Gammarus

Fabricius, 1775

scuds, freshwater shrimp, sideswimmers

Species Guides

Gammarus fasciatus
Gammarus lacustris(lacustrine scud)
Gammarus locusta(scud)
Gammarus mucronatus(scud)
Gammarus pseudolimnaeus(Northern Spring Amphipod)
Gammarus seideli(Seidel's Scud)

Gammarus is a of amphipod crustaceans in the Gammaridae, containing over 200 described and representing one of the most species-rich crustacean genera. Species occupy diverse aquatic ranging from purely freshwater to estuarine and marine environments, with salinity varying markedly among species. The genus is widely distributed throughout the Holarctic region, with additional species extending into tropical Southeast Asia. Gammarus species serve important ecological functions as and in aquatic .

Gammarus lacustris by (c) Erin McKittrick, some rights reserved (CC BY), uploaded by Erin McKittrick. Used under a CC-BY license.

Gammarus seideli by (c) Dr. Andrew G. Cannizzaro, some rights reserved (CC BY), uploaded by Dr. Andrew G. Cannizzaro. Used under a CC-BY license.

Gammarus fasciatus by no rights reserved, uploaded by nmacelko2. Used under a CC0 license.

Pronunciation

How to pronounce Gammarus: /ˈɡæməˌrəs/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Images

Habitat

occupy diverse aquatic environments including freshwater streams, rivers, and lakes; estuarine with salinities above 25‰; and marine coastal waters. Specific habitat requirements vary by species: G. pulex is restricted to freshwater, G. locusta requires estuarine conditions with salinity >25‰, and G. troglomorphus has been documented from subterranean desert sinkhole waters. Many species prefer well-buffered, calcium- and magnesium-rich lotic environments.

Distribution

Widely distributed throughout the Holarctic region, including North America, Europe, and Asia. Range extends southward into the Northern Hemisphere tropics, particularly in Southeast Asia. Documented from the Arctic Ocean south to Newfoundland (G. wilkitzkii), the Gulf of Mexico (G. mucronatus), the Tibetan Plateau, the Chihuahuan Desert, and the Koytendag mountains of Turkmenistan.

Life Cycle

Reproductive strategies vary among . G. wilkitzkii produces a single large of large in autumn or early winter, with hatching and release from April to July; individuals mature at relatively large size. G. stoerensis and G. mucronatus produce multiple smaller broods of small eggs: G. stoerensis breeds between spring and autumn with a resting stage in late winter, while G. mucronatus produces several summer broods.

Ecological Role

Native Gammarus have been demonstrated to provide biotic resistance against amphipods through . G. pulex and G. duebeni effectively prey upon the invasive Crangonyx pseudogracilis, with G. pulex being the more effective ; this predatory can prevent establishment of invaders where native are abundant. Species serve as intermediate for helminth including trematodes (Podocotyle atomon, P. reflexa), cestodes (Microsomacantus sp.), (Spiruridae), and acanthocephalans (Polymorphus phippsi, Echinorhynchus gadi).