Oswaldocruzia Filiformis Sensu Lato (Nematoda: Molineidae) From Amphibians And Reptiles In European Russia: Morphological And Molecular Data

Nematodes of the genus Oswaldocruzia parasitise the small intestine of amphibians and reptiles. Their biodiversity remains unknown. We studied Oswaldocruzia nematodes from nine species of amphibians and reptiles (Pelophylax ridibundus, Rana arvalis, Rana temporaria, Bufo bufo, Lacerta agilis, Zootoca vivipara, Anguis fragilis, Natrix natrix, Vipera berus) at six localities in European Russia in 2018-2019. To identify their nematode species, we analysed the morphological characters traditionally used in the taxonomy of nematodes of this genus together with new molecular phylogenetic data. The results of partial sequencing and molecular phylogenetic analysis of CoxI mtDNA gene showed that all Oswaldocruzia specimens in this study belonged to the same species. We observed a broad morphological variability of nematodes both from different host species and from the same host individual. Morphological variation in nematodes from various host species could be host-induced, while that in nematodes from the same host individuals could be due to phenotypic plasticity of the species. Molecular data indicate that only one species of the genus Oswaldocruzia, O. filiformis s.l., which has a broad morphological variability, parasitises amphibians and reptiles in European Russia. The results of our study highlight the necessity of studying the diversity of morphologically similar Oswaldocruzia spp. from the Western Palearctic by molecular genetic methods.