Morphological and molecular data for highly pathogenic avian parasite Erschoviorchis anuiensis sp. n. and phylogenetic relationships within the Opisthorchiidae (Trematoda).

Adult worms of Erschoviorchis anuiensis sp. n., parasites of the pancreas and liver of birds, were found by feeding the Muscovy ducks Cairina moschata dom. with freshwater fish (Phoxinus percnurus) from the Amur River basin (Russia). The trematodes obtained differ from the only previously known representative of the genus, E. lintoni by the large size of the ventral sucker, testes and ovary, the shape of the ovary (three-lobed vs irregular oval for E. lintoni), and the degree of vitellarium development (well-developed vitellarium with numerous follicles vs weakly developed vitelline fields for E. lintoni). In addition, genetic data were obtained for E. anuiensis sp. n., including nucleotide sequences of the ITS region and the 28S rRNA gene of nuclear DNA, and the mitochondrial сох1 gene. These data show that the genus Erschoviorchis is a sister group to the representatives of the genera Opisthorchis, Clonorchis, and Metorchis. At the same time, it did not cluster with species of Amphimerus, in which E. lintoni has sometimes been placed. The results of the study indicated that E. anuiensis sp. n., as well as E. lintoni, when it occurs in the pancreas, leads to significant associated pathological changes, manifested in an increase in size, changes of structure and tissue density.