Morphological variability of Oswaldocruzia filiformis (Nematoda: Molineidae) in reptiles inhabiting the protected areas of the Republic of Mordovia (Russia)

The morphological variability of the nematode Oswaldocruzia filiformis Goeze, 1782 from five reptile species ( Lacerta agilis, Zootoca vivipara, Anguis fragilis, Natrix natrix, Vipera berus ) was studied in 2018-2020 in the Smolny National Park and the Mordovia State Nature Reserve. We analyzed the morphological characters traditionally used in the taxonomy of Oswaldocruzia spp. A wide morphological variability of nematodes has been found, both in different host species and within the same host species. Variation of the morphological characters of O. filiformis from different reptile species was due to the host-induced variability. The morphological variability of nematodes from the same host species could be due to the phenotypic plasticity of O. filiformis .