Oswaldocruzia ukrainae (Nematoda: Molineidae)-A Parasite of European Green Toad Bufotes viridis: Morphological and Molecular Data.

Nematodes of the genus Oswaldocruzia are common parasites of the small intestine of amphibians and reptiles. Our recent molecular analysis of Oswaldocruzia nematodes revealed that only Oswaldocruzia filiformis, which possesses high morphological variability, parasitizes amphibians and reptiles in European Russia. Here we present the study of Oswaldocruzia nematodes from the European green toad Bufotes viridis (Anura, Bufonidae) collected at different localities of the Middle Volga region in 2018-2022. We analyzed the morphological characteristics of the Oswaldocruzia spp. taxonomy together with novel molecular phylogenetic data. The data on phylogenetic analysis (based on partial CoxI mtDNA gene sequences) showed that Bufotes viridis is parasitized by two Oswaldocruzia species, the host-specific parasite Oswaldocruzia ukrainae and species generalist Oswaldocruzia filiformis. Broad morphological variability was revealed in O. ukrainae nematodes both from the same host specimen and from various toad individuals from different localities. Our results highlight the need for further biodiversity research of morphologically similar Oswaldocruzia species from amphibians and reptiles in the Western Palearctic using molecular genetic methods.

Diversity of trematodes from the amphibian anomaly P hotspot: Role of planorbid snails.

Trematode infection of the second intermediate hosts can lead to changes in their fitness and, as a result, a change in the invasion rate of animal communities. It is especially pronounced during the invasion of parasite species that reduce activity due to the manipulation of hosts through the changes of their morphology and physiology. One of these cases is an anomaly P syndrome hotspot found in some populations of water frogs and toads in Europe caused by the trematode Strigea robusta metacercariae. The occurrence of pathogen and their participation in ecosystems are intrigues questions in the anomaly P phenomenon, as well as the role of planorbid snails that serve as the first intermediate hosts for many trematode species. Herein, we focused on trematodes spectra from planorbid snails and amphibians from the anomaly P hosts with the aim to undetected interactions between the pathways of parasites. Emerging cercariae of 6802 planorbid snails of dominant species (Planorbarius corneus, Planorbis planorbis, and Anisus spp.) were detected by both morphological and molecular methods in seven waterbodies in Privolzhskaya Lesostep Nature Reserve (Russia). A total of 95 sequences of 18 species were received, and 48 sequences were unique and did not present in any genetic databases. The 18 species of trematodes from snails and 14 species of trematodes from amphibian hosts (Pelophylax ridibundus; Ranidae; Anura) were detected. Three species (Echinostoma nasincovae, Tylodelphys circibuteonis and Australapatemon burti) was new for the trematode fauna of the Middle Volga River region and Russia as a whole. Eleven species of parasitic flatworms have amphibians in their life cycles and nine species used amphibians as metacercariae hosts: Echinostoma nasincovae, E. miyagawai, Echinoparyphium recurvatum, Tylodelphys circibuteonis, Neodiplostomum spathula, Paralepoderma cloacicola, Macrodera longicollis, Strigea robusta, and Strigea strigis. The occurrence of trematode species from planorbid mollusks and frogs were compared.

Parásitos nematodos de la rana de piscina (Pelophylax lessonae) en la cuenca del Río Volga / Parasitic nematodes of Pool Frog (Pelophylax lessonae) in the Volga Basin

RESUMEN Objetivo. Presentar una revisión moderna de la fauna de nematodos de la rana esculenta Pelophylax lessonae (Camerano, 1882) de las poblaciones de la cuenca del Río Volga. Materiales y métodos. Este trabajo consolida los datos de diferentes trabajos helmintológicos de los últimos 80 años, respaldados por los resultados de nuestras propias investigaciones. Durante el período de 1936 a 2016 diferentes autores examinaron 1460 especímenes de rana esculenta, utilizando el método de autopsia helmintológica completa de 13 regiones de la cuenca del Río Volga. Resultados. En total se registraron 9 especies de nematodos. Nematodo Icosiella neglecta encontrado por primera vez en el huésped estudiado en el territorio de Rusia y la cuenca del Río Volga. Tres especies parecían estar más extendidas: Oswaldocruzia filiformis, Cosmocerca ornata e Icosiella neglecta. Para cada especie de helmintos se incluyó la siguiente información: posición sistemática, áreas de detección, localización, biología, lista de hospederos definitivos, nivel de especificidad del hospedero. Conclusiones. Los nematodos de la rana esculenta, excepto I. neglecta, pertenecen al grupo de helmintos transmitidos por el suelo (geohelmintos) y parasitan en estadios adultos. Algunas especies (O. filiformis, C. ornata, I. neglecta) están muy extendidas en el área de distribución del hospedador. Estos dos últimos son capaces de alcanzar altos índices de invasión y también de ser los parásitos subyacentes de la rana esculenta. Esto sucede debido a la especificidad del ciclo de vida de estas especies de nematodos y a la conexión a largo plazo del anfibio con el agua.

ABSTRACT Objetive. Present a modern review of the nematodes fauna of the pool frog Pelophylax lessonae (Camerano, 1882) from Volga basin populations on the basis of our own research and literature sources analysis. Materials and methods. Present work consolidates data from different helminthological works over the past 80 years, supported by our own research results. During the period from 1936 to 2016 different authors examined 1460 specimens of pool frog, using the method of full helminthological autopsy, from 13 regions of the Volga basin. Results. In total 9 nematodes species were recorded. Nematode Icosiella neglecta found for the first time in the studied host from the territory of Russia and Volga basin. Three species appeared to be more widespread: Oswaldocruzia filiformis, Cosmocerca ornata and Icosiella neglecta. For each helminth species the following information included: systematic position, areas of detection, localization, biology, list of definitive hosts, the level of host-specificity. Conclusions. Nematodes of pool frog, excluding I. neglecta, belong to the group of soil-transmitted helminthes (geohelminth) and parasitize in adult stages. Some species (O. filiformis, C. ornata, I. neglecta) are widespread in the host range. The latter two are able to reach high invasion indices and also to be the background parasites of the pool frog. It happens due to these nematode species life cycle specificity and the long-term connection of the amphibian with water.