First data on the Hirudinea fauna of lotic ecosystems of the Khanty-Mansi Autonomous Area (Russia).

Hirudinea, a small and ecologically important group of aquatic organisms, is poorly studied in northern Eurasia. In this study, we demyth the idea of the faunistic poverty of this region and present the first findings of rheophilic leeches from the Khanty-Mansi Autonomous Area, Russia. Investigation of 25 rivers (Severnaya Sosva, Ob, Konda-Irtysh, and Bolshoi Yugan river basins) resulted in finding 10 leech species with parasitic and non-parasitic life strategies. These species belong to two orders (Rhynchobdellida and Arhynchobdellida), three families (Glossiphoniidae, Piscicolidae, and Erpobdellidae) and six genera (, , , , , and ). Five species, , , , , and potentially new morphological species of piscine leeches sp., have been discovered for the first time in Western Siberia. Data on species diversity of rheophilic leeches include the exact systematic position for all leech taxa. Each species from the list is supplemented with information about its geographical distribution.