Genetic characterization of the Psilotrema (Digenea: Psilostomatidae) genus by partial 28S ribosomal DNA sequences.

In the present study, we successfully amplified the 28S ribosomal DNA of 3 species of the Psilotrema genus (Psilotrema oschmarini Besprozvannykh, 2007, P. acutirostris Oschmarin, 1963 and P. simillimum Muhling, 1989) from the Russian Far East. The genetic divergence between these species was estimated, and the phylogenetic relationships of the Psilotrema genus and the Psilostomatidae family were inferred. The resulting data support the independent taxonomical status of P. oschmarini as a valid species in the Russian Far East. In spite of the considerable morphological differences between P. simillimum and P. acutirostris, these species are genetically very close to each other. Genetic distances, calculated from the pairwise comparison of two obtained clusters using transversions, show that Psilostomatidae is the most divergent family. Phylogenetic analysis revealed two clusters, which corresponds to family Psilostomatidae (basal cluster) and other Echinostomatoidea species.