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Middle Miocene to Present | image = Alopias superciliosus.jpg | image_width = 240px | status = VU | status_system = iucn3.1 | status_ref = | regnum = Animalia | phylum = Chordata | classis = Chondrichthyes | subclassis = Elasmobranchii | superordo = Selachimorpha | ordo = Lamniformes | familia = Alopiidae | genus = ''Alopias'' | species = ''A. superciliosus'' | range_map = Bigeye Thresher.png | range_map_width = 240px | range_map_caption = Range of the bigeye thresher | binomial = ''Alopias superciliosus'' | binomial_authority = (R. T. Lowe, 1840) | synonyms = ''Alopecias superciliosus'' R. T. Lowe, 1840 ''Alopias profundus'' Nakamura, 1935 }} The bigeye thresher (''Alopias superciliosus'') is a species of thresher shark, family Alopiidae, found in temperate and tropical oceans worldwide. Like other thresher sharks, nearly half its total length consists of the elongated upper lobe of the tail fin. Its common name comes from its enormous eyes, which are placed in keyhole-shaped sockets that allow them to be rotated upward. This species can also be distinguished by a pair of deep grooves on the top of its head, from which its scientific name is derived. The large eyes of the bigeye thresher are adapted for hunting in low light conditions. It is one of the few sharks that conduct a diel vertical migration, staying in deep water during the day and moving into surface waters at night to feed. To protect its sensitive brain and eyes from the temperature changes accompanying these movements, the bigeye thresher has a vascular exchange system called the rete mirabile around those organs. This species feeds mainly on fish and squid, which are stunned via whip-like strikes of the long tail. Bigeye threshers are ovoviviparous, usually bearing litters of two pups. The embryos are oophagous and feed on ova produced by the mother while inside the uterus. This shark is caught by commercial fisheries across its range; the meat is not highly regarded but the skin, fins, and liver oil are valued. It has been assessed as Vulnerable by the International Union for Conservation of Nature (IUCN). ==Taxonomy and phylogeny== British biologist Richard Thomas Lowe was the first to scientifically describe the bigeye thresher, in papers published in ''Proceedings of the Royal Society of London'' (1840) and ''Transactions of the Zoological Society of London'' (1849, sometimes given as 1839). He based his description on a specimen caught off Madeira in the eastern Atlantic Ocean.〔 However, Lowe's description was subsequently overlooked by researchers and this species was known by different names until the 1940s, when new specimens from Cuba and Florida prompted its original scientific name to be resurrected. The specific epithet ''superciliosus'' is from the Latin ''super'' meaning "above", and ''ciliosus'' meaning "eyebrow", referring to the distinct lateral grooves above the eyes.〔Jensen, C. (Bigeye Thresher ). ''Florida Museum of Natural History''. Retrieved on December 21, 2008.〕 An allozyme analysis conducted by Blaise Eitner in 1995 showed that the closest relative of the bigeye thresher is the pelagic thresher (''A. pelagicus''), with which it forms a clade. Fossil remains of the bigeye thresher dating to the Middle Miocene (16.0–11.6 Ma) have been found in the Hokuriku region of Japan.〔 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「Bigeye thresher」の詳細全文を読む スポンサード リンク
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