Search

Abstract: The freshwater gastropod mollusk Lithoglyphus naticoides(C. Pfeiffer, 1828) naturalized successfully in the Rybinsk Reservoir and in the Uglich Reservoir in 2005–2011 and 2013–2015, respectively. The aim of this work is to study the structure of trematode communities in settlements of L. naticoidesformed by 2019 in the upper parts of these water bodies. It is found that, in both reservoirs, the species composition of trematodes is similar and includes Apophallus muehlingi(Jägerskiöld, 1899), Apophallus(=Rossicotrema) donicus(Skrjabin et Lindtrop, 1919), Parasymphylodora markewitschiKulakowskaja, 1947, Nicolla skrjabini(Iwanitzky, 1928), and Sanguinicola volgensis(Razin, 1929). The density of L. naticoidesvaries from 30 to 50 ind./m2in the shallows of the Rybinsk Reservoir and from 50 to 520 ind./m2in the Uglich Reservoir, where the mollusk is found at the depth of 2–9 m. In August 2019, the prevalence of parthenitae varied at different degrees even in relatively flowing upper parts of the reservoirs similar in hydrological characteristics: Apophallusspp. (32.01 and 11.45%), P. markewitschi(9.14 and 7.63%), N. skrjabini(16.57 and 7.63%), S. volgensis(19.43 and 63.36%). In the Uglich Reservoir, Xiphidiocercariasp. (9.16%) has been recorded, though their species has not yet been determined. A single case of mixed infection with parthenitae of trematodes (Sanguinicola+ Nicolla) was recorded in the Rybinsk Reservoir in 2019. In the Uglich Reservoir, mixed infection with two species of parasites is more common (Parasymphylodora+ Xiphidiocercaria, Sanguinicola+ Xiphidiocercaria, Sanguinicola+ Parasymphylodora, Sanguinicola+ Nicolla). Owing to the high occurrence of some trematodes, L. naticoidesis able to have a significant impact on the ecosystems of reservoirs by the development of foci of the helminthoses even with a relatively low size of its populations.

Abstract: The Ponto-Azov gastropod mollusk Lithoglyphus naticoides(C. Pfeiffer, 1828) naturalized in the Uglich Reservoir relatively recently (in 2013–2015). The main objective of this study is a comparative analysis of the species diversity and structure of trematode communities in different biotopes occupied by L. naticoidesafter the initial phase of its spread in the upper section of this water body (downstream the city of Dubna), characterized by a complex hydrological regime. The approximate coordinates of the geographical center of the large settlement of L. naticoidesare 56°53′ N, 37°25′ E. It is found that, by 2019–2021, the average density of L. naticoidesin this colony reached a consistently high value of about 450 specimens/m2. Judging by the variability of shell height in adult mature L. naticoidesspecimens, even within the same colony, optimum habitat conditions for this mollusk differ significantly in different biotopes. In a comparative aspect, data from two main hydrobiological sampling locations are considered: in the open part of the reservoir and at the mouth of a large tributary—the Dubna River. It is shown that, at both locations, the species composition of trematodes in L. naticoidesis similar and includes, in particular, parthenitae of Apophallus muehlingi(Jägerskiöld, 1899), Apophallus(=Rossicotrema) donicus(Skrjabin et Lindtrop, 1919), Parasymphylodora markewitschiKulakowskaja, 1947, and Nicolla skrjabini(Iwanitzky, 1928). However, Sanguinicola volgensis(Razin, 1929), dominant in L. naticoidesin the open part of the reservoir, is not found in the sample of mollusks from the mouth of the Dubna River. At the mouth of the Dubna River, compared to the collection point in the open part of the reservoir, the contamination level with parthenitae of other species of trematodes was also significantly lower: for N. skrjabiniand P. markewitschi, it was lower by a factor of 7; for Apophallusspp., by a factor of 8; for Xiphidiocercariasp., by a factor of 13. The ratio of males to females among mature specimens of L. naticoidesturns out to be close to 1 : 1, which is usual for many freshwater mollusks. In general, the high occurrence (the infection prevalence—the proportion of infected specimens in the host sample P± SE, %) in the open part of the reservoir indicates the presence of prerequisites for serious outbreaks of helminthoses: Xiphidiocercariasp. (9.16 ± 2.52%), Apophallusspp. (11.45 ± 2.78%), P. markewitschi(7.63 ± 2.32%), N. skrjabini(7.63 ± 2.32%), S. volgensis(63.36 ± 4.21%). At the same time, according to the data obtained, further spread of L. naticoidesin some tributaries of reservoirs in the Upper Volga basin may not have such serious parasitological consequences.

Abstract: The freshwater gastropod mollusk Lithoglyphus naticoides(C. Pfeiffer, 1828) is one of the most successful alien species in water bodies of the Volga River basin. One of the negative consequences of its spread is range expansion of trematode species, some of which are highly pathogenic to fish and fish-eating birds and mammals. The aim of this study is to analyze the features of formation of the trematode fauna in settlements of L. naticoidesat the northeastern border of its range (Rybinsk Reservoir). It is found that the first permanent settlement of L. naticoidesformed in 2005–2010 in coastal shallow waters in the lower part of the Volga reach of the reservoir. The mollusk did not spread rapidly throughout the entire water area of the reservoir outside the Volga reach zone with relatively high mineral water content. However, in 2011–2019, a new large settlement of L. naticoideswas recorded in the upper fast-flow part of the Volga reach. A relatively low density of mature individuals in the settlements of L. naticoides(up to 50 ind./m2) allows at least five trematode species to complete their life cycle: Apophallus muehlingi(Jägerskiöld, 1899), Apophallus(=Rossicotrema) donicus(Skrjabin et Lindtrop, 1919), Parasymphylodora markewitschiKulakowskaja, 1947, Nicolla skrjabini(Iwanitzky, 1928), and Sanguinicola volgensis(Razin, 1929). The prevalence of parthenitae of certain species depends on the reservoir water level regime, although the overall infestation of L. naticoidescan exceed 90%. The slow-flowing lower part of the Volga reach is characterized by the dominance of P. markewitschiand trematodes of the genus Apophallus; the upper section, which is close to the river type, is dominated by N. skrjabiniand S. volgensis. In the future, in the Rybinsk Reservoir, we can expect naturalization of other trematode species associated with L. naticoideswithin its range.