Introduction and invasion of the red-eared slider and its parasites in freshwater ecosystems of Southern Europe: risk assessment for the European pond turtle in wild environments

The North American red-eared slider Trachemys scripta elegans, which is nowadays considered among the world's worst invasive species, could constitute a real threat to native freshwater turtles. Because this species shares the same habitats of the European pond turtle Emys orbicularis since its introduction in the European wetlands, we surveyed populations of both alien and indigenous species in France and Spain in order to determine the diversity of platyhelminth parasites (Monogenea, Polystomatidae) in natural environments and to evaluate the levels of risks associated with parasitism. DNA barcoding procedure based on partial cytochrome c oxydase I sequences revealed ten monogenean parasite species within E. orbicularis populations and/or captive animals among which at least eight could be considered as introduced parasites from American freshwater turtles. Results indicated that host switching could have occurred either in natural environments or in captivity, when indigenous turtles were kept with exotic species, demonstrating that captive turtles could act as reservoirs of parasites. The presence of non-native parasite species within wild populations of E. orbicularis in the European freshwater ecosystems also highlighted the risks that these parasites may pose on the survival of natural turtle's populations and on the dynamics of native parasites.