Helminth fauna of tailless amphibians (Amphibia: Anura) of the Usa river basin

For the first time data on the composition and structure of helminth fauna and the degree of helminth infection of amphibians of the Usa River basin, Samara region, are summarised. In the period from 1999 to 2023, 100 specimens of 4 species of tailless amphibians were examined by the method of complete helminthological autopsy: Pelophylax ridibundus, Rana arvalis, R. temporaria and Pelobates vespertinus. Twenty-one species of helminths of two classes, Trematoda (17) and Chromadorea (4), were recorded. The helminthofauna of Pelophylax ridibundus is the richest (20 species), the “core” of which consists of five trematode species: Skrjabinoeces similis, Opisthioglyphe ranae, Pleurogenes claviger, Pleurogenoides medians and Prosotocus confusus. The helminthofauna of Pelobates vespertinus (5 species), Rana arvalis and R. temporaria (1 each) is impoverished. The structure of the helminthofauna and peculiarities of infection by certain trematode species are of “river” character and are similar to those in the floodplain of the Sok River. On the coast of the Usinsky Bay, Pelobates vespertinus has a pathogenic trematode species Alaria alata (Goeze, 1782), which is the causative agent of alariasis, a dangerous helminthiasis of domestic and wild carnivores.