Acanthocephalan Parasites Reflect Ecological Status of Freshwater Ecosystem

Acanthocephalans’ position in food webs, in close interaction with free-living species, could provide valuable information about freshwater ecosystem health through the viability of the parasites’ host populations. We explored Pomphorhynchus laevis cystacanths’ and adults’ cumulative abundances, and prevalence of infection respectively in their Gammarus pulex intermediate hosts and Squalius cephalus definitive hosts in a Mediterranean river. First, we analysed the relationship between P. laevis cumulative abundances, its two hosts populations and the other acanthocephalan species found ( Pomphorhynchus tereticollis and Polymorphus minutus ). Second, we characterised the influence of bacteriological, physicochemical and biological water parameters on these acanthocephalans, and their intermediate and definitive hosts. This research highlights that P. laevis infection and cumulative abondance were closely related to their two hosts population in the river. Moreover, Pomphorhynchus sp. cumulative abundances were positively correlated with organic pollution in the river but negatively correlated with biodiversity and with ecological indexes of quality. Pomphorhynchus laevis species could thus benefit from moderate freshwater pollution, which promotes their tolerant intermediate and definitive hosts.