Editing Microphallus (section)

== 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.