Utente:Marrabbio2/Progetto Forme di Vita: differenze tra le versioni

Versione delle 11:17, 31 ott 2012

Versione delle 20:45, 13 nov 2012

Riga 1:

[[File:Anilocra gigantea on Pristipomoides filamentosus.tif|thumb|right|250px|L'[[Isopode]]''[[Anilocra gigantea]]'' mentre parassita un esemplare di ''[[Pristipomoides filamentosus]]'']]

I [[parassita|parassiti]] colpiscono i [[pesci]] così come tutte le altre classi animali.

I parassiti più numerosi sono i [[protozoi]], ma decine sono le specie di [[vermi]] ([[Nematoda|Nematodi]], [[Platyhelminthes|Platelminti]], [[Anellida|Anellidi e [[Trematoda|Trematodi]]), [[Dinoflagellata|Dinoflagellati]], alcune specie di [[celenterati]] ([[Myxozoa]]), [[crostacei]] [[Isopoda|isopodi]] e [[funghi]] (''[[Glugea]]'', fungo [[Microsporidia]])

[[Parasite]]s in fish are a natural occurrence and common. Parasites can provide information about host population ecology. In [[fishery|fisheries biology]], for example, parasite communities can be used to distinguish distinct populations of the same fish species co-inhabiting a region. Additionally, parasites possess a variety of specialized traits and life-history strategies that enable them to colonize hosts. Understanding these aspects of parasite ecology, of interest in their own right, can illuminate parasite-avoidance strategies employed by hosts.

Usually parasites (and pathogens) need to avoid killing their hosts, since extinct hosts can mean extinct parasites. Evolutionary constraints may operate so parasites avoid killing their hosts, or the natural variability in host defensive strategies may suffice to keep host populations viable.<ref name="Moyle615"/> Parasite infections can impair the [[courtship dance]] of male [[threespine stickleback]]s. When that happens, the females reject them, suggesting a strong mechanism for the selection of parasite resistance."<ref>Bronseth T and Folstad I (1997) [http://rparticle.web-p.cisti.nrc.ca/rparticle/AbstractTemplateServlet?calyLang=eng&journal=cjz&volume=75&year=1997&issue=4&msno=z97-073 "The effects of parasites on courtship dance in threespine sticklebacks: More than meets the eye?"] ''Canadian Journal of Zoology'', '''75''':589–594.</ref>

However not all parasites want to keep their hosts alive, and there are parasites with multistage life cycles who go to some trouble to kill their host. For example, some tapeworms make some fish behave in such a way that a predatory bird can catch it. The predatory bird is the next host for the parasite in the next stage of its life cycle.<ref>Milinski, Manfred M (1985) [http://www.ingentaconnect.com/content/brill/beh/1985/00000093/F0040001/art00022 "Risk of Predation of Parasitized Sticklebacks (Gasterosteus Aculeatus L.) Under Competition for Food "] ''Behaviour'', '''93''' (14): 203-216.</ref> Specifically, the tapeworm ''[[Schistocephalus solidus]]'' turns infected threespine stickleback white, and then makes them more buoyant so that they splash along at the surface of the water, becoming easy to see and easy to catch for a passing bird.<ref>LoBue, C. P. and M. A. Bell. 1993. [http://www.journals.uchicago.edu/doi/abs/10.1086/285568 "Phenotypic manipulation by the cestode parasite ''Schistocephalus solidus'' of its intermediate host, ''Gasterosteus aculeatus'', the threespine stickleback"] ''American Naturalist'' '''142''':725–735.</ref>

Other parasitic disorders, include ''[[Gyrodactylus salaris]]'', ''[[Ichthyophthirius multifiliis]]'', [[cryptocaryon]], [[Velvet (fish disease)|velvet disease]], ''[[Brooklynella hostilis]]'', [[Hole in the head disease|Hole in the head]], ''[[Glugea]]'', ''[[Ceratomyxa shasta]]'', ''[[Kudoa thyrsites]]'', ''[[Tetracapsuloides bryosalmonae]]'', ''[[Cymothoa exigua]]'', [[leech]]es, [[nematode]], [[Trematoda|flukes]], ''[[Platyhelminthes]]'', [[fish louse|carp lice]] and [[Salmon louse|salmon lice]]

==Note==

<references />

==Boh==

{{Tassobox

|nome=Nothobranchius