Occurrence of Haemoparasites of the Genus Hepatozoon (Adeleorina: Hepatozoidae) in the Marsh Frog (Pelophylax ridibundus Pallas, 1771) in Bulgaria

The distribution of species of Hepatozoon from anurans, specifically frogs, and their hostparasite relationships are of great interest. Due to the specifics of the ontogeny of frogs, they form a link between aquatic and terrestrial ecosystems. These amphibians are important in food chains, ensuring the normal functioning of biocenosis. In this study, we present data on the presence of Hepatozoon sp. in the marsh frog, Pelophylax ridibundus (Pallas, 1771) for the first time in Bulgaria. The blood smears of 137 individuals were investigated by fluorescence microscopy after staining with acridine orange. In three of five studied localities, the presence of apicomplexan haemoparasite from the genus Hepatozoon was revealed. Prevalence and parasitaemia values were different in frogs populations inhabiting the Chaya River (27.5% and 11.0%, respectively), Tsalapitsa Rice Fields (6.4% and 9.9%, respectively) and nature wetland Zlato pole (10.0% and 8.1%). It was found that the morphology and morphometric parameters of the parasite gamonts are closest to Hepatozoon magna, but molecular tools are required to confirm the genus and species determination. Our findings revealed that acridine orange is appropriate dye for detecting haemoparasites of the genus Hepatozoon.