First finding of spirurid larva (Chromadorea, Spirurida) in the common European viper Vipera berus (Linnaeus, 1758) of the Russian fauna

The National park “Smolny” (Republic of Mordovia, Russia) is located in the Basin of Alatyr River, a second-order tributary of the Volga River. Favorable conditions are created for the development of helminths and infecting reptiles with them in floodplain biotopes. In 2018–2020 in this Protected Area we examined 25 individuals of the common viper Vipera berus (Linnaeus, 1758) by the method of complete helminthological dissection. We studied only road-killed vipers and reptiles killed by local residents. In total, eight species of helminths were registered in vipers: Leptophallus nigrovenosus, Telorchis assula, Alaria alata , larvae, Rhabdias fuscovenosa, Oswaldocruzia filiformis, Physocephalus sexalatus , larvae, Physaloptera clausa , larvae and Agamospirura minuta , larvae. Larva of spirurid nematodes Ph. sexalatus, Ph. clausa and A. minuta were recorded in the common viper for the first time in Russia. We found these nematode juveniles in walls and lining of stomach and intestine of snakes. We gave original drawings and morphological descriptions of these nematodes. Vipera berus was noted as a new host for Physaloptera clausa . Currently the helminth fauna of Vipera berus of the Russian fauna includes 15 species. Helminth infection of Vipera berus strongly depends on habitat and, especially, on the diet features. Snakes that live in dry habitats and feed on mouse-like rodents, as a rule, are weakly infested by helminths. Conversely, helminth infection is higher in vipers living in near-water habitats and feeding tailless amphibians. Participation of paratenic hosts in the helminth life cycles plays an important role in the distribution and preservation of parasites in the wild, and increases the invasion probability of the final hosts.