Wandering the taxonomic mine-field: the Podocotyle species complex (Digenea: Opecoelidae).

This study focuses on the opecoelid genus Podocotyle, particularly the species in the northern European seas (White, Barents and Pechora), with additional data from few isolates from the Far East. The research combines molecular analyses (28S, 5.8S+ITS2 rDNA, and cox1 mtDNA) and morphological examinations. Molecular analyses suggested that there are most likely four species of Podocotyle in the northern European seas and three more in the Far East. Morphological redescriptions are provided for three northern European species: P. atomon, P. reflexa, and P. odhneri, with the latter recognized as a valid species. The study also verified the life cycle of P. atomon and identified Lacuna vincta (Littorinidae) as the first intermediate host for P. reflexa. In the Sea of Okhotsk, L. turrita is the first intermediate host for two apparently undescribed Podocotyle species. The results also highlight the morphological variability of P. atomon, emphasizing the need for an integrative approach in the taxonomy and biodiversity studies.