Gammarus is an amphipod

Amphipoda

Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. The name amphipoda means "different-footed", and refers to the different forms of appendages, unlike isopods, where all the legs are alike. Of the 7,000 species, 5,500 are classified...

 crustacean

Crustacean

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

 genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 in the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Gammaridae

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....

. It contains more than 200 described species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, making it one of the most speciose genera of crustaceans. Different species have different optimal conditions, particularly in terms of salinity

Salinity

Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...

, and different tolerances; Gammarus pulex

Gammarus pulex

Gammarus pulex is a species of amphipod crustacean found in fresh water across Eurasia. It is a greyish animal, growing to long.-Description:...

, for instance, is a purely freshwater

Freshwater

Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 species, while Gammarus locusta is estuarine, only living where the salinity is greater than 25‰.

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

Holarctic

The Holarctic ecozone refers to the habitats found throughout the northern continents of the world as a whole. This region is divided into the Palearctic, consisting of Northern Africa and all of Eurasia, with the exception of Southeast Asia and the Indian subcontinent, and the Nearctic,...

. A considerable number are also found southwards into the Northern Hemisphere

Northern Hemisphere

The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

 tropics

Tropics

The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately  N and the Tropic of Capricorn in the southern hemisphere at  S; these latitudes correspond to the axial tilt of the Earth...

, particularly in Southeast Asia

Southeast Asia

Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...

.
The following species are included:

• Gammarus abscisus G. Karaman, 1973
• Gammarus abstrusus Hou, Platvoet & Li, 2006
• Gammarus acalceolatus Pinkster, 1970
• Gammarus accolae G. Karaman, 1973
• Gammarus accretus Hou & Li, 2002
• Gammarus acherondytes
  Gammarus acherondytes
  Gammarus acherondytes is a species of crustacean in family Gammaridae. It is endemic to the Illinois Sinkhole Plain of Monroe and St. Clair counties in southwestern Illinois, including Illinois Caverns State Natural Area. Historically it was known from six caves, but in a survey in 1995 the species...
  
  Hubricht & Mackins, 1940
• Gammarus aequicauda (Martynov, 1931)
• Gammarus agrarius G. Karaman, 1973
• Gammarus albimanus G. Karaman, 1968
• Gammarus alsaticus Van Straelen, 1924†
• Gammarus anatoliensis Schellenberg, 1937
• Gammarus angulatus (Martynov, 1930)
• Gammarus angusticoxalis Martynov, 1935
• Gammarus annandalei (Monod, 1924)
• Gammarus annulatus Smith, 1873
• Gammarus anodon Stock, Mirzajani, Vonk, Naderi & Kiabi, 1998
• Gammarus aoculus Hou & Li, 2003
• Gammarus araxenius Derzhavin, 1938
• Gammarus arduus G. Karaman, 1975
• Gammarus argaeus Vávra, 1905
• Gammarus bakhteyaricus Khalayi-Pirbalanty & Sari, 2004
• Gammarus balcanicus Schaferna, 1922
• Gammarus barnaulensis Schellenberg, 1937
• Gammarus belli G. Karaman, 1984
• Gammarus bergi Martynov, 1930
• Gammarus birsteini Karaman & Pinkster, 1977
• Gammarus bosniacus Schäferna, 1922
• Gammarus bousfieldi
  Gammarus bousfieldi
  Gammarus bousfieldi is a species of crustacean in family Gammaridae. It is endemic to the United States....
  
  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 Hou & Li, 2002
• Gammarus chevreuxi
  Gammarus chevreuxi
  Gammarus chevreuxi is a species of crustacean in the family Gammaridae. It was first described by Elsie Wilkins Sexton in 1913. The organism is very similar to Gammarus locusta, but there are certain constant characters which set it apart, for example, the antennae, the fourth side-plates and the...
  
  Sexton, 1913
• Gammarus chimkenti G. Karaman, 1984
• Gammarus chostensis Martynov, 1932
• Gammarus cohabitus Hosinger, Shafer, Fong & Culver, 2008
• 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 Bousfield, 1969
• Gammarus decorosus Meng, Hou & Li, 2003
• Gammarus denticulatus Hou, Li & Morino, 2002
• Gammarus desperatus
  Gammarus desperatus
  Gammarus desperatus is a species of amphipod crustacean in the family Gammaridae.G. desperatus was formerly found at three sites in New Mexico, but it has since been extirpated from two of these sites. G. desperatus only survives within Bitter Lake National Wildlife Refuge...
  
  Cole, 1981
• Gammarus dorsosetosus Mateus & Mateus, 1990
• Gammarus duebeni 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 Iannilli & Ruffo, 2002
• Gammarus emeiensis Hou, Li & Koenemann, 2002
• Gammarus fasciatus Say, 1818
• Gammarus finmarchicus Dahl, 1938
• Gammarus flabellifera Stimpson, 1856
• Gammarus fluviatilis Milne-Edwards, 1840†
• Gammarus fontinalis 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 gracilis Martynov, 1935
• Gammarus gregoryi 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
  Gammarus hyalelloides
  Gammarus hyalelloides is a species of amphipod crustacean in the family Gammaridae. It is endemic to four springs in Jeff Davis County and Reeves County, Texas, and is listed as a vulnerable species on the IUCN Red List.-Description and ecology:...
  
  Cole, 1976
• Gammarus ibericus Margalef, 1951
• Gammarus inaequicauda Stock, 1966
• Gammarus inberbus Karaman & Pinkster, 1977
• Gammarus inopinatus Mateus & Mateus, 1990
• Gammarus insensibilis Stock, 1966
• Gammarus italicus Goedmakers & Pinkster, 1977
• Gammarus izmirensis Özbek, 2007
• Gammarus jacksoni Morino & Whitman, 1995
• Gammarus jaspidus Hou & Li, 2004
• Gammarus jenneri Bynum & Fox, 1977
• Gammarus kamtschaticus Tzvetkova, 1972
• Gammarus kasymovi Aliev, 1997
• Gammarus kesanensis Ozbek & Camus-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
  Gammarus lacustris
  Gammarus lacustris is an aquatic amphipod.-Description:G. lacustris is semi-transparent and lacks a webbed tail. It may be colorless, brown, reddish or bluish in color, depending on the local environment. It has seven abdominal segments, a fused cephalothorax, and two pairs of antennae. Unlike...
  
  G. O. Sars, 1864
• 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 lobifer Stock, Mirzajani, Vonk, Naderi & Kiabi, 1998
• Gammarus locusta (Linnaeus, 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 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 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
  Gammarus pecos
  Gammarus pecos is a species of crustacean in family Gammaridae. It is endemic to the United States.-Source:* Inland Water Crustacean Specialist Group 1996. . Downloaded on 9 August 2007....
  
  Cole & Bousfield, 1970
• Gammarus pellucidus Gurjanova, 1930
• 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
• Gammarus pulex
  Gammarus pulex
  Gammarus pulex is a species of amphipod crustacean found in fresh water across Eurasia. It is a greyish animal, growing to long.-Description:...
  
  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
  Gammarus roeselii
  Gammarus roeseli is a species of freshwater amphipod found across Europe from the Benelux countries to European Turkey. It spread from the Balkans northwards, via the Danube system to establish itself as an alien species in Poland, although it is not an invasive species....
  
  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
  Gammarus setosus
  Gammarus setosus is a gammarid amphipod that inhabits the northern coasts of both the Atlantic and Pacific oceans. Typically, this crustacean is found in the benthic sub-tidal or low inter-tidal regions. Gammarus setosus reproduces once a year in the autumn....
  
  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