Morphological and molecular data on Pseudozoogonoides ugui Shimazu, 1974 (Digenea: Microphalloidea: Zoogonidae) ex Pseudaspius hakonensis (Günther, 1877) and taxonomic problems in Zoogoninae genera.

New morphological and molecular data were generated for trematodes recovered from the intestines of the fish Pseudaspius hakonensis from two locations in the south of the Russian Far East. Morphologically, these trematodes are identical to Pseudozoogonoides ugui (Microphalloidea: Zoogonidae) from Japan. According to results of phylogenetic analysis based on 28S rDNA sequence data, P. ugui was closely related to Zoogonoides viviparus, and P. subaequiporus appears as a sister taxon to these two species. Genetic distance values, calculated based on both 28S rDNA and ITS2 rDNA, between P. ugui and Z. viviparus represents an interspecific differentiation level. Our results have an ambiguous explanation, indicating that the implication of the presence of one or two compact vitellarial aggregations for the differentiation of Zoogonoides and Pseudozoogonoides should be reconsidered or that our results open up the question of the taxonomical status of trematodes previously denoted as Z. viviparus and P. subaequiporus.

Neodiplostomum cf. seoulense (Seo, Rim, Lee, 1964) sensu Pyo et al., 2014 (Trematoda: Diplostomidae Poirier, 1886): morphology, life cycle, and phylogenetic relationships.

Furcocercariae of the genus Neodiplostomum Railliet, 1919 (Diplostomidae Poirier, 1886) were found in freshwater snails Helicorbis sujfunensis Starobogatov, 1957 (Planorbidae Rafinesque, 1815) collected from three localities in the Russian southern Far East. For the trematodes from each locality, frogs played the role of the second intermediate host, and rats were the definitive host. Chickens were insusceptible to infection. The morphological and molecular data obtained for these trematodes indicated they were representatives of the same species. The experimentally-derived adult individuals were morphometrically similar to the East Asian Neodiplostomum seoulense (Seo, Rim, Lee, 1964), Neodiplostomum oriolinum Oschmarin, 1963, Neodiplostomum leei Chai and Shin, 2002, and Neodiplostomum boryongense Shin et al., 2008. Analysis of available data on the life cycle, developmental stage morphology, and molecular genetic characteristics of East Asian Neodiplostomum revealed a lack of information for objective assessment of the species status of neodiplostomula found in the East Asia region. Based on the considerations above and the data for the cox1 marker, we named the trematode Neodiplostomum cf. seoulense (Seo, Rim, Lee, 1964) sensu Pyo et al., 2014. In a phylogenetic reconstruction based on nuclear and mitochondrial markers, neodiplostomulas clustered into geographically related groups: South American, North American, European, and East Asian, with the former occupying an external position in the tree, which may indicate South America as a center of Neodiplostomum speciation.

Stephanoprora amurensis sp. nov., Echinochasmus milvi Yamaguti, 1939 and E. suifunensis Besprozvannykh, 1991 from the Russian southern Far East and their phylogenetic relationships within the Echinochasmidae Odhner 1910.

Mature worms of Stephanoprora amurensis sp. nov. were obtained in an experimental study of its life cycle. In the Russian southern Far East, this trematode circulates using freshwater snails Parajuga subtegulata, freshwater fish and birds as the first, second intermediate and final hosts, respectively. Stephanoprora amurensis sp. nov. differs from the well-known representatives of Stephanoprora in a number of morphometric indicators of the developmental stages. The validity of the species was also confirmed by nuclear and mitochondrial DNA markers. In addition, new genetic data were obtained for Echinochasmus suifunensis and Echinochasmus milvi. An analysis of phylogenetic relationships within Echinochasmidae based on the 28S rRNA gene and ITS2 region identified two clusters, one of which combines species of Echinochasmus with 20-22 collar spines and short-tailed cercariae, and the other which includes Stephanoprora spp. and a number of representatives of Echinochasmus with 24 collar spines and long-tailed cercariae. The results of phylogenetic analysis based on ITS2 data show interfamily level of differences between the two clusters and intergeneric differentiation between the three subclusters uniting the species of Stephanoprora and Echinochasmus.