Present distribution of the common frog, Rana temporaria and the moor frog, R. arvalis (Amphibia, Anura) in the “old” Moscow

The common frog (Rana temporaria) and the moor frog (R. arvalis) lived in all green areas of Moscow until the end of the 20th century. The reduction in the area of woody vegetation, the destruction of breeding sites and introduction of the invasive fish Perccottus glenii contributed to the extinction of these amphibians in most of the city. The paper provides information on the distribution of brown frogs in Moscow based on the results of monitoring in 2020. R. temporaria was found in 37 localities in the Northwestern (6 points), Northern (3 points), Northeastern (1 point), Eastern (9 points), Southeastern (1 point), Southern (5 points), Southwestern (5 points) and Western (7 points) administrative districts. Eleven finds (29.7%) are located outside of specially protected natural areas. Most of the species’ habitats (30 points, or 81.1%) are isolated from other populations. R. arvalis was found in 14 localities in the Northwestern (3 points), Northern (3 points), Eastern (4 points), Southwestern (1 point) and Western (3 points) administrative districts of Moscow. Of all the finds noted, three ones (21.4%) are located outside of specially protected natural areas. The vast majority of the habitats of the species (10 points, or 71.4%) are isolated.

INSERT HOST IN THE LIFE CYCLE OF ALARIA ALATA (TREMATODA, STRIGEIDIDA) IN THE NATURAL ENVIRONMENT OF THE CENTRAL BLACK-EARTH ZONE

Currently, an increase in cases of infection of wild and domestic carnivores with the trematode Alaria alata (Trematoda, Strigeidida) is currently recorded in the Central Black-Earth Zone. The trematode A. alata has a complex life cycle involving intermediate, insert and reservoir hosts. We obtained new data on the realization of the life cycle of A. alata in the natural environment of the Central Black-Earth Zone. The moor frog (Rana arvalis), green toad (Bufotes viridis) and spade-footed toad (Pelobates fuscus) are recorded as insert hosts. Infection with mesocercarias A. alata of the moor frog is 20% (the prevalence) and 23 specimens (infection intensity). The moor frog is the most numerous species among amphibians and is characterized by high in-touch capabilities with carnivorous mammals. The moor frog is the main insert host in the circulation of A. alata in natural biocenoses. We have identified the localization of the Alaria mesocercarias in the moor frog, namely, the pericardium and subcutaneous tissue of the intermaxillary space. We determined the distribution of mesocercarias in moor frogs of this year's brood: 71% in the head; 25.8% in the hind legs; 22.6% in the trunk; and 3.2% in the front legs. The green toad and spade-footed toad were also classified as insert hosts of A. alata (prevalence of infection was less than 10%; and infection intensity was 4.0 specimens). Mesocercarias were found in frog larvae (24.6%; 2.6 sp.).

An Overview of the Helminths of Moor Frog Rana arvalis Nilsson, 1842 (Amphibia: Anura) in the Volga Basin

This is the first review of the helminth fauna of the moor frog Rana arvalis Nilsson, 1842 from the Volga river basin (Russia). The article summarizes the authors’ and literature data on the helminthic fauna of this species. The method of complete helminthological dissection was used. Thirthy-eight helminth species were recorded from three classes: Cestoda (1), Trematoda (28), and Chromadorea (9). Nine helminth species are new to the moor frog in Russia: trematodes Gorgodera varsoviensis Sinitzin, 1905, Strigea falconis Szidat, 1928, larvae, Neodiplostomum spathoides Dubois, 1937, larvae, Tylodelphys excavata (Rudolphi, 1803), larvae, Pharyngostomum cordatum (Diesing, 1850), larvae, Astiotrema monticelli Stossich, 1904, larvae and Encyclometra colubrimurorum (Rudolphi, 1819), larvae, nematodes Strongyloides spiralis Grabda-Kazubska, 1978 and Icosiella neglecta (Diesing, 1851). The cestode Spirometra erinacei (Rudolphi, 1918), larvae were observed of this amphibian species in the Volga basin for the first time. The nematodes Rhabdias bufonis, Oswaldocruzia filiformis, Cosmocerca ornata and the trematode Haplometra cylindracea form the core of the helminth fauna of the moor frog. Information on species of helminths includes systematic position, localization, areas of detection, type and scheme of life cycle, geographical distribution, and degree of specificity to host amphibians.

Overwintering and cold tolerance in the Moor Frog (Rana arvalis) across its range

Only two species of boreal Holarctic frogs (genus Rana Linnaeus, 1758) can survive freezing and overwinter on land; they are found in the subarctic and cold regions of North America (Wood Frog, Rana sylvatica LeConte, 1825) and Eurasia (Moor Frog, Rana arvalis Nilsson, 1842) and are an example of an unusual adaptive strategy of overwintering. Freeze tolerance (down to –16 °C) of R. sylvatica has been thoroughly studied; however, little is known about cold resistance of R. arvalis in cold regions. We found that R. arvalis from European Russia and from West Siberia tolerate freezing down to –12 or –16 °C, whereas frogs from the Danish population survived freezing only to –4 °C (Y. Voituron et al. 2009b; J. Comp. Physiol. B, 179: 223–230). All of these populations, according to mitochondrial DNA markers, are closely related. We suggest that the observed differences in cold tolerance (–4 °C vs. –12 or –16 °C) could be caused either by adaptations to climatic factors or by differences in experimental protocols. The northeastern boundary of the geographic range of R. arvalis in Yakutia coincides with the transitional area between discontinuous and continuous permafrost; beyond this area, winter soil temperature sharply declines. The lower lethal temperature and overwintering ecology of R. arvalis in Siberia are similar to those of the North American R. sylvatica.

De novo oviduct transcriptome of the moor frog Rana arvalis: a quest for maternal effect candidate genes

Maternal effects can substantially affect ecological and evolutionary processes in natural populations. However, as they often are environmentally induced, establishing their genetic basis is challenging. One important, but largely neglected, source of maternal effects are egg coats (i.e., the maternally derived extracellular matrix that surrounds the embryo). In the moor frog, the gelatinous egg coats (i.e., egg jelly) are produced in the mother’s oviduct and consist primarily of highly glycosylated mucin type O-glycans. These O-glycans affect jelly water balance and, subsequently, contribute to adaptive divergence in embryonic acid tolerance. To identify candidate genes for maternal effects, we conducted RNAseq transcriptomics on oviduct samples from seven R. arvalis females, representing the full range of within and among population variation in embryonic acid stress tolerance across our study populations. De novo sequencing of these oviduct transcriptomes detected 124,071 unigenes and functional annotation analyses identified a total of 57,839 unigenes, of which several identified genes likely code for variation in egg jelly coats. These belonged to two main groups: mucin type core protein genes and five different types of glycosylation genes. We further predict 26,711 gene-linked microsatellite (simple sequence repeats) and 231,274 single nucleotide polymorphisms. Our study provides the first set of genomic resources for R. arvalis, an emerging model system for the study of ecology and evolution in natural populations, and gives insight into the genetic architecture of egg coat mediated maternal effects.