SUMMARY
The helminthofauna of Bombina bombina (Linnaeus, 1761) has been studied to an unequal degree in different parts of the habitat. Thus, it has been studied in more detail in the west of its range (in the countries of central and eastern Europe) and in less detail in the center (in Belarus and Ukraine). There were few data on helminths of this host in the east of its range (in Russia). For the first time, an inventory of the helminthofauna in B. bombina was carried out for populations in the Volga River Basin. The results of our own research are presented and supplemented with information from other authors. We summarized scattered data on helminths from 390 specimens of amphibians collected over more than 40 years in the territory of five regions: Kaluga and Samara regions, the Republics of Mordovia, Tatarstan and Bashkortostan. The helminthofauna includes 21 species from three classes: Trematoda (15), Chromadorea (5) and Clitellata (1). For each species, we give the systematic position, localization, places of detection, geographical distribution and characteristics of the life cycle. The leech Helobdella stagnalis (Linnaeus, 1758) was first recorded in the European fire-bellied toad in Europe. Four species of trematodes are new to this amphibian species in Russia: Haematoloechus abbreviatus (Bychowsky, 1932), Paralepoderma cloacicola (Luhe, 1909), larvae, Tylodelphys excavata (Rudolphi, 1803), larvae and Astiotrema monticelli (Stossich, 1904), larvae. Another species of trematode – Strigea strigis (Schrank, 1788), larvae – was first recorded in this host within the boundaries of the Volga Basin. A specific parasite is the trematode Haematoloechus abbreviatus (Bychowsky, 1932). The number and composition of the species of helminths of the European fire-bellied toad vary in different regions; the structure of the helminth fauna is generally stable and includes three groups of species: adult and larval stages of trematodes, adult nematodes-geohelminths. The results of the study create a database for further population studies and contribute to the development of ideas about the distribution and formation of the amphibian helminth fauna in Europe, Russia and the Volga Basin.