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River stingrays or freshwater stingrays are Neotropical freshwater fishes of the Potamotrygonidae family (order Myliobatiformes). They are native to northern, central and eastern South America, living in rivers that drain into the Caribbean, and into the Atlantic as far south as the Río de la Plata in Argentina. Generally, each species is native to a single river basin, and the greatest species richness can be found in the Amazon. River stingrays are almost circular in shape, and range in size from ''Potamotrygon schuhmacheri'', which reaches in diameter, to the short-tailed river stingray, ''P. brachyura'', which grows up to in diameter. The upper surface is covered with denticles (sharp tooth-like scales). Most species are brownish or greyish and often have distinctive spotted or mottled patterns, but a few species are largely blackish with contrasting white spots. They have a venomous caudal sting, and are one of the most feared freshwater fishes in the Neotropical region, sometimes more feared than piranhas and electric eels. However, they are not dangerous unless stepped on or otherwise threatened. River stingrays are the only family of batoids completely restricted to fresh water habitats.〔Compagno, L. J. V. & S. F. Cook (1995) "The exploitation and conservation of freshwater elasmobranchs: status of taxa and prospects for the future". In: ''The Biology of Freshwater Elasmobranchs''. Oetinger, M. I. & Zorzi, G. D. (eds.). ''Journal of Aquariculture & Aquatic Sciences'', 7: 62–90.〕〔(Freshwater Stingrays (Potamotrygonidae): status, conservation and management challenges ) CITES. AC20 Inf. 8.〕 While there are true freshwater species in the family Dasyatidae, for example ''Himantura chaophraya'', the majority of species in this family are saltwater fish. ==Species== The taxonomy of the river stingrays is complex and undescribed species remain. * Genus ''Heliotrygon'' Carvalho & Lovejoy, 2011 * * ''Heliotrygon gomesi'' Carvalho & Lovejoy, 2011 (Gomes's round ray) * * ''Heliotrygon rosai'' Carvalho & Lovejoy, 2011 (Rosa’s round ray) * Genus ''Paratrygon'' A. H. A. Duméril, 1865 * * ''Paratrygon aiereba'' Walbaum, 1792 (Discus ray) * Genus ''Plesiotrygon'' Rosa, Castello & Thorson, 1987 * * ''Plesiotrygon iwamae'' Rosa, Castello & Thorson, 1987 (Long-tailed river stingray) * * ''Plesiotrygon nana'' Carvalho & Ragno, 2011 (Black-tailed antenna ray) * Genus ''Potamotrygon'' Garman, 1877 * * ''Potamotrygon amandae'' Loboda & M. R. de Carvalho, 2013 * * ''Potamotrygon boesemani'' Rosa, M. R. de Carvalho & Almeida Wanderley, 2008 (Emperor ray) * * ''Potamotrygon brachyura'' (Günther, 1880) (Short-tailed river stingray) * * ''Potamotrygon constellata'' (Vaillant, 1880) (Thorny river stingray) * * ''Potamotrygon falkneri'' Castex & Maciel, 1963 (Largespot river stingray) * * ''Potamotrygon henlei'' (Castelnau, 1855) (Bigtooth river stingray) * * ''Potamotrygon humerosa'' Garman, 1913 * * ''Potamotrygon hystrix'' (J. P. Müller & Henle, 1834) (Porcupine river stingray) * * ''Potamotrygon leopoldi'' Castex & Castello, 1970 (White-blotched river stingray) * * ''Potamotrygon limai'' Fontenelle, J. P. C. B. da Silva & M. R. de Carvalho, 2014〔Fontenelle, J.P., Da Silva, J.P.C.B. & De Carvalho, M.R. (2014): ''Potamotrygon limai'', sp. nov., a new species of freshwater stingray from the upper Madeira River system, Amazon basin (Chondrichthyes: Potamotrygonidae). ''Zootaxa, 3765 (3): 249–268.''〕 * * ''Potamotrygon magdalenae'' (A. H. A. Duméril, 1865) (Magdalena river stingray) * * ''Potamotrygon marinae'' Deynat, 2006 * * ''Potamotrygon motoro'' (J. P. Müller & Henle, 1841) (Ocellate river stingray) * * ''Potamotrygon ocellata'' (Engelhardt, 1912) (Red-blotched river stingray) * * ''Potamotrygon orbignyi'' (Castelnau, 1855) (Smoothback river stingray) * * ''Potamotrygon pantanensis'' Loboda & M. R. de Carvalho, 2013〔 * * ''Potamotrygon schroederi'' Fernández-Yépez, 1958 (Rosette river stingray) * * ''Potamotrygon schuhmacheri'' Castex, 1964 (Parana River stingray) * * ''Potamotrygon scobina'' Garman, 1913 (Raspy river stingray) * * ''Potamotrygon signata'' Garman, 1913 (Parnaiba River stingray) * * ''Potamotrygon tatianae'' J. P. C. B. da Silva & M. R. de Carvalho, 2011 * * ''Potamotrygon tigrina'' M. R. de Carvalho, Sabaj Pérez & Lovejoy, 2011 (Tiger ray) * * ''Potamotrygon yepezi'' Castex & Castello, 1970 (Maracaibo River stingray) 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「Potamotrygonidae」の詳細全文を読む スポンサード リンク
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