Trematodes of Lymnaea stagnalis (Linnaeus, 1758) in the water bodies of Lviv and its surroundings (Ukraine)

Background. This publication highlights the results of studies on the trematode fauna of Lymnaea stagnalis (Linnaeus, 1758) in the water bodies of Lviv and its surroundings. It was established that L. stagnalis is an important component of local biodiversity and can serve as an indicator of environmental conditions. From a practical perspective, the research enables the detection of trematode species hazardous to humans and animals within the study area, the identification of local foci of trematodiasis, and provides data for ecological monitoring of aquatic ecosystems. Materials and Methods. The study of the trematode fauna of L. stagnalis was conducted from June to August 2022 in five water bodies of Lviv and its surroundings, including Sand Lakes (Lviv), Black Lake (Sknyliv, Lviv District), the lake on Sadova Street (Sokilnyky, Pustomyty District), the pond on Krymska Street (Lviv), and the lake in the “Znesinnia” Park (Lviv). Molluscs were collected manually or using a dip net. During the study, 250 specimens of L. stagnalis were examined, and 750 temporary preparations of parthenitae were prepared for species identification. The intensity of invasion was determined during the helminthological dissection of molluscs. Statistical data analysis was performed using Statistica 8.0 and Excel software. Results. The trematode fauna of L. stagnalis in water bodies within the city and suburbs of Lviv, characterized by partial anthropogenic impact, abundant macrophytes, and favorable conditions for mollusc development, was studied. In the Sand Lakes, larvae of 10 trematode species were identified, 10 species in Black Lake, 8 in the lake on Sadova Street, 10 in the pond on Krymska Street, and 6 species in the lake of “Znesinnia” Park. The identified digeneans belonged to 8 families: Echinostomatidae, Notocotylidae, Plagiorchiidae, Strigeidae, Diplostomidae, Haematoloechidae, Schistosomatidae, and Telorchiidae. Conclusions. The species composition of the trematode fauna of L. stagnalis in the water bodies of Lviv and its surroundings comprises 14 species. The family Echinostomatidae exhibited the highest species richness. The most frequently encountered species were Notocotylus attenuatus (Rudolphi, 1809) and Trichobilharzia ocellata (La Valette, 1855). The prevalence of L. stagnalis infestation in the studied water bodies ranged from 42 % to 36 %, with the highest rates observed in the lake on Sadova Street (Sokilnyky) and the lowest in the Sand Lakes of Lviv. The presence of molluscs, waterfowl, fish, and macrophytes in the water bodies creates conditions for trematode circulation.