Diversity of European lissorchiid trematodes from fish and snail hosts with comments on the validity of the genusParasymphylodoraSzidat, 1943

Genetic markers, DNA sequences and karyotypes, of some European lissorchiid species from their intermediate and final hosts were obtained to clarify controversial data about their life cycles and taxonomy, and to reveal phylogenetic affinities. The life cycles of three species have been confirmed for the first time based on molecular data. Comparative analysis of internal transcribed spacer 2 (ITS2) and partial 28S rDNA sequences has undoubtedly proven that cercariaeum of type-species of the genusAsymphylodora,Asymphylodora tincae, develops in pulmonate snails,Anisus vortexandStagnicola palustris, but not in the genusBithynia. The faucet snail,Bithynia tentaculata, serves as the first intermediate host forParasymphylodora(=Asymphylodora)markewitschiandParasymphylodora parasquamosa; adults of both species were isolated from the common rudd,Scardinius erythrophthalmus. It has also been confirmed thatB. tentaculataserves as the second intermediate host forP. parasquamosa. Phylogenetic analysis supports the validity of the genusParasymphylodora. Two species,Parasymphylodora markewitschiandP. parasquamosa, with cercariaeum belonging to theParasquamosumgroup, are closely related and are being recovered as a well-defined evolutionary lineage in phylogenetic trees. A significant divergence betweenParasymphylodoraspp. andAsymphylodoraspp. was revealed. The diploid chromosome set ofP. markewitschiis composed of 14 chromosomes and does not show similarities with karyotypes of other lissorchiid species.Asymphylodora progeneticaandAsymphylodora tincaeshare the basal diploid value of the family, 2n = 20, and reveal very close morphology of the corresponding chromosome pairs. Karyotypic similarities of these species are in accordance with molecular phylogenetic data. Thus, the available molecular and cytogenetic data support the assignment ofP. markewitschiandP. parasquamosato a separate genus, meanwhile, the assignment ofA. progeneticato the genusParasymphylodorawas not justified.