维基百科 Gammarus is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most speciose genera of crustaceans.[2] Different species have different optimal conditions, particularly in terms of salinity, and different tolerances; Gammarus pulex, for instance, is a purely freshwater species, while Gammarus locusta is estuarine, only living where the salinity is greater than 25‰.[3] Species of Gammarus are the typical "scuds" of North America and range widely throughout the Holarctic. A considerable number are also found southwards into the Northern Hemisphere tropics, particularly in Southeast Asia.[4] External identifiers for Gammarus Encyclopedia of Life 39782 ITIS 93773 NCBI 45625 WoRMS 101537 Also found in: Wikispecies The following species are included:[5]