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''Euastacus'' is a genus of freshwater crayfish known as "spiny crayfish". They are found in the south-east of the Australian mainland, along with another genus of crayfish, ''Cherax''. Both genera are members of the Parastacidae family, a family of freshwater crayfish restricted to the Southern Hemisphere. ''Euastacus'' crayfish are distinguished from the smooth-shelled ''Cherax'' species by the short robust spikes on their claws and carapace, and frequently, their larger size. Many ''Euastacus'' species grow to a relatively large size, with the Murray River crayfish (''Euastacus armatus'') being the second largest freshwater crayfish species in the world. (The largest freshwater crayfish in the world is Tasmanian giant freshwater crayfish (''Astacopsis gouldi''), found on the Australian island of Tasmania, and the ''Astacopsis'' genus is now known to be a very closely related sister genus to ''Euastacus''.) The genera ''Cherax'' and ''Euastacus'' continue a trend present in many Australian native freshwater fish genera of speciation into generalist lowland and specialist upland species. Generally, ''Cherax'' species inhabit lowland rivers at low to medium altitudes and swamps and ephemeral waters in inland areas of Australia including the Murray-Darling Basin. Conversely, ''Euastacus'' species are only found in permanent waters and generally inhabit upland rivers at medium to high altitudes in the Murray-Darling Basin as well as many easterly and southerly flowing coastal river systems. The partial exceptions to this are: * the Murray River crayfish which was originally found along the entire length of the Murray River in addition to many upland habitats, and is still found in the middle reaches of the Murray River * the Glenelg Spiny Crayfish (''Eustacus bispinosus''), found (or formerly found) in lowland areas of the Glenelg River system and Eight Mile Creek/Ewen Ponds system * the Gippsland Crayfish (''Euastacus kershawi''), found in lowland areas of some streams in the Gippsland area. Even when found in lowland habitats, these several more adaptable ''Euastacus'' crayfish are still highly dependent on reliable flows and good water quality, with good dissolved oxygen levels and low salinity. In contrast to ''Cherax'' (yabby) species, Euastacus species are unable to survive drying of their habitats. The genus ''Cherax'' has a far wider distribution than the ''Euastacus'' genus, and is found in many parts of Australia including south-western Australia. The ''Euastacus'' genus is restricted to the south-east of the Australian mainland. There is a high degree of endemism in ''Euastacus'' species in coastal river systems, with many species restricted to single river or creek catchment. ''Euastacus'' species occur in several upland reservoirs. ==Species== Of the 50 species in the genus ''Euastacus'', 17 are on the IUCN Red List as critically endangered (CR), 17 are endangered (EN), 5 vulnerable (VU), 1 near threatened (NT), 8 least concern (LC) and 1 is data deficient (DD): *''Euastacus armatus'' (Von Martens, 1866) *''Euastacus australasiensis'' (H. Milne-Edwards, 1837) *''Euastacus balanesis'' Morgan, 1988 *''Euastacus bidawalis'' Morgan, 1986 *''Euastacus bindal'' Morgan, 1989 *''Euastacus bispinosus'' Clark, 1936 *''Euastacus brachythorax'' Riek, 1969 *''Euastacus clarkae'' Morgan, 1997 *''Euastacus claytoni'' Riek, 1969 *''Euastacus crassus'' Riek, 1969 *''Euastacus dalagarbe'' Coughran, 2005 *''Euastacus dangadi'' Morgan, 1997 *''Euastacus diharawalus'' Morgan, 1997 *''Euastacus diversus'' Riek, 1969 *''Euastacus eungella'' Morgan, 1988 *''Euastacus fleckeri'' (Watson, 1953) *''Euastacus gamilaroi'' Morgan, 1997 *''Euastacus girurmulayn'' Coughran, 2005 *''Euastacus gumar'' Morgan, 1997 *''Euastacus guruhgi'' Coughran, 2005 *''Euastacus guwinus'' Morgan, 1997 *''Euastacus hirsutus'' (McCulloch, 1917) *''Euastacus hystricosus'' Riek, 1951 *''Euastacus jagabar'' Coughran, 2005 *''Euastacus jagara'' Morgan, 1988 *''Euastacus kershawi'' Smith, 1912 *''Euastacus maccai'' McCormack & Coughran, 2008 *''Euastacus maidae'' (Riek, 1956) *''Euastacus mirangudjin'' Coughran, 2002 *''Euastacus monteithorum'' Morgan, 1989 *''Euastacus morgani'' Coughran & McCormack, 2011 *''Euastacus neodiversus'' Riek, 1969 *''Euastacus neohirsutus'' Riek, 1956 *''Euastacus pilosus'' Coughran & Leckie, 2007 *''Euastacus polysetosus'' Riek, 1951 *''Euastacus reductus'' Riek, 1969 *''Euastacus rieki'' Morgan, 1997 *''Euastacus robertsi'' Monroe, 1977 *''Euastacus setosus'' (Riek, 1956) *''Euastacus simplex'' Riek, 1956 *''Euastacus spinichelatus'' Morgan, 1997 *''Euastacus spinifer'' (Heller, 1865) *''Euastacus sulcatus'' Riek, 1951 *''Euastacus suttoni'' Clark, 1941 *''Euastacus urospinosus'' (Riek, 1956) *''Euastacus valentulus'' Riek, 1951 *''Euastacus wiowuru'' Morgan, 1986 *''Euastacus yanga'' Morgan, 1997 *''Euastacus yarraensis'' (McCoy, 1888) *''Euastacus yigara'' Short & Davie, 1993 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「Euastacus」の詳細全文を読む スポンサード リンク
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