Diversity of Helminths of Reptiles (Serpentes and Lacertilia) in the Middle Volga Region (European Russia)

This paper presents an analysis of helminth diversity in reptiles in eight provinces of the Middle Volga region (European Russia) based on the dataset recently published in the GBIF as the Darwin Core Archive. The dataset contains up-to-date information on the occurrence of parasitic worms in lizards and snakes and summarizes the records obtained during long-term helminthological studies conducted in 1996–2024. It includes 8576 helminth occurrence records in nine reptile species inhabiting the Middle Volga region. All helminth occurrence records are georeferenced. In total, we present data on 45 parasitic worm species, including 4 species of cestodes, 21 species of trematodes, 16 species of nematodes, and 4 species of acanthocephalans. The richest helminth fauna was found in <i>Natrix natrix</i> (26 species), <i>Lacerta agilis</i> (21), <i>Natrix tessellata</i> (16), and <i>Vipera berus</i> (15). Less diverse is the helminth fauna in <i>Anguis colchica</i> (8 species), <i>Zootoca vivipara</i> (7), <i>Vipera renardi</i> (6), <i>Coronella austriaca</i> (5), and <i>Eremias arguta</i> (3). The diversity of helminths in reptiles of the Middle Volga region does not reach its maximum compared to other European countries. Most helminth species found in lizards and snakes of the studied region belong to the Palearctic faunal complex (25 species). Eight species of parasites have a Holarctic distribution. Seven helminth species parasitize reptiles only in Europe. Five species of parasites are cosmopolitan. Of the 45 species of helminths found in reptiles, 3 species have medical and veterinary significance as causative agents of dangerous helminthiasis. Data on the diversity and distribution of parasitic worms in reptiles of the Middle Volga region remain incomplete, so further observations may provide new occurrence records of helminths and expand the knowledge about their hosts.