Tyutin A.V.1, Medyantseva E.N.1, Tyutin V.A.2, Pavlov D.F.1, Makrushin A.V.1 2023. Communities of trematodes in Ponto-Azov gravel snail Lithoglyphus naticoides (C. Pfeiffer, 1828) Gastropoda: Hydrobiidae) and their potential impact on the development of marginal host populations in the Volga River basin // Invertebrate Zoology. Vol.20. No.2: 205–222 [in English].

1 Papanin Institute for Biology of Inland Waters Russian Academy of Sciences – IBIW RAS, Borok, 109, Nekouzskii Raion, Yaroslavl Oblast, 152742 Russia. E-mails: tyutin@ibiw.ru ; medyntseva@ibiw.ru ; makru@ibiw.ru

2 P.G. Demidov Yaroslavl State University, Sovetskaya str., 14, Yaroslavl, 150003 Russia.

doi: 10.15298/invertzool.20.2.05

ABSTRACT: Recently the prosobranch freshwater mollusk Lithoglyphus naticoides  successfully established in the Rybinsk and Uglich reservoirs and became a permanent element of the Upper Volga fauna. The present paper sets to study the characteristics of trematode communities in the colonies of L. naticoides, formed under relatively unfavorable habitat conditions for the host at the northeastern border of the range, and to characterize the host-parasite relations. We revealed the parthenitae of Apophallus muehlingi, Apophallus (=Rossicotrema) donicus, Parasymphylodora markewitschi, Nicolla skrjabini, Sanguinicola volgensis in the marginal populations of this invasive mollusk. Besides, we found Xiphidiocercaria sp., representing a new host record for L. naticoides in the Uglich Reservoir, the species identity of which has not yet been clarified. The possibility of using indicators of the occurrence of trematodes (the prevalence, P±SE, %) to assess the degree of pathogenic influence on this host and competitive relations between trematodes is studied. The results of statistical analysis of the data on the prevalence of parthenitae are confirmed by studies of the hepatopancreas of adult specimens of L. naticoides performed using histological methods. In particular, it is noticeable that even fully developed daughter rediae of Apophallus sp. exhibit weakest effect on the digestive gland of L. naticoides. The body of these very mobile rediae is relatively thin, and they easily move between the lobes of the hepatopancreas, practically without squeezing them. It is shown that the rediae of A. muehlingi, A. donicus, and P. markewitschi usually dominate at the initial stage of L. naticoides colony development. At the stage of full establishing of L. naticoides, the prevalence of N. skrjabini or S. volgensis sporocysts can increase quickly. Based on analysis of the data on the prevalence of parthenitae and histological examinations we assume that the small size of the digestive gland of L. naticoides prevents the full development of a mixed infection with parthenitae of two or more species. The maximum proportions of mixed infections were 6.87–8.82% of the total number of individuals studied. Of the six variants of double infection in the Upper Volga basin, the most common cases are Nicolla + Sanguinicola, Nicolla + Parasymphylodora, Sanguinicola + Parasymphylodora. Mixed infection with Apophallus + Parasymphylodora, Sanguinicola + Xiphidiocercaria, Parasymphylodora + Xiphidiocercaria is less common. For the populations of L. naticoides we studied, due to the short period of joint coevolution, during which the helminth adapted to this host, the trematode S. volgensis is considered to be the most pathogenic parasite, both at the organismic and at the population levels. The negative effect of the communities of trematodes sharply increases with an increase in the population density of S. volgensis.

KEY WORDS: alien species, Gastropoda, Lithoglyphus naticoides, marginal populations, parasites, Trematoda, mixed infections.

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