Species composition of helminths in lake frogs Pelophylax ridibundus (Pallas, 1771) in rivers of the Belgorod Region

The purpose of the research is to identify the species composition of helminths in lake frogs (Pelophylax ridibundus (Pallas, 1771)) caught in rivers of the Belgorod Region.Materials and methods. We studied frogs collected using a hydrobiological net in the rivers in fve Belgorod Region districts during the spring-summer 2016–2019. Species identifcation was performed according to morphological characteristics. The sex of the studied frogs was determined by gonads, and the age was determined based on size data. To assess infection of P. ridibundus with individual helminth species and their distribution, we used standard parameters for parasitological survey, namely, the prevalence, the amplitude of infection intensity, and the abundance index.Results and discussion. As a result of helminthological studies of 122 lake frogs, 17 helminth species were identifed which were widely specifc among representatives of the Ranidae family. Presumably, the identifed species form the basis of the species composition of frog helminths in rivers of the Region. Most of these types of helminths occur throughout the springsummer season without pronounced seasonal dynamics. It was noted that the number of helminth species simultaneously parasitizing in one frog increased with age. Opisthioglyphe ranae is the most often numerically dominant species in the examined areas of the Belgorod Region; and Diplodiscus subclavatus, Pleurogenes claviger and Codonocephalus urnigerus mtc have high abundance at some stations.