UDC 598.115.31:595.132(282.247.32-197.4) INFECTION OF DICE SNAKE, NATRIX TESSELLATA (REPTILIA, COLUBRIDAE), WITH EUSTRONGYLIDES EXCISUS (NEMATODA, DIOCTOPHYMATIDAE) IN THE MIDDLE AND LOWER DNIPRO RIVER BASIN S. V. Yermolenko1*, V. A. Gasso1, A. M. Hahut1, V. A. Spirina2 1Research Institute of Biology, Oles Honchar Dnipro National University, Gagarin av., 72, Dnipro, 49010 Ukraine 2Department of Microbiology and Immunology, Dalhousie University, 6299 South Street, Halifax, B3H 4R2, Nova Scotia, Canada *Corresponding author E-mail: yermolenko_sv@i.ua S. V. Yermolenko (https://orcid.org/0000-0001-5496-0910) V. A. Gasso (https://orcid.org/0000-0002-6094-9408) A. M. Hahut (https://orcid.org/ 0000-0001-7942-6490) V. A. Spirina (https://orcid.org/0000-0003-1336-8624) Infection of Dice Snake, Natrix tessellata (Reptilia, Colubridae), with Eustrongylides excisus (Nematoda, Dioctophymatidae) in the Middle and Lower Dnipro River Basin. Yermolenko, S. V., Gasso, V. Y., Hahut, A. M., Spirina, V. A. — Dice snakes can be a paratenic host for a stage IV of Eustrongylides excisus, Jägerskiöld, 1909 larva due to specific diet of the snakes. The infection rate of E. excisus in Natrix tessellata (Laurenti, 1768) was studied in the basin of the middle and the lower Dnipro River in 2013–2017. We searched for nematodes in snakes from four sites: Prydniprovska Thermal Power Station, Majorova Balka, Zaporizhzhia; National Nature Park Velykyi Luh. The snakes from all studied areas had high prevalence of infection (more than 90 %). The lowest level of intensity (2.50 ± 0.60) and abundance (2.27 ± 0.58) were in ecosystems near Prydniprovska ТPP. There was no significant difference between infection parameters in snakes from other groups. Capsules with larva localized in the gastrointestinal tract, liver, muscles, and lung. The most infected was the gastrointestinal tract statistical analysis showed significant differences with other organs. The lowest infection was found in the lung. Environmental pollution of the Dnipro River waters with pesticides and other pollutants accompanied by a climate change may influence on the E. excisus life cycle that needs additional studies. K e y w o r d s : eustrongylidosis, abundance, infection intensity, prevalence, Ukraine. Zoodiversity, 56(4):341-348, 2022 DOI 10.15407/zoo2022.04.341 Parasitology 342 S. V. Yermolenko, V. A. Gasso, A. M. Hahut, V. A. Spirina Introduction The nematode Eustrongylides excisus, Jägerskiöld, 1909 is one of the most common roundworm parasites in the Palearctic fish. Typical definitive hosts are fish-eating birds of the orders Ciconiiformes, Anseriformes, Gaviiformes and Pelecanoformes. Caspian seal and sturgeons may also be occasional final hosts (Fagerholm, 1996; Kornyushin et al., 2004; Goncharov, 2018; Rusconi et al., 2022). Because of bird defecation and regurgitation, the nematode eggs get into the water; oligochaetes of the genera Tubifex, Lumbricus, and Limnodrilus ingest it and the larval form of the helminth begins to develop. The next intermediate host is fish that feed on benthos, such as Gobiidae and Cyprinidae. Some species of predatory fish, amphibians and reptiles can be paratenic hosts for E.  excisus larvae at the third and fourth stages of development (Saglam & Arikan, 2006; Bjelić-Čabrilo et al., 2013). The nematode larvae of the third and fourth stages have also been detected in humans (Guardone et al., 2021; Honcharov et al., 2022). E. excisus began to be observed in fish of the middle and lower parts of the Dnipro River in the first half of the 2000s. There are some reports of infection of round goby Neogobius melanostomus (Pallas, 1814), European perch Perca fluviatilis Linnaeus, 1758, pikeperch Sander lucioperca (Linnaeus, 1758) and wels catfish Silurus glanis Linnaeus, 1758 (Yesipova, 2013; Rubtsova, 2015). This may be related to changes in hydrological and climatic conditions, which led to an increase in breeding numbers of fish-eating birds, such as great cormorant Phalacrocorax carbo (Linnaeus, 1758) (Bulakhov et al., 2007), for which E.  excisus is a common autogenous species (Bjelić-Čabrilo et al., 2013). The dice snake Natrix tessellata (Laurenti, 1768) occupies a large areal that extends from Central and Southern Europe to Western China and Southwestern India (Gruschwitz et al., 1999; Liu et al., 2011; Šukalo et al., 2014; Jablonski & Kautman, 2017). It is one of the most common snake species in Ukraine (Kotenko et al., 2011; Gasso et al., 2020; Baranovski et al., 2021). Despite the fact that the species is thermophilic, there is a tendency for N. tessellata to move northwards in Ukraine. The northernmost finds have been recorded in Kyiv Region. This may be due to an increase in the number of food items and an increase in the mean annual temperature (Nekrasova et al., 2013). The diet of N. tessellata is dominated by fish of the families Gobiidae and Cyprinidae, the species composition of which may differ from region to region (Acipinar et al., 2006; Luiselli et al., 2007; Göçmen et al., 2011; Bakiev et al., 2011, Hutinec & Mebert, 2011; Weiperth, 2014). If an E. excisus-in- fected fish is ingested, the dice snake becomes a paratenic host for a stage IV of E. excisus larva (Sharpilo, 1976). The aim of this study is to find out the degree of the dice snake infection in the ecosystems of the central and southern Dnipro River and determine the distribution of the nematode in the organs. Fig. 1. Location of the studied: 1 — Prydniprovska Thermal Power Station; 2 — Majorova Balka, 3 — Zaporizhzhia Сity; 4 — National Nature Park “Velykyi Luh”. Fig. 1. Location of the studied: 1 – Prydniprovska Thermal Power Station; 2 – Majorova Balka, 3 – Zaporizhzhia city; 4 – National Nature Park “Velykyi Luh”. 343Infection of Dice Snake, Natrix tessellata (Reptilia, Colubridae), with Eustrongylides excisus... Material and methods The research was conducted in 2013–2017. Sixty-five individuals of N.  tessellata from four sites were studied. They were collected at the middle part of the Dnipro River, namely, the natural coastal ecosystem of Majorova Balka (48.262° N, 35.169° E), the sanitary protection zone of Prydniprovska Thermal Power Plant (Dnipro City) (48.400° N, 35.113° E), and the coastal ecosystem of the Zaporizhzhia City (47.886° N, 35.134° E). Natural coastal ecosystem of the National Nature Park “Velykyi Luh” (NPP “Velykyi Luh”) (47.447° N, 35.133° E) is situated at the Kakhovske Reservoir, the lower part of the Dnipro River basin (fig. 1). The captured snakes were brought alive to the laboratory for processing. The reptile abdominal cavity was dissected by a longitudinal ventral incision. Internal organs were removed from the body cavity and the skin was separated from the muscle tissue for visual inspection. The organs were carefully dissected in Petri dishes filled with 0.9 % aqueous sodium chloride solution (Düşen, 2012). Identified helminths were fixed in hot 70 % ethanol (de Vasconcelos Melo et. al., 2016). After fixation, the nematodes were examined with the use of the Carl Zeiss Amplival Microscope. Species identification of helminths was carried out according to Sharpilo (1976). Prevalence, infection intensity and abundance index were calculated according to standard methods (Bush et al., 1997). The study was carried out in accordance with the “European Convention for the Protection of Vertebrate Animals used for Experimental and other Scientific Purposes” (Strasbourg, 1986) and Law of Ukraine No. 3447-IV “On the Protection of Animals from Cruelty” (Revision on August 8, 2021). Data statistical analysis was performed by calculating the mean (x) and standard error (SE) values. Nor- mality of distribution in the groups was carried out using the Shapiro-Wilk criterion. Nonparametric Kruskal- Wallis test was used for multiple comparisons of independent samples, and paired comparison was performed using Dunn’s test in case of statistically significant differences. Statistically significant differences were consid- ered at p < 0.05. Statistical analysis of the data obtained was performed using the Origin software, version 9.8 (Origin Lab Corp.). Results We found subcutaneous capsules located in the muscle tissue of the dorsal part of some dice snakes (fig. 2), which may be a manifestation of the snake infection by the nema- tode (Mihalca, 2011). The nematodes were also localised in connective tissue capsules on the surface of internal organs. Inflammation and mechanical damage to the organs have Fig. 2. Capsules with E. excisus larvae under the skin (A), on the gastrointestinal tract (B), on the liver (C), and on the musculature (D) of N. tessellata. 344 S. V. Yermolenko, V. A. Gasso, A. M. Hahut, V. A. Spirina sometimes been observed near the capsules. Up to three E. excisus larvae were found in one capsule; some of nematodes were dead. An inter-group comparison of infection intensity and abundance index of E. excisus larvae in dice snakes revealed some statistically significant differences. In all studied eco- systems, the prevalence of infection of the dice snakes was more than 80 %. In snakes from Zaporizhzhia, eustrongylidosis was detected in 100 % of investigated specimens. The lowest average intensity of infection was found in dice snakes from the population inhabited NNP Velykyi Luh. The average values of the infection intensity and helminth abundance index in N. tessellata from Prydniprovska TPP had the lowest values. A pairwise comparison of the infection indices of the dice snakes revealed significant differences between Prydniprovska TPP and all the other studied sites the snakes were collected from (p < 0.05) (table 1). Ex- cluding the Prydniprovska TPP, no significant differences were found between the sites in terms of E. excisus invasion and abundance in the dice snakes. A multiple comparison of the nematode abundance in the organs of snakes in all groups has been also revealed the significant differences. In the majority of the examined T a b l e 1 . E. excisus records for N. tessellata from sites of the middle and lower Dnipro River basin Site N P, % Intensity Abundance MI ± SE range MA ± SE Prydniprovska TPP 11 90.9 2.50 ± 0.60 a 1–7 2.27 ± 0.58a Majorova Balka 26 84.6 11.35 ± 2.25 b 1–43 9.38 ± 1.96b Zaporizhzhia 7 100 8.71 ± 2.39b 2–19 8.71 ± 2.39b NNP “Velykyi Luh” 22 90.9 14.85 ± 2.49b 1–36 14.45 ± 2.33b N o t e . P — prevalence; MI — mean intensity of infestation; MA — mean abundance; SE — standard er- ror. T a b l e 2 . Distribution of nematodes E. excisus in organs of N. tessellata from sites of the middle and lower parts of the Dnipro River basin Site Index Gastrointestinal tract Liver Muscles Lung Prydniprovska TPP (n = 11) x ± SЕ 2.00 ± 0.63a 0.09 ± 0.09bс 0.18 ± 0.12bc 0с min-max 0–7 0–2 0–1 0 P 81.8 9.09 18.2 0 Majorova Balka (n = 26) x ± SЕ 5.19 ± 1.11a 1.34 ± 0.66b 2.77 ± 1,35ab 0.08 ± 0.05с min-max 0-19 0-16 0-35 0-1 P 61.5 38.4 65.4 7.69 Zaporizhzhia (n = 7) x ± SЕ 5.86 ± 1.39a 1.14 ± 0.51bс 1.71 ± 0.61b 0c min-max 1–12 0–3 0–4 0 P 100 57.1 71.4 0 NNP “Velykyi Luh” (n = 22) x ± SЕ 9.91 ± 1.60a 1.91 ± 0.46b 2.27 ± 0.36b 0.36 ± 0.36c min-max 0–24 0–8 0–7 0–8 P 95.5 59.1 59.1 4.55 N o t e . P — prevalence, %; x — mean; SE — standard error; min-max — minimum and maximum num- ber of parasites in organs. 345Infection of Dice Snake, Natrix tessellata (Reptilia, Colubridae), with Eustrongylides excisus... dice snakes, more than half of the total number of nematodes were localised in the gastroin- testinal tract. Less than 8 % of the snakes from Majorova Balka (0.08) and NPP Velykyi Luh (0.36) were found to have capsules on the lung, in the snakes of other groups no E. excisus larvae were detected on that organ. In the studied snakes from the Prydniprovska TPP, Za- porizhzhia and NPP Velykyi Luh the most nematodes were found on the gastrointestinal tract and according to the Dunn’s test it differed from the abundance of the nematodes in other organs (p < 0.05). In snakes of Majorova Balka, no significant difference was found between the numbers of larvae in the muscular tissue (2.77) and in the gastrointestinal tract (5.19). Since in snakes from all studied ecosystems there are no significant differences between the nematode abundance in liver and muscles, it can be concluded that the distri- bution of nematodes in these organs is relatively even (table 2). Discussion In the studied ecosystems of the Dnipro River, E. excisus is a common helminth of the dice snakes, which should manifest a high infection of species that used as prey of the snake. Goncharov (2017) notes that in predatory fish, the nematodes are largely predominant in muscular tissue. Apparently, the distribution of E. excisus in the dice snake organs and predatory fish has a different pattern in specific tissues. A similar pattern of prevalence has also been reported for the dice snakes in Romania (85 %) (Mihalca et al., 2007). E.  excisus has not been detected in helminth communities of the dice snakes caught in the Volga region (Kirilov, 2011), Armenia (Sargsyan et al., 2016) and some regions of Central and Western Asia (Shakarboev et al., 1999; Yossefi et al., 2014) with the exception of Bursa province, Turkey (Yildirimhan et al., 2007). Only one infested individual of N. tessellata was found in the southern part of the Volga delta in 1953 (Dubinina, 1953) (table 3). Previous studies of the helminth fauna of the grass snake Natrix natrix (Linnaeus, 1758) from the ecosystems of the same Dnipro area have not detected E. excisus (Yermo- lenko et al., 2019) despite wide distribution and abundance of the snake species (Gasso, 2011). It is worth noting that cases of N.  natrix infection with this nematode species were recorded in Bursa province, but the infection of the grass snakes was quite low (1 of 21 examined individuals) (Yildirimhan et al., 2007). The possibility of infection exists be- cause bentophagous fish was observed in the diet of the grass snake (Hutinec & Mebert, 2011). In addition, the marsh frog Pelophylax ridibundus Pallas, 1771, which is known prey of N. natrix, is also possible host of E. excisus (Saglam & Arikan, 2006; Koyun et al., 2015). T a b l e 3 . E. excisus records for N. tessellata from different regions Region Quantity, no. of snakes Prevalence, % Mіn–Max Reference Romania 20 85 3–22 Mihalca et al., 2007 Mazandaran province, Iran 9 0 0 Yossefi et al., 2014 Angren River, Uzbekistan 100 0 0 Shakarboev et al., 1999 Armenia 16 0 0 Sargsyan et al., 2016 Bursa Province, Turkey 24 46 1–6 Yildirimhan et al., 2007 Volga River Basin, Russia 58 0 0 Bakiev et al., 2011 Seaside part of the Volga River Delta, Russia 12 8.33 0–1 Dubinina, 1953 South Bulgaria no data 9.1 2 Biserkov, 1996 Northeastern Bulgaria – 17 1–10 Kirin, 2002 346 S. V. Yermolenko, V. A. Gasso, A. M. Hahut, V. A. Spirina Presumably, unfavourable environmental conditions of the sanitary protection zone of Prydniprovska Power Plant may affect animal species included in the life cycle of the E. ex- cisus. The surface waters in the area of the Prydniprovska TPP location have a high-level pollution of oil products, phosphates and nitrates (Kroik & Dorhanova, 2016). Environ- mental pollution of the Dnipro River waters with pesticides and other pollutants (Zarubin, 2013; Strilets, 2018; Kurchenko & Sharamok, 2020) accompanied by a climate change may influence on the E. excisus life cycle peculiarities and on a place of the dice snake in it that needs additional specific research. References Acipinar, H., Gaygusuz, O., Tarkan, A. S., Gursoy, C., Al, Z. 2006. Presence of an invasive fish species Carassius gibelio (Bloch, 1782) in the diet of the dice snake, Natrix tessellata (Laurenti, 1768). Journal of Fisheries and Aquatic Science, 1 (2), 213–217. Bakiev, A., Kirillov, A., Mebert, K. 2011. Diet and parasitic helminths of dice snakes from the Volga Basin, Rus- sia. Mertensiella, 18, 325–329. Baranovski, B. A., Ivanko, I. A., Gasso, V. Y., Ponomarenko, O. L., Dubyna, D. V., Roshchyna, N. O., Karmyzo- va, L. O., Polevа, J. L., Nikolaieva, V. V. 2021. Biodiversity of the Regional Landscape Park Samara Plavni within the first large reservoir in Europe. Biosystems Diversity, 29 (2), 160–179. Biserkov, V. 1996. New records of Nematodes and Acanthocephalans from snakes in Bulgaria. Comptes rendus de l’Academie Bulgare des Sciences, 49 (1), 76–78. Bjelić-Čabrilo, O., Novakov, N., Ćirković, M., Kostić, D., Popović, E., Aleksić, N., Lujić, J. 2013. The first deter- mination of Eustrongylides excisus Jägerskiöld, 1909 larvae (Nematoda: Dioctophymatidae) in the pike- perch Sander lucioperca in Vojvodina (Serbia). Helminthologia, 50 (4), 291–294. Bulakhov, V. L., Gubkin, A. A., Ponomarenko, O. L., Pakhomov, O. Y. 2008. Biological Diversity of Ukraine. Dnipropetrovsk Region. Aves: Non-Passeriformes. Dnipropetrovsk University Press, Dnipropetrovsk [In Ukrainian]. Bulakhov, V. L., Gasso, V. Y., Pakhomov, O. Y., 2007. Biological Diversity of Ukraine. Dnipropetrovsk Region. Amphibians and Reptiles (Amphibia et Reptilia). Dnipropetrоvsk University Press, Dnipropetrovsk [In Ukrainian]. Bush, A. O., Lafferty, K. D., Lotz, J. M., Shostak, A W. 1997. Parasitology meets ecology on its own terms: Margolis et al. revisited. Journal of Parasitology, 83 (4), 575–583. de Vasconcelos Melo, F. T., do Nascimento, L. D. C. S., Macedo, L. C., dos Santos, J. N., Kuzmin, Y. 2016. The morphology of free-living stages and immature parasites of Rhabdias paraensis (Nematoda: Rhabdiasidae), a parasite of Rhinella marina (Anura: Bufonidae) in Brazil. Acta Parasitologica, 61 (1), 42–51. Dubinina, M. N. 1953. Dynamics of the parasite fauna of grass and dice snakes from the seaside area of the Volga delta. Studies of the Zoological Institute of Academy of Sciences USSR, 13, 171–190 [In Russian]. Düşen, S. 2012. First data on the helminth fauna of a locally distributed mountain frog, “Tavas frog” Rana tavasensis Baran & Atatür, 1986 (Anura: Ranidae), from the inner-west Anatolian region of Turkey. Turkish Journal of Zoology, 36 (4), 496–502. Fagerholm, H. P. 1996. Nematode parasites of marine-and shore birds, and their role as pathogens. Bulletin of the Scandinavian Society for Parasitology, 6 (2), 16–30. Gasso, V. Y. 2011. Grass snake populations’ features of the forest biogeocoenoses in the Samara river area. Visnyk of Dnipropetrovsk University. Biology, Ecology, 19 (2), 136–142. Gasso, V. Y., Hahut, A. N., Yermolenko, S. V., Hasso, I. A., Agca, C. A., Nedzvetsky, V. S., Sukharenko, E. V. 2020. Local industrial pollution induces astrocyte cytoskeleton rearrangement in the dice snake brain: GFAP as a biomarker. Biosystems Diversity, 28 (3), 250–256. Göçmen, B., Çiçek, K., Yildiz, M. Z., Atatür, M. K., Dinçaslan, Y. E., Mebert, K. 2011. A preliminary study on the feeding biology of the dice snake, Natrix tessellata, in Turkey. Mertensiella, 18, 365–369. Goncharov, S. L. 2017. Distribution of larvae of nematode Eustrongylides excisus Jägerskiöld, 1909 (Nematoda: Dioctophymatidae) in the body of predatory fish. Theoretical and Applied Veterinary Medicine, 5 (3), 5–9 [In Ukrainian]. Goncharov, S. L., Soroka, N. M., Pashkevich, I. Y., Dubovyi, A. I., Bondar, A. O. 2018. Infection of predatory fish with larvae of Eustrongylides excisus (Nematoda, Dioctophymatidae) in the delta of the Dnipro River and the Dnipro-Buh estuary in southern Ukraine. Vestnik Zoologii, 52 (2), 137–144. Guardone, L., Ricci, E., Susini, F., Polsinelli, E., Guglielmone, G., Armani, A. 2021. First detection of Eustrongylides excisus (Nematoda: Dioctophymatidae) in big-scale sand smelt (Atherina boyeri) from the lake Massaciuccoli (Northwest Tuscany, Italy): implications for public health and seafood quality. Food Control, 120, 107517. 347Infection of Dice Snake, Natrix tessellata (Reptilia, Colubridae), with Eustrongylides excisus... Gruschwitz, M., Lenz, S., Mebert, K., Lanka, V. 1999. Natrix tessellata (Laurenti, 1768) — Würfelnatter. In: Böhme, W., ed. Handbuch der Reptilien und Amphibien Europas, 3 (2). AULA-Verlag, Wiesbaden, 581–644. Honcharov, S. L., Soroka, N. M., Halat, M. V., Dubovyi, A. I., Zhurenko, V. V., Halushko, I. A. 2022. Distribution of the nematodes of the genus Eustrongylides (Nematoda, Dioctophymatidae) in the world. Regulatory Mechanisms in Biosystems, 13 (1), 73–79. Hutinec, B. J., Mebert, K. 2011. Ecological partitioning between dice snakes (Natrix tessellata) and grass snakes (Natrix natrix) in southern Croatia. Mertensiella, 18, 225–233. Kirin, D. 2002. New records of the helminth fauna of grass snake, Natrix natrix L., 1758 and dice snake, Natrix tessellata Laurenti, 1768 (Colubridae: Reptilia) in South Bulgaria. Acta Zoologica Bulgarica, 54, 49–53. Kornyushin, V. V., Smogorzhevskaya, L. A., Iskova, N. I. 2004. Circulation of helminthes in colonies of Pelicaniformes and Ciconiiformes in the south of Ukraine. Branta, 7, 241–277 [In Russian]. Kotenko, T. I., Shaitan, S. V., Starkov, V. G., Zinenko, O. I. 2011. The northern range limit of the dice snake (Natrix tessellata) in Ukraine and the Don River basin in Russia. Mertensiella, 18, 311–325. Koyun, M., Birlik, S., Sümer, N., Yildirimhan, H. S. 2015. Helminth fauna of Eurasian marsh frog, Pelophylax ridibundus (Pallas, 1771) (Anura: Ranidae) from Bingöl, Eastern Anatolia, Turkey. Biharean Biologist, 9 (2), 128–132. Kroik, A., Dorganova, L. 2016. Patterns of formation of hydrochemical of surface water in the area of the Dnieper thermal power station. Journal of Geology, Geography and Geoecology, 24 (2), 55–60. Kurchenko, V. O., Sharamok, T. S. 2020. The hematological parameters of the Prussian carp (Carassius gibelio, (Bloch, 1782)) under the Zaporizhian (Dnipro) Reservoir conditions. Turkish Journal of Fisheries and Aquatic Sciences, 20 (11), 807–812. Jablonski, D., Kautman, J. 2017. Melanism in Natrix tessellata (Serpentes: Colubridae) from Slovakia. Herpetology Notes, 10, 173–175. Liu, Y., Mebert, K., Shi, L. 2011. Notes on distribution and morphology of the dice snake (Natrix tessellata) in China. Mertensiella, 18, 430–436. Luiselli, L., Capizzi, D., Filippi, E., Anibaldi, C., Rugiero, L., Capula, M. 2007. Comparative diets of three populations of an aquatic snake (Natrix tessellata, Colubridae) from Mediterranean streams with different hydric regimes. Copeia, 2007 (2), 426–435. Mihalca, A. 2011. Parasitism in the Dice Snake (Natrix tessellata): a Literature Review. Mertensiella, 18, 255–271. Mihalca, A. D., Gherman, C., Ghira, I., Cozma, V. 2007. Helminth parasites of reptiles (Reptilia) in Romania. Parasitology Research, 101 (2), 491–492. Nekrasova, O. D., Gavris, G. G., Kuybida, V. V. 2013. Changes in the northern border of the home range of the dice snake, Natrix tessellata (Reptilia, Colubridae), in the Dnipro basin (Ukraine). Vestnik zoologii, 47 (5), 67–71. Rusconi, A., Prati, P., Bragoni, R., Castelli, M., Postiglione, U., Rigamonti, S., Sassera D., Olivieri, E. 2022. Oc- currence of Eustrongylides excisus (Nematoda: Dioctophymatidae) in European Perch (Perca fluviatilis) and Great Cormorant (Phalacrocorax carbo) in Lake Annone, Northern Italy. The Journal of Parasitology, 108 (2), 209–216. Saglam, N., Arikan, H. 2006. Endohelminth fauna of the marsh frog Rana ridibunda from Lake Hazar. Turkey. Diseases of Aquatic Organisms, 72 (3), 253–260. Sargsyan, N., Arakelyan, M., Danielyan, F. 2016. Infestation of dice snake Natrix tessellata (Laurenti, 1768) by helminths in Armenia. Biological Journal of Armenia, 68 (1), 89–91. Shakarboev, E. B., Kuchboev, A. E., Kamilova, Sh. I., Azimov, D. А. 1999. Helminthes of the tesselated shake Natrix tessellata in the fauna of Uzbekistan. Uzbekistan Biological Journal, 3, 48–51 [In Russian]. Sharpilo, V. P. 1976. Parasitic Worms of Reptilians of the Fauna of the USSR. Naukova Dumka, Kiev [In Russian]. Strilets, R. O. 2018. Regional Report on the State of Natural Environment in Dnipropetrovska Oblast for 2017. Department of Environmental and Natural Resources of the Dnipro Regional State Administration [In Ukrainian]. Šukalo, G., Đorđević, S., Gvozdenović, S., Simović, A., Anđelković, M., Blagojević, V., Tomović, L. 2014. Intra- and inter-population variability of food preferences of two Natrix species on the Balkan Peninsula. Her- petological Conservation and Biology, 9 (1), 123–136. Weiperth, A., Potyó, I., Puky, M. 2014. Diet composition of the dice snake (Natrix tessellata Laurenti, 1768) in the Danube River catchment area. Acta Zoologica Bulgarica, 7, 51–56. Yermolenko, S., Gasso, V., Hahut, A., Spirina, V. 2019. Helminth іnfracommunity of grass snake Natrix natrix (Reptilia, Colubridae) in differently transformed ecosystems. Conference: ComEc 2nd International Con- ference on Community Ecology (June 4–6, 2019, Bologna, Italy), 89. Yesipova, N. B. 2013. The spread of parasitic nematodes in fish Eustrongylides excisus Zaporozhye (Dni- pro) reservoir. Modern problems of theoretical and practical ichthyology. Materials of VI Interna- tional Ichthyological Scientific-Practical Conference (October 9–11, 2013, Ternopil, Ukraine), 86–88 [In Russian]. 348 S. V. Yermolenko, V. A. Gasso, A. M. Hahut, V. A. Spirina Yildirimhan, H. S., Bursey, C. R., Goldberg, S. R. 2007. Helminth parasites of the grass snake, Natrix natrix, and the dice snake, Natrix tessellata (Serpentes: Colubridae), from Turkey. Comparative Parasitology, 74 (2), 343–355. Yossefi, M. R., Nikzad, R., Nikzad, M., Mousapour, A., Ramazanpour, S., Rahimi, M. T. 2014. High helmintic infection of the European grass snake, Natrix natrix and the dice snake, Natrix tessellata (Serpentes: Colubridae) from Iran. Asian Pacific Journal of Tropical Disease, 4, 263–267. Zarubin, О. L., Zarubina, N. E., Gudkov, D. I., Volkova, Е. N., Beliaev, V. V., Kaglian, А. Е., Kostiuk, V. А., Maliuk, I. А., Nazarov, А. B., Belokon, А. S., Marenkov, О. N. 2013. Specific activity 137Cs at fishes of Ukraine. Current state. Nuclear Physics and Atomic Energy, 14 (2), 177–182 [In Ukrainian]. Received 22 June 2022 Accepted 3 August 2022