We studied the trematode fauna in land birds from the Republic of Mordovia (European Russia) in 2018–2022. In total, we identified 16 digenean species in 45 species of birds from the orders Passeriformes, Piciformes, Caprimulgiformes and Falconiformes. The trematodes Phaneropsolus micrococcus and Morishitum polonicum were recorded for the first time in the birds’ parasite fauna of Russia. We obtained the first data on helminths in Hippolais icterina and Ficedula albicollis from Russia and in Coccothraustes coccothraustes from the Middle Volga region. New host records resulting from our study include Brachylaima mesostoma from Coccothraustes coccothraustes; Urogonimus macrostomus from Sylvia atricapilla, Ficedula albicollis, Ficedula hypoleuca and Acrocephalus palustris; Plagiorchis maculosus from Ficedula albicollis and Hippolais icterina; and Lyperosomum alaudae from Ficedula hypoleuca. The common parasite of rallid birds Leucochloridium holostomum is recorded for the first time from Turdus merula in Russia. Taking into account the newly obtained data, we carried out a review of trematodes in land birds of the Middle Volga region, of which the Republic of Mordovia is a part. Currently, the list of land bird digeneans in the Middle Volga region includes 56 species. Among all the studied land birds, members of the order Passeriformes have the richest trematode fauna (33 species). The diversity of trematodes found in passerines is due to the large number of both individuals and species studied and the variety of habitats and diet preferences of these land birds. Most of the identified trematode faunas (47 species) are obligate parasites of land birds. Nine species parasitize land birds accidentally and/or facultatively. In the Middle Volga area, the fauna of trematodes is the most diverse in land birds of the Nizhny Novgorod region, where 31 species are revealed. Fewer species of trematodes are identified in birds from the Bashkortostan (20), Mordovia (17) and Samara regions (15). For the birds of Chuvashia and Tatarstan, only eight and one species of trematodes are known, respectively. Six trematode species, found in land birds, have veterinary and medical significance as potential pathogens of dangerous helminthiases.

Nematodes of the genus Oswaldocruzia parasitise the small intestine of amphibians and reptiles. Their biodiversity remains unknown. We studied Oswaldocruzia nematodes from nine species of amphibians and reptiles (Pelophylax ridibundus, Rana arvalis, Rana temporaria, Bufo bufo, Lacerta agilis, Zootoca vivipara, Anguis fragilis, Natrix natrix, Vipera berus) at six localities in European Russia in 2018-2019. To identify their nematode species, we analysed the morphological characters traditionally used in the taxonomy of nematodes of this genus together with new molecular phylogenetic data. The results of partial sequencing and molecular phylogenetic analysis of CoxI mtDNA gene showed that all Oswaldocruzia specimens in this study belonged to the same species. We observed a broad morphological variability of nematodes both from different host species and from the same host individual. Morphological variation in nematodes from various host species could be host-induced, while that in nematodes from the same host individuals could be due to phenotypic plasticity of the species. Molecular data indicate that only one species of the genus Oswaldocruzia, O. filiformis s.l., which has a broad morphological variability, parasitises amphibians and reptiles in European Russia. The results of our study highlight the necessity of studying the diversity of morphologically similar Oswaldocruzia spp. from the Western Palearctic by molecular genetic methods.

Поступила в редакцию: 09.02.2017На территории Жигулевского заповедника изучена гельминтофауна 24 видов мелких млекопитающих (от-ряды Insectivora, Chiroptera, Rodentia). У микромаммалий отмечено 90 видов паразитов: Trematoda -24, Cestoidea -21, Nematoda -43 и Acanthocephala -2. Для каждого вида гельминтов указывается систематиче-ское положение, локализация, круг хозяев, место обнаружения, специфичность к хозяевам, географическое распространение. Наиболее богатой в видовом отношении гельминтофауной обладают грызуны, у которых зарегистрировано 33 вида паразитов. У рукокрылых отмечено 32 вида гельминтов; у насекомоядных -28 видов. Общим для всех трех отрядов млекопитающих является только один вид паразитов -скребень . В Волжском бассейне у мелких млекопитающих впервые найден 21 вид па-разитических червей. Из 90 видов гельминтов, зарегистрированных у микромаммалий Жигулевского запо-ведника, 9 имеют эпидемиологическое и эпизоотологическое значение.

The morphological and morphometric variability of the nematode Oswaldocruzia filiformis from ten amphibian species (Pelophylax ridibundus, Pelophylax lessonae, Pelophylax esculentus, Rana arvalis, Rana temporaria, Bufo bufo, Bufotes viridis, Pelobates vespertinus, Bombina bombina and Lissotriton vulgaris) was studied. The sampling was performed during the period of 2018–2020 in fifteen localities of European Russia. We examined the following morphological features: the number of crests in mid-body level, the shape of lateral alae, the shape of cephalic vesicle, shape and structure of spicules in males, the shape and structure of male caudal bursa, the shape and structure of the dorsal ray of bursa; and the measurements of nine morphometric characteristics in nematode females and seven characters in males, subjected to variability. Significant differences in the variability of morphometric characteristics of O. filiformis of both sexes in different amphibian species and amphibians from various regions were revealed. Likewise, significant differences were revealed for most of morphometric features of O. filiformis from amphibians of the same species from different regions of Russia. The type of male caudal bursa and the structure and shape of spicules were identical in all O. filiformis males studied. Likewise, we have not found variability in the structure of the reproductive system in O. filiformis females. Variability was noted in the shape and size of the cephalic vesicle and lateral alae, in the number at the mid-body level, in the shape and structure of the dorsal rib of male caudal bursa. Differences in morphometric characteristics of O. filiformis from amphibians of the same species from different regions of Russia can be explained by the phenotypic plasticity of the species. While variations in the nematode morphology from different amphibian species are caused by the host-induced morphological variability of the parasite. Differences in the size of nematodes and their morphology in different regions of Russia studied may be caused by changes in ecological conditions in amphibian habitats. The broad morphological variability of the nematode O. filiformis increases the adaptive capabilities of the helminth and allows it to parasitize a wide range of hosts.

The National park “Smolny” (Republic of Mordovia, Russia) is located in the Basin of Alatyr River, a second-order tributary of the Volga River. Favorable conditions are created for the development of helminths and infecting reptiles with them in floodplain biotopes. In 2018–2020 in this Protected Area we examined 25 individuals of the common viper Vipera berus (Linnaeus, 1758) by the method of complete helminthological dissection. We studied only road-killed vipers and reptiles killed by local residents. In total, eight species of helminths were registered in vipers: Leptophallus nigrovenosus, Telorchis assula, Alaria alata, larvae, Rhabdias fuscovenosa, Oswaldocruzia filiformis, Physocephalus sexalatus, larvae, Physaloptera clausa, larvae and Agamospirura minuta, larvae. Larva of spirurid nematodes Ph. sexalatus, Ph. clausa and A. minuta were recorded in the common viper for the first time in Russia. We found these nematode juveniles in walls and lining of stomach and intestine of snakes. We gave original drawings and morphological descriptions of these nematodes. Vipera berus was noted as a new host for Physaloptera clausa. Currently the helminth fauna of Vipera berus of the Russian fauna includes 15 species. Helminth infection of Vipera berus strongly depends on habitat and, especially, on the diet features. Snakes that live in dry habitats and feed on mouse-like rodents, as a rule, are weakly infested by helminths. Conversely, helminth infection is higher in vipers living in near-water habitats and feeding tailless amphibians. Participation of paratenic hosts in the helminth life cycles plays an important role in the distribution and preservation of parasites in the wild, and increases the invasion probability of the final hosts.