The Ponto-Caspian parasite Plagioporus cf. skrjabini reaches the River Rhine system in Central Europe: higher infestation in the native than in the introduced Danubian form of the gastropod Theodoxus fluviatilis

Abstract The introduction of non-indigenous organisms in new areas the context host-parasite interactions is still poorly understood. This study aimed at a parasitological and histopathological comparison two phylogenetically distinct forms freshwater snail Theodoxus fluviatilis River Rhine system: native Northern-European form, which showed decline for unknown reasons nowadays extinct Rhine, Danubian was introduced via Main–Danube canal. We histopathologically examined populations T. from three smaller rivers system after confirming phylogenetic background respective population genetically. Results differences prevalence trematodes histopathologic organic alterations between forms. Both were infected with an opecoelid trematode Plagioporus cf. skrjabini , whereby its significantly higher than form. parasitic is, to our knowledge, species system, presumably co-introduced through invasion second intermediate final hosts, i.e. Ponto-Caspian amphipods gobies. Its impact on needs be subject future studies.