Nekrasova, O., Y. Kuzmin, R. Svitin, O. Marushchak, M. Bolotov, J.-Y. Georges & T. Kuzmina

Spread of helminth parasites of water frogs of the Pelophylax esculentus complex (Amphibia: Anura) on the Black Sea shore, Odesa region, Ukraine, after the destruction of the Kakhovka dam in June 2023 . pp. 67-76.

Abstract. The destruction of the dam of the Kakhovka Hydroelectric Power Plant in June 2023 during the Russian full-scale invasion of Ukraine caused large-scale changes in the ecosystems of southern Ukraine, including the sudden influx of massive flooding of freshwater, chemicals, and living organisms into the brackish coastal zones of the northwestern Black Sea region. This event led not only to industrial pollution but also to the unpredictable displacement of numerous species, including endangered frogs from destroyed freshwater habitats into new ecosystems. One of the potential consequences of this displacement is the appearance of new helminth infections downstream, which may affect the structure of parasite communities and the health of native fauna. The present study aimed to identify the species composition and features of the helminth fauna of the Pelophylax esculentus complex (P. ridibundus and P. esculentus) collected on the coast of the Odesa region after the flooding. Between 6–26 June 2023, a total of 28 individuals of Pelophylax esculentus complex (17 P. ridibundus and 11 P. esculentus) found on the seashore after the flood were collected for parasitological analysis. A total of 22 helminth species were identified, including 15 trematodes, five nematodes, one cestode, and one acanthocephalan. Fourteen (63%) species were adult forms, while the remainder were larval stages. A total of 15582 parasite specimens were recorded, dominated by the metacercariae of Codonocephalus urniger and Tylodelphys excavata, which accounted for over 70% of all the parasite specimens. Species richness and abundance were higher in P. ridibundus (20 species) compared to P. esculentus (14 species). Infracommunities were more heterogeneous in P. esculentus, reflecting potential multiple origins of frog individuals from different populations upstream. The observed differences between the two host species may be related to their specific body size, ecological origin, and routes of displacement. The relatively high number of larval stages highlights the role of amphibians as intermediate and paratenic hosts for a wide range of internal parasites whose definitive hosts include birds, snakes, turtles, and mammals. These findings suggest a potential risk of parasite introduction into new ecosystems and emphasize the need for epizootiological monitoring under post-disaster conditions. Catastrophic hydrological events can serve as a mechanism for the transfer of both host species and their parasites, disrupting ecosystem stability and threatening local fauna. Helminthological monitoring in areas of ecological disasters is essential for detecting hidden consequences and for developing measures to conserve biodiversity.

Key words. Landscape transformation, animal health, amphibians, helminths, ecocide, warfare ecology.