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.
Для особо охраняемых природных территорий (ООПТ) отмечается высокий уровень биологического разнообразия, в том числе и у земноводных. Большой интерес вызывает группа европейских зеленых лягушек, характеризующаяся уникальным характером генетического и экологического взаимодействия в процессе гибридогенного воспроизводства. Приведены результаты исследований 2000-2018 гг. в пяти заповедниках (Мордовский, Присурский, Жигулевский, Волжско-Камский, Приволжская лесостепь) и четырех национальных парках (Смольный, Самарская Лука, Чаваш Вармане, Бузулукский бор). Изучаемые заповедники и национальные парки расположены в зоне перекрывания ареалов прудовой (Pelophylax lessonae) и озерной (P. ridibundus) лягушек, т.е. в районе потенциального распространения съедобной лягушки (P. esculentus), мероклонального гибрида, произошедшего от скрещивания указанных выше двух родительских видов. Выявлено, что озерная лягушка обитает во всех обследованных заповедниках и национальных парках, тогда как прудовая только в семи, а съедобная в пяти ООПТ. При изучении молекулярно-генетической изменчивости были использованы два маркера: для митохондриальной ДНК -фрагмент первой субъединицы гена цитохромоксидазы (COI), а для ядерной ДНК -интрон 1 гена сывороточного альбумина (SAI-1). Установлено, что в Среднем Поволжье у озерной лягушки встречаются митотипы и аллели двух криптических форм -«западной» (P. ridibundus) и «восточной» (P. cf. bedriagae). На ООПТ у этого вида были выявлены четыре из шести возможных комбинаций гаплотипов и аллелей по митохондриальной и ядерной ДНК, характерных для этих двух форм. Съедобная лягушка, обитающая на ООПТ, представлена только одним генотипом из четырех, обнаруженных в регионе. Популяционные системы зеленых лягушек на ООПТ представлены шестью типами. Здесь преобладают одновидовые популяции, включающие только озерную (n = 16; 41.0%) или прудовую (n = 10; 25.6%) лягушек. Среди смешанных популяционных систем чаще других отмечался тип, в котором представлены все три вида лягушек (n = 6; 15.4%). Реже встречаются системы, состоящие из двух видов: озерная и прудовая лягушки (n = 3; 7.7%), съедобная и прудовая (n = 3; 7.7%), озерная и съедобная (n = 1; 2.6%).Ключевые слова: Pelophylax ridibundus, Pelophylax lessonae, Pelophylax esculentus, заповедник, на-заповедник, на-, на-национальный парк
In this paper we considered information on the helminth fauna of the European common brown frog (Rana temporaria Linnaeus, 1758) from 10 regions of the Volga basin. This study includes consolidated data of different authors over the last 30 years, supplemented by the results of our own research. There are reliably known finds of 29 species of helminths: Monogenea -1, Trematoda -21, Nematoda -7. Trematodes Gorgodera asiatica Pigulevsky, 1945, Paralepoderma cloacicola (Luhe, 1909, mtc. and nematodes Icosiella neglecta (Diesing, 1851) were observed for the first time in a given host on the territory of Russia and the Volga Basin. Six species of worms make the basis of helminth fauna: nematodes Rhabdias bufonis, Oswaldocruzia filiformis, Neoxysomatium brevicaudatum and Cosmocerca ornata, trematode Haplometra cylindracea and monogenea Polystoma integerrimum. These six species are the most common and widespread parasites of the brown frog. For each species of helminths there is the following information included: taxonomic position, localization, area of detection, biology, definitive hosts, geographic distribution, the degree of host-specificity.
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.
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