Editing Amphipoda (section)

==Ecology==
[[File:Talitrus saltator 2c.jpg|thumb|right|''[[Talitrus saltator]]'' is an abundant animal of sandy beaches around [[Europe]].]]
[[File:Expl1152 - Flickr - NOAA Photo Library.jpg|thumb|right|Dorsal (top) view of a newly discovered amphipod living in a [[commensal]] relationship with a [[bamboo coral]]]]

Amphipods are found in almost all aquatic environments, from [[fresh water]] to water with twice the [[salinity]] of [[Seawater|sea water]]<ref name="Wade"/> and even in the [[Challenger Deep]], the deepest known point in the ocean.<ref name="James Cameron on Earth's Deepest Spot: Desolate, Lunar-Like">{{cite web |author=National Geographic |title=James Cameron on Earth's Deepest Spot: Desolate, Lunar-Like |url=http://news.nationalgeographic.com/news/2012/03/120326-james-cameron-mariana-trench-challenger-deepest-lunar-sub-science/ |archive-url=https://web.archive.org/web/20120328064958/http://news.nationalgeographic.com/news/2012/03/120326-james-cameron-mariana-trench-challenger-deepest-lunar-sub-science/ |url-status=dead |archive-date=March 28, 2012 |date=27 March 2012 |publisher=National Geographic Society |access-date=27 March 2012 }}</ref> They are almost always an important component of aquatic ecosystems,<ref name="Lowry">{{cite web |url=http://www.crustacea.net/crustace/amphipoda/index.htm |title=Introduction |work=Amphipoda: Families |first1=J.&nbsp;K. |last1=Lowry |first2=R.&nbsp;T. |last2=Springthorpe |publisher=[[Australian Museum]] |access-date=April 5, 2010 |archive-url=https://web.archive.org/web/20060221225649/http://crustacea.net/crustace/amphipoda/index.htm |archive-date=February 21, 2006  }}</ref> often acting as mesograzers.<ref name="Duffy">{{Cite journal |last1=Duffy |first1=J.&nbsp;E. |first2=Mark E. |last2=Hay |year=2000 |title=Strong impacts of grazing amphipods on the organization of a benthic community |journal=Ecological Monographs |volume=70 |issue=2 |pages=237–263 |doi=10.1890/0012-9615(2000)070[0237:SIOGAO]2.0.CO;2|citeseerx=10.1.1.473.4746 |s2cid=54598097 }}</ref> Most species in the suborder Gammaridea are [[epibenthos|epibenthic]], although they are often collected in [[plankton]] samples. Members of the Hyperiidea are all planktonic and marine.<ref name="TAFI"/> Many are [[symbiosis|symbionts]] of gelatinous animals, including [[salp]]s, [[Medusa (biology)|medusae]], [[Siphonophorae|siphonophores]], colonial [[radiolaria]]ns and [[Ctenophora|ctenophores]], and most hyperiids are associated with gelatinous animals during some part of their life cycle.<ref>{{cite journal |journal=[[Deep-Sea Research]] |year=1977 |volume=24 |pages=465–488 |title=The associations of Amphipoda Hyperiidea with gelatinous zooplankton. II. Associations with Cnidaria, Cteuophora and Radiolaria |first1=G.&nbsp;R. |last1=Harbison |first2=D.&nbsp;C. |last2=Biggs |first3=L.&nbsp;P. |last3=Madin |doi=10.1016/0146-6291(77)90484-2 |issue=5|bibcode=1977DSR....24..465H }}</ref> Some 1,900 species, or 20% of the total amphipod diversity, live in fresh water or other non-marine waters. Notably rich endemic amphipod faunas are found in the ancient [[Lake Baikal]] and waters of the [[Caspian Sea]] basin.<ref name=Fresh>{{cite journal |first1=R. |last1=Väinölä |first2=J.&nbsp;D.&nbsp;S. |last2=Witt |first3=M. |last3=Grabowski |first4=J.&nbsp;H. |last4=Bradbury |first5=K. |last5=Jazdzewski |first6=B. |last6=Sket |year=2008 |title=Global diversity of amphipods (Amphipoda, Crustacea) in freshwater |url=http://decapoda.nhm.org/pdfs/27701/27701.pdf |journal=[[Hydrobiologia]] |volume=595 |issue=1 |pages=241–255 |doi=10.1007/s10750-007-9020-6|s2cid=4662681 }}</ref>

The [[landhopper]]s of the family [[Talitridae]] (which also includes semi-terrestrial and marine animals) are [[terrestrial animal|terrestrial]], living in damp environments such as [[leaf litter]].<ref name="Massey">{{cite web |url=http://soilbugs.massey.ac.nz/amphipoda.php |title=Amphipoda |work=Guide to New Zealand Soil Invertebrates |publisher=[[Massey University]] |access-date=April 7, 2010 |first1=M.&nbsp;A. |last1=Minor |first2=A.&nbsp;W. |last2=Robertson |date=March 5, 2010 |archive-url=https://web.archive.org/web/20100510121618/http://soilbugs.massey.ac.nz/amphipoda.php |archive-date=10 May 2010  |url-status=live}}</ref> Landhoppers have a wide distribution in areas that were formerly part of [[Gondwana]], but have colonised parts of [[Europe]] and [[North America]] in recent times.

Around 750 species in 160 genera and 30 families are [[troglobite|troglobitic]], and are found in almost all suitable habitats, but with their [[center of diversity|centres of diversity]] in the [[Mediterranean Basin]], southeastern [[North America]] and the [[Caribbean]].<ref>{{cite book |chapter=Crustacea |first=Horton H. III |last=Hobbs |editor-first = John | editor-last = Gunn |title=Encyclopedia of Caves and Karst Science |publisher=[[Routledge]] |year=2003 |url=http://www.routledge-ny.com/ref/caves/crustacea.pdf |isbn=978-1-57958-399-6 |pages=254–257}}</ref>

In populations found in Benthic ecosystems, amphipods play an essential role in controlling brown algae growth.<ref name="Duffy" /> The mesograzer behaviour of amphipods greatly contributes to the suppression of brown algal dominance in the absence of amphipod predators.<ref name="Duffy" /> Amphipods display a strong preference for brown algae in Benthic ecosystems, but due to removal of mesograzers by predators such as fish, brown algae is able to dominate these communities over green and red algae species.<ref name="Duffy"/>

===Morphology===
Compared to other crustacean groups, such as the [[Isopoda]], [[Rhizocephala]] or [[Copepod]]a, relatively few amphipods are [[parasitism|parasitic]] on other animals. The most notable example of parasitic amphipods are the [[whale louse|whale lice]] (family Cyamidae). Unlike other amphipods, these are dorso-ventrally flattened, and have large, strong claws, with which they attach themselves to [[baleen whale]]s. They are the only parasitic crustaceans which cannot swim during any part of their [[Biological life cycle|life cycle]].<ref>{{cite web|url=http://web.viu.ca/goatert/PARASITE/PARAMPH.HTM |title=Parasitic Amphipoda |publisher=[[Vancouver Island University]] |access-date=April 7, 2010 |date=May 4, 1996 |first=Tim |last=Goater |work=Interactive Parasitology  |archive-url=https://web.archive.org/web/20100714173551/http://web.viu.ca/goatert/PARASITE/PARAMPH.HTM |archive-date=July 14, 2010 }}</ref>

===Foraging behaviour===
Most amphipods are [[detritivore]]s or [[scavenger]]s,<ref name="Wade" /> with some being [[Grazing|grazers]] of [[algae]], [[omnivore]]s or [[predator]]s<ref name="TAFI" /> of small [[insect]]s and [[crustacean]]s.<ref name="Wade" /> Food is grasped with the front two pairs of legs, which are armed with large claws.<ref name="Wade" /> More immobile species of amphipods eat higher quantities of less nutritious food rather than actively seeking more nutritious food.<ref name="Cruz_Rivera_2000"/> This is a type of compensatory feeding.<ref name="Cruz_Rivera_2000" /> This behaviour may have evolved to minimise predation risk when searching for other foods.<ref name="Cruz_Rivera_2000" /> ''Ampithoe longimana'', for example, is more sedentary than other species and have been observed to remain on host plants longer.<ref name="Cruz_Rivera_2000" /> In fact, when presented with both high- and low-nutrition food options, the sedentary species ''Ampithoe longimana'' does not distinguish between the two options.<ref name="Cruz_Rivera_2000"/> Other amphipod species, such as ''[[Gammarus mucronatus]]'' and ''Elasmopus levis'', which have superior [[Anti-predator adaptation|predator avoidance]] and are more mobile, are better able to pursue different food sources.<ref name="Cruz_Rivera_2000">{{Cite journal |last1=Cruz-Rivera |first1=Edwin |first2=Mark E. |last2=Hay |year=2000 |title=Can quantity replace quality? Food choice, compensatory feeding, and fitness of marine mesograzers |journal=[[Ecology (journal)|Ecology]] |volume=81 |pages=201–219 |doi=10.1890/0012-9658(2000)081[0201:CQRQFC]2.0.CO;2|hdl=1853/36755 |hdl-access=free }}</ref> In species without the compensatory feeding ability, survivorship, fertility, and growth can be strongly negatively affected in the absence of high-quality food.<ref name="Cruz_Rivera_2000"/> Compensatory feeding may also explain the year-round presence of ''A.&nbsp;longimana'' in certain waters.<ref name="Cruz_Rivera_2001">{{Cite journal |last1=Cruz-Rivera |first1=Edwin |first2=Mark E. |last2=Hay |year=2001 |title=Macroalgal traits and the feeding and fitness of an herbivorous amphipod: the roles of selectivity, mixing, and compensation |journal=[[Marine Ecology Progress Series]] |volume=218 |pages=249–266 |url=https://www.int-res.com/abstracts/meps/v218/p249-266/ |doi=10.3354/meps218249|bibcode=2001MEPS..218..249C |doi-access=free |hdl=1853/34241 |hdl-access=free }}</ref> Because algal presence changes throughout the year in certain communities, the evolution of flexible feeding techniques such as compensatory feeding may have been [[Fitness (biology)|beneficial to survival]].<ref name="Cruz_Rivera_2001"/>

''Ampithoe longimana'' has been observed to avoid certain compounds when foraging for food.<ref name="Schnitzler"/> In response to this avoidance, species of seaweed such as ''Dictyopteris membranacea'' or ''Dictyopteris hoytii'' have evolved to produce C<sub>11</sub> sulfur compounds and C-9 oxo-acids in their bodies as defense mechanisms that specifically deter amphipods instead of deterrence to consumption by other predators.<ref name="Schnitzler">{{Cite journal |last1=Schnitzler |first1=Iris |first2=Georg |last2=Pohnert |first3=Mark |last3=Hay |first4=Wilhelm |last4=Boland |year=2001 |title=Chemical defense of brown algae (''Dictyopteris'' spp.) against the herbivorous amphipod ''Ampithoe longimana'' |journal=[[Oecologia]] |volume=126 |issue=4 |pages=515–521 |doi=10.1007/s004420000546|pmid=28547236 |bibcode=2001Oecol.126..515S |s2cid=12281845 }}</ref>

The incidence of cannibalism and [[intraguild predation]] is relatively high in some species,<ref name="Dick">{{cite journal |first=Jaimie T.&nbsp;A. |last=Dick |year=1995 |title=The cannibalistic behaviour of two ''Gammarus'' species (Crustacea: Amphipoda) |journal=[[Journal of Zoology]] |volume=236 |issue=4 |pages=697–706 |doi=10.1111/j.1469-7998.1995.tb02740.x}}</ref> although adults may decrease cannibalistic behaviour directed at juveniles when they are likely to encounter their own offspring.<ref>{{cite journal |first1=Susan E. |last1=Lewis |first2=Jaimie T.&nbsp;A. |last2=Dick |first3=Erin K. |last3=Lagerstrom |first4=Hazel C. |last4=Clarke |year=2010 |title=Avoidance of filial cannibalism in the amphipod ''Gammarus pulex'' |journal=[[Ethology (journal)|Ethology]] |volume=116 |issue=2 |pages=138–146 |doi=10.1111/j.1439-0310.2009.01726.x|bibcode=2010Ethol.116..138L }}</ref> In addition to age, sex may affect cannibalistic behaviour as males cannibalised newly moulted females less than males.<ref name="Dick"/>

They have, rarely, been identified as feeding on humans; in [[Melbourne]] in 2017 a boy who stood in the sea for about half an hour had severe bleeding from wounds on his legs that did not coagulate easily. This was found to have been caused by "sea fleas" identified as ''lysianassid amphipods'', possibly in a feeding group. Their bites are not venomous and do not cause lasting damage.<ref>{{Cite news |last=Zhou |first=Naaman |date=2017-08-08 |title=Australian teen just 'unfortunate' to be attacked by meat-loving sea fleas |url=https://www.theguardian.com/environment/2017/aug/08/australian-teen-just-unfortunate-to-be-attacked-by-meat-loving-sea-fleas |work=The Guardian |language=en-GB |issn=0261-3077 |access-date=2024-01-22}}</ref>

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