Comparative analysis of the helminth fauna of Apodemus flavicollis and Apodemus uralensis (Rodentia, Muridae) from the protected areas (European Russia)

Closely related animal species living in similar conditions can enter into competitive relationships. The study of parasitic worms of animal hosts living in the same habitats is of great interest. We conducted a comparative analysis of the parasitic worms of cohabiting mice Apodemus flavicollis and Apodemus uralensis in the Mordovia Nature Reserve and the National Park “Smolny” (European Russia) in 2018–2022. A total of 1457 individuals of the two mouse species were examined by the complete helminthological necropsy: 635 A. flavicollis and 822 A. uralensis. In total 17 species of parasitic worms were recorded, including five cestodes, four trematodes, and eight nematodes. We found that the species diversity of helminths is higher in A. uralensis. All 17 species of parasites were identified in this rodent. The helminth fauna of A. flavicollis is less diverse and represented by 10 parasite species, also characteristic of A. uralensis, including three tapeworms, two flukes, and five nematodes. Apodemus flavicollis and A. uralensis inhabit similar forest habitats and are characterized by an average degree of similarity in helminth composition. The identified differences in the helminth fauna may be associated with the food preferences of these mouse species and the features of their microhabitats. Infection of the two mice with shared helminth species varied among the protected areas studied. At some sampling sites, the infection of A. flavicollis turned out to be higher, at others – of A. uralensis, which is due to changes in the moisture content of the forest floor and a different number of food items (invertebrates) that are intermediate hosts of helminths. The data obtained confirm the partial overlap of ecological niches of sympatric forest rodents, mainly in the spatial and trophic components.