A phylogenetic assessment of Pronoprymna spp. (Digenea: Faustulidae) and Pacific and Antarctic representatives of the genus Steringophorus Odhner, 1905 (Digenea: Fellodistomidae), with description of a new species
In this study, we elucidated the phylogenetic position of a Pacific species Pronoprymna petrowi, a Caspian species Pronoprymna ventricosa, an Antarctic species of the genus Steringophorus, S. liparidis, and a new species of the same genus, S. occidentalipacificus sp. nov. The new species was found in a bathylagid fish Leuroglossus schmidti from the Sea of Okhotsk. Steringophorus occidentalipacificus sp. nov. is similar to S. congeri, and differs from it in the length of the body and the forebody, the shape of the testes, the sucker-ratio, the size of eggs and the extension of the caeca and the cirrus-sac. The 28S rRNA gene-based analyses supported a sister relationship between Pr. petrowi and Pr. ventricosa, and put the genus Pronoprymna into to the group of faustulids (sensu lato), which is nested within the Gymnophaloidea clade. Based on the results of these analyses, Steringophorus is identified as a paraphyletic taxon within the Fellodistomidae (Gymnophalloidea). Phylogenic reconstructions also support a morphologically identified sister relationship between S. liparidis and S. thulini and demonstrate a close relationship of S. occidentalipacificus sp. nov. with S. blackeri and S. pritchardae. The analysis of the nd1 gene sequences also confirmed the phylogenetic affinity of S. liparidis to S. thulini.
