dwindling due to increasing levels of unregulated fishing activity across its range. The slow reproductive rate and limited habitat preferences of this species renders its populations vulnerable to overfishing. ==Taxonomy and phylogeny== The whitetip reef shark was first described by the German naturalist Eduard Rüppell as ''Carcharias obesus'', in the 1837 ''Fische des Rothen Meeres'' (''Fishes of the Red Sea''). His choice of the specific epithet ''obesus'' was curious, given that this shark is actually quite slender. Later in 1837, Johannes Müller and Friedrich Henle moved this species into its own genus ''Triaenodon'', from the Greek ''triaena'' meaning "trident", and ''odon'' meaning "tooth". As Rüppell did not originally designate a holotype, in 1960 a 31-cm-long specimen caught off Jeddah, Saudi Arabia, was made the species lectotype.〔 Other common names for this shark include blunthead shark, light-tip shark, reef whitetip shark, and whitetip shark. Once placed in the family Triakidae, the whitetip reef shark is now recognized by most authors as belonging to the family Carcharhinidae on the basis of morphological characters, such as a full nictitating membrane, well-developed precaudal pit, strong lower caudal fin lobe, and scroll-like intestinal valves.〔 Morphological and molecular phylogenetic analyses suggest the whitetip reef shark is grouped with the lemon sharks (''Negaprion'') and the sliteye shark (''Loxodon'') in occupying an intermediate position on the carcharhinid evolutionary tree, between most basal genera (''Galeocerdo'', ''Rhizoprionodon'', and ''Scoliodon'') and the most derived (''Carcharhinus'' and ''Sphyrna''). 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「Whitetip reef shark」の詳細全文を読む スポンサード リンク
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