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Gammarus lacustris
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Malacostraca
Order:	Amphipoda
Family:	Gammaridae
Genus:	Gammarus
Species:	G. lacustris
Binomial name
	Gammarus lacustris; G. O. Sars, 1863

Gammarus lacustris is an aquatic amphipod.

Description

Gammarus 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 other crustaceans, amphipods lack carapaces and have laterally compressed bodies. Gammarids are referred to as scuds or sideswimmers. G. lacustris resembles a freshwater shrimp.

Life cycle

The female carries eggs in a brood pouch on its ventral side. G. lacustris in higher elevations were more likely to have fewer but larger eggs than those living at lower elevations.^[1] G. lacustris undergoes several molts and juveniles resemble the adult.

Ecology

Gammarus lacustris plays an important role in many of the freshwater ecosystems that it inhabits. It is a detritivore and may also consume algae, mainly diatoms.^[1] It is considered an indicator species for the overall health and stability of the ecosystem. G. lacustris can also inhabit a wide array of environments, ranging from low altitude calcium-rich lakes to high altitude, cold, and calcium-poor lakes. This influences its biology: at low altitudes, it is known to die after first reproduction, but in colder waters, it lives to reproduce repeatedly.^[2]

Temperature

In many species feeding behaviour is affected by temperature, i.e. the amount of food consumed often increases at warmer temperatures.^[3] However, when G. lacustris feeds on three different parasite species (Diplostomum spp., Apatemon spp. and Trichobilharzia spp.) no such effect of temperature on feeding is seen.^[4]

Parasites

As a small aquatic invertebrate G. lacustris is an important food source for many organisms. Birds, fishes, and some insects are known to prey upon G. lacustris. As many other species of small invertebrates, it serves as an intermediate host for several parasite species (e.g. Pomphorhynchus laevis).^[5]^[6] G. lacustris typically shows photophobic behaviour, but when parasitized this can be altered to photophilic behaviour when infected by Pomphorhynchus laevis,^[6] which is a host manipulation parasite, like many others.^[5]^[7] Parasites can affect the diel migration of G. lacustris, making it more visible and susceptible to predation most likely aiding parasite transmission.^[5]^[7]^[8]^[9] More mature parasites have greater effects on hosts.^[10]

Distribution

Gammarus lacustris has been noted in northwestern Europe, Russia, and North America.^[1]^[11] Its precise range has yet to be defined. It can be found in shallow or deep lakes and in slow-moving rivers. It is more abundant in fishless lakes than in those with fish. Its distribution follows the thermocline in the water.^[11]

References

^ ^a ^b ^c F. M. Wilhelm; D. W. Schindler (2001). "Reproductive strategies of Gammarus lacustris (Crustacea: Amphipoda) along an elevation gradient". Functional Ecology. 14 (4): 413–422. doi:10.1046/j.1365-2435.2000.00426.x. JSTOR 2656534.
^ Østbye, Kjartan; Østbye, Eivind; Lien, Anne May; Lee, Laura R.; Lauritzen, Stein-Erik; Carlini, David B. (25 October 2018). "Morphology and life history divergence in cave and surface populations of Gammarus lacustris (L.)". PLOS ONE. 13 (10): e0205556. doi:10.1371/journal.pone.0205556. PMC 6201897. PMID 30359400.
^ Englund, Göran; Öhlund, Gunnar; Hein, Catherine L.; Diehl, Sebastian (2011). "Temperature dependence of the functional response: Temperature dependence of consumption". Ecology Letters. 14 (9): 914–921. doi:10.1111/j.1461-0248.2011.01661.x. PMID 21752171.
^ Born-Torrijos, Ana; Paterson, Rachel A.; van Beest, Gabrielle S.; Schwelm, Jessica; Vyhlídalová, Tereza; Henriksen, Eirik H.; Knudsen, Rune; Kristoffersen, Roar; Amundsen, Per-Arne; Soldánová, Miroslava (2020). "Temperature does not influence functional response of amphipods consuming different trematode prey". Parasitology Research. 119 (12): 4271–4276. doi:10.1007/s00436-020-06859-1. PMC 7447966. PMID 32845358.
^ ^a ^b ^c Janice Moore (1984). "Altered behavioral responses in intermediate hosts – an acanthoceptalan parasite strategy". The American Naturalist. 123 (4): 572–577. doi:10.1086/284224. JSTOR 2461000. S2CID 86700440.
^ ^a ^b Marie-Jeanne Perrot-Minnot (2003). "Larval morphology, genetic divergence, and contrasting levels of host manipulation between forms of Pomphorhynchus laevis". International Journal for Parasitology. 34 (1): 45–54. doi:10.1016/j.ijpara.2003.10.005. PMID 14711589.
^ ^a ^b K. D. Lafferty (1999). "The evolution of trophic transmission". Parasitology Today. 15 (3): 111–115. CiteSeerX 10.1.1.58.1452. doi:10.1016/S0169-4758(99)01397-6. PMID 10322324.
^ Robert Poulin (1995). ""Adaptive" changes in the behaviour of parasitized animals: a critical review". International Journal for Parasitology. 25 (12): 1371–1383. doi:10.1016/0020-7519(95)00100-X. PMID 8719948.
^ F. Thomas; Robert Poulin (1998). "Nonmanipulative parasites in manipulated hosts: 'hitchhikers' or simply 'lucky passengers'?". The Journal of Parasitology. 84 (5): 1059–1061. doi:10.2307/3284648. JSTOR 3284648. PMID 9794658.
^ N. Franceshi; A. Bauer; L. Bollache; T. Rigaud (2008). "The effects of parasite age and intensity on variability in acanthocephalan-induced behavioural manipulation". International Journal for Parasitology. 38 (10): 1161–1170. doi:10.1016/j.ijpara.2008.01.003. PMID 18314127.
^ ^a ^b Egor S. Zadereev; Alexander P. Tolomeyev; Anton V. Drobotov; Anna Yu. Emeliyanova; Mikhail V. Gubanov (2010). "The vertical distribution and abundance of Gammarus lacustris in the pelagic zone of the meromictic lakes Shira and Shunet (Khakassia, Russia)". Aquatic Ecology. 44 (3): 531–539. doi:10.1007/s10452-010-9329-5. S2CID 24786971.