Abstract

Crayfishes and other invertebrates were collected during 2010 to 2016 from 519 sites located in the river basins of the Adour, Charente, Dordogne, Garonne, Loire, Seine, Rhône and Sélune in France. North American species included Pacifastacus leniusculus at 255 sites, Faxonius limosus at 206 sites, Procambarus clarkii at 56 sites, and the endemic Austropotamobius pallipes at two sites. However, branchiobdellidans were only recorded from 100 sites with 23 of these being sampled more than once, resulting in a total of 127 collections.      The widely distributed western North American, P. leniusculus carried four of its endemic branchiobdellidan species: Cambarincola gracilis, C. okadai, Triannulata magna and Xironogiton victoriensis. X. victoriensis was found at the majority of sites, with C. okadai, C. gracilis, and T. magna at fewer locations. Although F. limosus was the second most numerous crayfish species collected, it did not carry any of its endemic North American branchiobdellidan species. However, it was found cohabiting with P. leniusculus at four sites but carried X. victoriensis at only one of these. European A. pallipes only occurred at two sites with individuals harboring X. victoriensis, although no cohabiting exotic crayfish were found. Crayfish were also absent from three sites where free-living X. victoriensis were recovered from substrate samples. Procambarus clarkii appeared at sites scattered across the country, while specimens with C. mesochoreus were restricted to the Adour drainage.      This study has shown the widespread distribution of exotic branchiobdellidans in the wild and the virtual extinction of endemic species in France. In addition, we have provided the first European record of T. magna, and the first record of C. mesochoreus in France; the latter being only the second recording in Europe. With this comprehensive survey of their crayfish hosts in France, monitoring future exotic range expansions and endemic contraction or extinction can be traced. These data will be available to authorities for future planning in maintaining healthy freshwater bodies by reducing the damaging effects caused by exotic crayfishes.