''Gammarus'' is an

amphipod Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Gammaridae Gammaridae is a family of amphipods. In North America they are included among the folk taxonomic category of " scuds", and otherwise gammarids is usually used as a common name. They have a wide distribution, centered on Eurasia, and are eury ...

. It contains more than 200 described

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

, making it one of the most species-rich genera of crustaceans. Different species have different

optimal Mathematical optimization (alternatively spelled ''optimisation'') or mathematical programming is the selection of a best element, with regard to some criterion, from some set of available alternatives. It is generally divided into two subfi ...

conditions, particularly in terms of

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

, and different tolerances; ''

Gammarus pulex ''Gammarus pulex'' is a species of amphipod crustacean found in fresh water across much of Europe. It is a greyish animal, growing to long. Description Adult males of ''Gammarus pulex'' may reach a total length of , while females only grow to . ...

'', for instance, is a purely

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

species, while ''

Gammarus locusta ''Gammarus locusta'' is a species in the family Gammaridae ("scuds"), in the order Amphipoda ("amphipods").bugguide.net

'' is estuarine, only living where the salinity is greater than 25

‰ Per mille (from Latin , "in each thousand") is an expression that means parts per thousand. Other recognised spellings include per mil, per mill, permil, permill, or permille. The associated sign is written , which looks like a percent si ...

. Species of ''Gammarus'' are the typical " scuds" of North America and range widely throughout the

Holarctic The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical reg ...

. A considerable number are also found southwards into the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

, particularly in

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical United Nations geoscheme for Asia#South-eastern Asia, south-eastern region of Asia, consistin ...

Species

The following species are included: Four new species were found in 2018 on the

Tibetan Plateau The Tibetan Plateau (, also known as the Qinghai–Tibet Plateau or the Qing–Zang Plateau () or as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia covering most of the Ti ...

. Four more new species were described from the

Chihuahuan Desert The Chihuahuan Desert ( es, Desierto de Chihuahua, ) is a desert ecoregion designation covering parts of northern Mexico and the southwestern United States. It occupies much of far West Texas, the middle to lower Rio Grande Valley and the lo ...

in 2021. *''

Gammarus abscisus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly ...

'' G. Karaman, 1973 *''

Gammarus abstrusus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly ...

'' Hou, Platvoet & Li, 2006 *'' Gammarus acalceolatus'' Pinkster, 1970 *'' Gammarus accolae'' G. Karaman, 1973 *'' Gammarus accretus'' Hou & Li, 2002 *'' Gammarus acherondytes'' Hubricht & Mackins, 1940 *''

Gammarus aequicauda ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' (Martynov, 1931) *'' Gammarus agrarius'' G. Karaman, 1973 *'' Gammarus albimanus'' G. Karaman, 1968 *'' Gammarus alsaticus'' Van Straelen, 1924† *'' Gammarus altus'' Hou & Li, 2018 *''

Gammarus anatoliensis ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Schellenberg, 1937 *'' Gammarus angulatus'' (Martynov, 1930) *''

Gammarus angusticoxalis ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Martynov, 1935 *'' Gammarus annandalei'' (Monod, 1924) *'' Gammarus annulatus'' Smith, 1873 *'' Gammarus anodon'' Stock, Mirzajani, Vonk, Naderi & Kiabi, 1998 *''

Gammarus aoculus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Hou & Li, 2003 *'' Gammarus araxenius'' Derzhavin, 1938 *'' Gammarus arduus'' G. Karaman, 1975 *''

Gammarus argaeus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Vávra, 1905 *'' Gammarus bakhteyaricus'' Khalayi-Pirbalanty & Sari, 2004 *''

Gammarus balcanicus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Schaferna, 1922 *'' Gammarus barnaulensis'' Schellenberg, 1937 *''

Gammarus baysali ''Gammarus baysali'' is a cave-dwelling species of freshwater amphipod crustacean, found in Turkey. The species belongs to the broader ''Gammarus pulex'' group and was scientifically described in 2013 from Cumayanı Cave, Zonguldak Province Zo ...

'' Özbek et al., 2013 *'' Gammarus belli'' G. Karaman, 1984 *'' Gammarus bergi'' Martynov, 1930 *'' Gammarus birsteini'' Karaman & Pinkster, 1977 *''

Gammarus bosniacus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Schäferna, 1922 *'' Gammarus bousfieldi'' Cole & Minckley, 1961 *'' Gammarus brevicornis'' (Martynov, 1935) *'' Gammarus brevipodus'' Hou, Li & Platvoet, 2004 *'' Gammarus breviramus'' Bousfield & Elwood, 1971 *'' Gammarus bucharensis'' Martynov, 1935 *'' Gammarus caparti'' Petre-Stroobants, 1981 *'' Gammarus caucasicus'' Martynov, 1932 *'' Gammarus caudisetus'' Viviani, 1805 *''

Gammarus chaohuensis ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Hou & Li, 2002 *'' Gammarus chevreuxi'' Sexton, 1913 *'' Gammarus chimkenti'' G. Karaman, 1984 *''

Gammarus chostensis ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Martynov, 1932 *''

Gammarus cohabitus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Hosinger, Shafer, Fong & Culver, 2008 *'' Gammarus colei'' sp. nov. *'' Gammarus comosus'' Hou, Li & Gao, 2005 *'' Gammarus craspedotrichus'' Hou & Li, 2002 *'' Gammarus crenulatus'' G. S. Karaman & Pinkster, 1977 *'' Gammarus crinicaudatus'' Stock, Mirzajani, Vonk, Naderi & Kiabi, 1998 *'' Gammarus crinicornis'' Stock, 1966 *'' Gammarus crispus'' Martynov, 1932 *'' Gammarus curvativus'' Hou & Li, 2003 *'' Gammarus dabanus'' Tachteew & Mekhanikova, 2000 *''

Gammarus daiberi ''Gammarus'' is an Amphipoda, amphipod crustacean genus in the family (biology), family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimu ...

'' Bousfield, 1969 *'' Gammarus decorosus'' Meng, Hou & Li, 2003 *''

Gammarus denticulatus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Hou, Li & Morino, 2002 *''

Gammarus desperatus ''Gammarus desperatus'', commonly known as Noel's Amphipod, is a species of small, amphipod crustacean in the family Gammaridae. Noel's Amphipod was formerly found at three sites in New Mexico, but it has since been extirpated from two of these ...

'' Cole, 1981 *'' Gammarus dorsosetosus'' Mateus & Mateus, 1990 *''

Gammarus duebeni ''Gammarus'' is an Amphipoda, amphipod crustacean genus in the family (biology), family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimu ...

'' Liljeborg, 1852 *'' Gammarus dulensis'' S. Karaman, 1929 *'' Gammarus edwardsi'' Bate, 1862 *'' Gammarus effultus'' G. Karaman, 1975 *'' Gammarus electrus'' Hou & Li, 2003 *'' Gammarus elevatus'' Hou, Li & Morino, 2002 *''

Gammarus elvirae ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Iannilli & Ruffo, 2002 *'' Gammarus emeiensis'' Hou, Li & Koenemann, 2002 *''

Gammarus fasciatus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Say, 1818 *'' Gammarus finmarchicus'' Dahl, 1938 *'' Gammarus flabellifera'' Stimpson, 1856 *'' Gammarus fluviatilis'' Milne-Edwards, 1840† *''

Gammarus fontinalis ''Gammarus'' is an Amphipoda, amphipod crustacean genus in the family (biology), family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimu ...

'' Costa, 1883 *'' Gammarus fossarum'' Koch, 1836 *'' Gammarus frater'' Karaman & Pinkster, 1977 *'' Gammarus frigidus'' Hou & Li, 2004 *'' Gammarus galgosensis'' Lee & Kim, 2004 *'' Gammarus galgosensis'' Lee & Kim, 1980 *'' Gammarus gauthieri'' (S. Karaman, 1935) *'' Gammarus glabratus'' Hou & Li, 2003 *'' Gammarus goedmakersae'' G. S. Karaman & Pinkster, 1977 *''

Gammarus gonggaensis ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Hou & Li, 2018 *'' Gammarus gracilis'' Martynov, 1935 *''

Gammarus gregoryi ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Tattersall, 1924 *'' Gammarus halilicae'' G. Karaman, 1969 *'' Gammarus hegmatanensis'' Hekmatara, Sari & Baladehi, 2011 *'' Gammarus hirsutus'' Martynov, 1935 *'' Gammarus hongyuanensis'' Barnard & Dai, 1988 *'' Gammarus hoonsooi'' Lee, 1986 *'' Gammarus hyalelloides'' Cole, 1976 *'' Gammarus ibericus'' Margalef, 1951 *'' Gammarus inaequicauda'' Stock, 1966 *'' Gammarus inberbus'' Karaman & Pinkster, 1977 *'' Gammarus inopinatus'' Mateus & Mateus, 1990 *''

Gammarus insensibilis ''Gammarus insensibilis'', the lagoon sand shrimp, is a species of amphipod crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remi ...

'' Stock, 1966 *'' Gammarus italicus'' Goedmakers & Pinkster, 1977 *'' Gammarus izmirensis'' Özbek, 2007 *'' Gammarus jacksoni'' Morino & Whitman, 1995 *''

Gammarus jaspidus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Hou & Li, 2004 *'' Gammarus jenneri'' Bynum & Fox, 1977 *''

Gammarus kamtschaticus ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Tzvetkova, 1972 *''

Gammarus kangdingensis ''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...

'' Hou & Li, 2018 *''Gammarus kasymovi'' Aliev, 1997 *''Gammarus katagani'' Özbek, 2012 *''Gammarus kesanensis'' Özbek & Camur-Elipek, 2010 *''Gammarus kesslerianus'' Martynov, 1931 *''Gammarus kischineffensis'' Schellenberg, 1937 *''Gammarus komareki'' (Schaferna, 1922) *''Gammarus korbuensis'' Martynov, 1930 *''Gammarus koshovi'' Bazikalova, 1946 *''Gammarus kyonggiensis'' Lee & Seo, 1990 *''Gammarus laborifer'' Karaman & Pinkster, 1977 *''Gammarus lacustris'' G. O. Sars, 1864 *''Gammarus langi'' sp. nov. *''Gammarus lasaensis'' Barnard & Dai, 1988 *''Gammarus laticoxalis'' Karaman & Pinkster, 1977 *''Gammarus lawrencianus'' Bousfield, 1956 *''Gammarus lecroyae'' Thoma & Heard, 2009 *''Gammarus ledoyeri'' G. Karaman, 1987 *''Gammarus lepoliensis'' Jazdzewski & Konopacka, 1989 *''Gammarus lichuanensis'' Hou & Li, 2002 *''Gammarus limnaeus'' S. I. smith, 1874 *''Gammarus limosus'' Hou & Li, 2018 *''Gammarus lobifer'' Stock, Mirzajani, Vonk, Naderi & Kiabi, 1998 *''

Gammarus locusta ''Gammarus locusta'' is a species in the family Gammaridae ("scuds"), in the order Amphipoda ("amphipods").bugguide.net

'' (Carl Linnaeus, Linnaeus, 10th edition of Systema Naturae, 1758) *''Gammarus longipedis'' Karaman & Pinkster, 1987 *''Gammarus longisaeta'' Lee & Seo, 1992 *''Gammarus lophacanthus'' Hou & Li, 2002 *''Gammarus lordeganensis'' Khalayi-Pirbalanty & Sari, 2004 *''Gammarus lychnidensis'' Schellenberg, 1943 *''Gammarus macedonicus'' G. Karaman, 1976 *''Gammarus madidus'' Hou & Li, 2005 *''Gammarus malpaisensis'' sp. nov. *''Gammarus marmouchensis'' Fadil, 2006 *''Gammarus maroccanus'' Fadil & Dakki, 2001 *''Gammarus martensi'' Hou & Li, 2004 *''Gammarus matienus'' Derzhavin, 1938 *''Gammarus miae'' Mateus & Mateus, 1990 *''Gammarus microps'' Pinkster & Goedmakers, 1975 *''Gammarus minus'' Say, 1818 *''Gammarus mladeni'' Karaman & Pinkster, 1977 *''Gammarus monospeliensis'' Pinkster, 1972 *''Gammarus montanus'' Hou, Li & Platvoet, 2004 *''Gammarus mucronatus'' Say, 1818 *''Gammarus murarius'' Hou & Li, 2004 *''Gammarus nekkensis'' Uchida, 1935 *''Gammarus ninglangensis'' Hou & Li, 2003 *''Gammarus nipponensis'' Uéno, 1940 *''Gammarus nox'' Stock, 1995 *''Gammarus nudus'' Martynov, 1931 *''Gammarus obnixus'' Karaman & Pinkster, 1977 *''Gammarus obruki'' Özbek, 2012 *''Gammarus oceanicus'' Segerstråle, 1947 *''Gammarus ocellatus'' Martynov, 1930 *''Gammarus ochridensis'' (Schäferna, 1926) *''Gammarus odaensis'' Lee & Kim, 1980 *''Gammarus odettae'' Mateus & Mateus, 1990 *''Gammarus oeningensis'' Heer, 1865† *''Gammarus orinos'' Pinkster & Schol, 1984 *''Gammarus oronticus'' Alouf, 1979 *''Gammarus osellai'' Karaman & Pinkster, 1977 *''Gammarus pageti'' Mateus & Mateus, 1990 *''Gammarus palustris'' Bousfield, 1969 *''Gammarus parechiniformis'' G. Karaman, 1977 *''Gammarus paricrenatus'' Stock, Mirzajani, Vonk, Naderi & Kiabi, 1998 *''Gammarus parthicus'' Stock, Mirzajani, Vonk, Naderi & Kiabi, 1998 *''Gammarus paucispinus'' Hou & Li, 2002 *''Gammarus pavlovici'' *''Gammarus pavo'' Karaman & Pinkster, 1977 *''Gammarus paynei'' Delong, 1992 *''Gammarus pecos'' Cole & Bousfield, 1970 *''Gammarus pellucidus'' Eupraxie Gurjanova, Gurjanova, 1930 *''Gammarus percalacustris'' sp. nov. *''Gammarus pexus'' Hou & Li, 2005 *''Gammarus platvoeti'' Hou & Li, 2003 *''Gammarus pljakici'' G. Karaman, 1964 *''Gammarus plumipes'' Mateus & Mateus, 1990 *''Gammarus praecyrius'' Derzhavin, 1941† *''Gammarus preciosus'' Wang, Hou & Li, 2009 *''Gammarus pretzmanni'' Mateus & Mateus, 1990 *''Gammarus proiectus'' Stock, Mirzajani, Vonk, Naderi & Kiabi, 1998 *''Gammarus pseudoanatoliensis'' Karaman & Pinkster, 1987 *''Gammarus pseudolimnaeus'' Bousfield, 1958 *''Gammarus pseudosyriacus'' Karaman & Pinkster, 1977 *''

'' Linnaeus, 1758 *''Gammarus qiani'' Hou & Li, 2002 *''Gammarus rambouseki'' S. Karaman, 1931 *''Gammarus retzi'' Maikovsky, 1941† *''Gammarus rifatlensis'' Fadil, 2006 *''Gammarus riparius'' Hou & Li, 2002 *''Gammarus roeselii'' Gervais, 1835 *''Gammarus rouxi'' Pinkster & Goedmakers, 1975 *''Gammarus salemaai'' G. Karaman, 1985 *''Gammarus salinus'' Spooner, 1947 *''Gammarus sepidannus'' Zamanpoore, Poeckl, Grabowski & Schiemer, 2009 *''Gammarus setosus'' Dementieva, 1931 *''Gammarus shanxiensis'' Barnard & Dai, 1988 *''Gammarus shenmuensis'' Hou & Li, 2004 *''Gammarus sichuanensis'' Hou, Li & Zheng, 2002 *''Gammarus sinuolatus'' Hou & Li, 2004 *''Gammarus sirvannus'' Hekmatara, Sari & Baladehi, 2011 *''Gammarus sketi'' G. Karaman, 1989 *''Gammarus sobaegensis'' G. Karaman, 1984 *''Gammarus solidus'' G. Karaman, 1977 *''Gammarus songirdaki'' G. Karaman, 1984 *''Gammarus soyoensis'' Lee & Kim, 1980 *''Gammarus spelaeus'' Martynov, 1931 *''Gammarus spinipalmus'' (Chen, 1939) *''Gammarus spooneri'' G. Karaman, 1991 *''Gammarus stagnarius'' Hou, Li & Morino, 2002 *''Gammarus stalagmiticus'' Hou & Li, 2005 *''Gammarus stankokaramani'' G. Karaman, 1976 *''Gammarus stojicevici'' (S. Karaman, 1929) *''Gammarus stupendus'' Pinkster, 1983 *''Gammarus subtypicus'' Stock, 1966 *''Gammarus suifunensis'' Martynov, 1925 *''Gammarus syriacus'' Chevreux, 1895 *''Gammarus takesensis'' Hou, Li & Platvoet, 2004 *''Gammarus taliensis'' Shen, 1954 *''Gammarus tauricus'' Martynov, 1931 *''Gammarus teletzkensis'' Martynov, 1930 *''Gammarus tigrinus'' Sexton, 1939 *''Gammarus topkarai'' Özbek & Balik, 2009 *''Gammarus translucidus'' Hou, Li & Li, 2004 *''Gammarus troglophilus'' Hubricht & Mackins, 1940 *''Gammarus truncatus'' Martynov, 1930 *''Gammarus turanus'' Martynov, 1935 *''Gammarus uludagi'' G. S. Karaman, 1975 *''Gammarus unguiserratus'' Costa, 1853 *''Gammarus ustaoglui'' Özbek & Guloglu, 2005 *''Gammarus varsoviensis'' Jazdzewski, 1975 *''Gammarus vignai'' Pinkster & Karaman, 1978 *''Gammarus wangbangensis'' Lee & Seo, 1990 *''Gammarus wautieri'' Roux, 1967 *''Gammarus wilkitzkii'' Birula, 1897 *''Gammarus xiangfengensis'' Hou & Li, 2002 *''Gammarus zaddachi'' Sexton, 1912 *''Gammarus zagrosensis'' Zamanpoore, Poeckl, Grabowski & Schiemer, 2009 *''Gammarus zeongogensis'' Lee & Kim, 1980

References

{{Taxonbar, from=Q548451 Gammarus, Gammaridea Taxonomy articles created by Polbot Crustacean genera