Pleistophora mulleri
This microsporidian is a specialist parasite that replicates in the cells of the abdominal muscle of the freshwater amphipod Gammarus duebeni. Although it was initially found in the Irish sub-species G. d. celticus (Terry et al. 2003), an extended survey evidenced its presence in other sub-species of G. duebeni in Europe (Ironside et al. 2008). Infections by P. mulleri were found to reduce foraging abilities of G. d. celticus on smaller amphipod species and to increase predation risk by larger amphipods. Accordingly, the microsporidian can affect invasion process by reducing the predation of G. d. celticus on smaller invading species such as Crangonyx pseudogracilis, and to increase predation of infected individuals by larger invaders, such as G. pulex (Fielding et al. 2005).
It is only known to be transmitted between individuals through cannibalism (MacNeil et al. 2003). By comparing selectivity of cannibalism between infected and non-infected individuals, Bunke et al. (2015) showed the parasites to alter host behaviour. Indeed, healthy gammarids avoid preying on infected conspecifics while this is not the case for infected individuals. Although it is not clear if this alteration of host behaviour is adaptive or not for the parasite, the authors suggest it to be a by-product of infection, rather than a manipulation. Yet, the effects of cannibalism and of its alteration by P. mulleri on the invasion of C. pseudogracilis and G. pulex remain to be explored.
source for picture: http://cdn4.sci-news.com/images/2015/03/image_2618-Gammarus-duebeni-celticus.jpg
