Hitch me a ride: first report of the alien leech Helobdella octatestisaca in Europe associated with freshwater turtles

Abstract

There is a massive gap in our knowledge of the distribution, ecology, and impacts of alien leeches. Here, we report the observation of two alien Helobdella species (H. europaea and H. octatestisaca) found during a long-term monitoring programme conducted in Northern and Western Spain. The alien leeches were attached to European pond turtles (Emys orbicularis) and Mediterranean pond turtles (Mauremys leprosa). In total, 29 European pond turtles and 29 Mediterranean pond turtles were trapped, 36% of which presented leeches attached to their shells or body. We amplified the COI gene region to confirm the identity of the leeches and trace their origins. Helobdella europaea leeches were identified in the two localities sampled, confirming the expansion of the species across the Iberian Peninsula. Moreover, their sequences were identical to the ones reported from Australia, Hungary, Taiwan, South Africa, USA and Spain. The other leech species, H. octatestisaca was detected attached to other leeches only in one of the localities sampled, and was genetically identical to sequences reported from South Africa and USA. This finding represents the first record of this species in Europe.