Editing Microphallus

{{short description|Genus of worms}}
{{For|the medical condition of having an unusually small penis|micropenis}}
{{italic title}}
{{Automatic Taxobox
| name = ''Microphallus''
| taxon = Microphallus
| authority = [[Henry Baldwin Ward|Ward]], 1901<ref>Ward H. B. (1901) "Notes on the parasites of lake fish III. On the structure of the copulatory organs in ''Microphallus'' nov.gen.". ''Tr. Amer. Micr. Soc.'' '''22''': 175-187.</ref>
| synonyms = ''Carneophallus''
| subdivision_ranks = Species
| subdivision = 
* ''[[Microphallus abortivus]]''
* ''[[Microphallus basodactylophallus]]''
* ''[[Microphallus bassodactylus]]''
* ''[[Microphallus breviatus]]''
* ''[[Microphallus claviformis]]''
* ''[[Microphallus fonti]]''
* ''[[Microphallus hoffmanni]]''
* ''[[Microphallus limuli]]''
* ''[[Microphallus nicolli]]''
* ''[[Microphallus opacus]]''
* ''[[Microphallus papillorobustus]]''
* ''[[Microphallus piriformes]]''
* ''[[Microphallus pirum]]''
* ''[[Microphallus primas]]''
* ''[[Microphallus pseudopygmaeus]]''
* ''[[Microphallus pygmaeus]]''
* ''[[Microphallus sabanensis]]''
* ''[[Microphallus similis]]''
* ''[[Microphallus turgidus]]''
}}
'''''Microphallus''''' is a [[genus]] of [[parasite|parasitic]] [[trematode]]s (flukes) in the family [[Microphallidae]]. The Greek name means "tiny [[penis]]".<!-- why? -->

== Hosts ==
They are parasitic on a variety of [[mollusc]]s, [[crustacean]]s, [[bird]]s, and [[mammal]]s, some species having complex life cycles involving more than one host.

For example, ''[[Microphallus piriformes]]'' parasitizes the rough periwinkle (''[[Littorina saxatilis]]''); when these are eaten by [[herring gull]]s it infects the bird and lays its eggs in the bird's feces to infect new periwinkles.

Other [[intermediate host]]s include, for example [[New Zealand mud snail]] ''Potamopyrgus antipodarum''<ref name="Osnas 2005"/><ref>Levri E. P. & Fisher L. M. (2000) "[http://sgnis.org/publicat/levrfish.htm The Effect of a Trematode Parasite (''Microphallus Sp.'') on the Response of the Freshwater Snail ''Potamopyrgus antipodarum'' to Light and Gravity] {{webarchive|url=https://web.archive.org/web/20050416201939/http://sgnis.org/publicat/levrfish.htm |date=2005-04-16 }}". ''Behaviour'' '''137'''(9): 1141-1151.</ref> and others.

== Parasite-host interactions ==
Several species are notable for manipulating or influencing their hosts. ''[[Microphallus piriformes]]'' causes its host, the rough periwinkle, to move upwards, making it more vulnerable to predation by [[herring gull]]s. ''[[Microphallus pseudopygmaeus]]'' [[chemical castration|chemically castrates]] ([[parasitic castration]]) its host, the snail ''[[Onoba aculeus]]'', and causes it to grow larger than normal (it is not clear if this gigantism benefits the host or parasite or if it is a non-adaptive side-effect).<ref>Gorbushin A. M. & Levakin I. A. (1999) "[https://www.angelfire.com/sc/gorbushin/pap99.html The effect of Trematode parthenitae  on the growth of ''Onoba aculeus'', ''Littorina saxatilis'' and ''L. obtusata''  (Gastropoda: Prosobranchia)]". ''J. Mar. Biol. Ass. UK'' '''79''': 273–279.</ref> ''[[Microphallus papillorobustus]]'' causes its host, the lagoon sand [[shrimp]] (''[[Gammarus insensibilis]]'') to swim upwards, making it more vulnerable to predation.<ref>Thomas F., Fauchier J. & Lafferty K. D. (2002) "[http://www.werc.usgs.gov/chis/Thomas_BES.pdf Conflict of interest between a nematode and a trematode in an amphipod host: test of the "sabotage" hypothesis]". ''Behav. Ecol. Sociobiol.'' '''51''': 296-301.</ref> Some species of this genus "hitch-hike" on the manipulations of other species; for example, ''[[Microphallus hoffmanni]]'' parasitizes the same sand shrimps as ''Microphallus papillorobustus'' but does not manipulate the shrimps itself, instead benefiting from the latter's manipulation of the host.

== Life cycle ==
An [[undescribed species|undescribed]] ''Microphallus'' species is a widespread and locally common parasite in New Zealand lakes and streams. Multilocus [[allozyme]] genotype data show that this ''Microphallus'' is a single outbred species with high levels of gene flow among South Island populations. The parasite exclusively uses ''[[Potamopyrgus antipodarum]]'' as the intermediate host, and the final hosts are [[waterfowl]]. Embryonated ''Microphallus'' eggs are ingested from sediment and hatch in the [[Reproductive system of gastropods|snail's gut]], penetrate the intestine, and migrate to the [[Reproductive system of gastropods|gonads]] and [[digestive gland]]. Following successful establishment, the parasite then undergoes [[asexual reproduction]], replacing much of the host's reproductive tissue and digestive gland, which results in complete sterilization of the snail. The first visible parasite developmental stages ([[blastocercariae]]) are detectable after approximately 75 days post-exposure and [[metacercaria]]e are common by 90 days post-exposure at 16&nbsp;°C in the lab. The life cycle is completed when snails containing metacercariae are consumed by waterfowl.<ref name="Osnas 2005"/>

==References==
The article incorporates CC-BY-2.0 text from reference.<ref name="Osnas 2005">Osnas E. E. & Lively C. M. (31 May 2005) "Immune response to sympatric and allopatric parasites in a snail-trematode interaction". ''[[Frontiers in Zoology]]'' '''2''': 8. {{doi|10.1186/1742-9994-2-8}}</ref>
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[[Category:Plagiorchiida genera]]