Water vole (Arvicola amphibious) as an object of long-term biomonitoring in a floodplain area (Western Siberia, Russia)

The paper is devoted to the dynamics of the water vole population in the conditions of total deforestation of valley forests and their subsequent restoration. We analyzed the relative population of small mammals in the typical biotopes in the Tom River basin (Western Siberia) on the border of the forest-steppe and taiga zones. From 1978 to 2019, 1,139 water voles Arvicola amphibius (Linnaeus, 1758) (synonym of A. terrestris) were caught with 50-meter trapping grooves; for 788 individuals we assessed the condition of non-metric features (phenes) of the skull. It was found that changes in the population level are non-cyclical, while against the background of a generally low occurrence of the species in the region, the population level increased tenfold in some years. It was shown that such episodic population surges can significantly impact the structure of the community of small mammals. In the valley of the Tom River, the water vole prefers inhabit wet meadows and ecotone areas between the meadow and the dark coniferous taiga forest. During the years of population surges, the water vole intensely occupies new nesting sites due to the dispersal activity of young animals but at the same time retains the original biotopic preferences. Dispersal of the species takes place in waterlogged wetlands. Most of the animals caught during the peak of their numbers were young animals of late broods born from overwintered individuals. The conducted phenetic analysis revealed the heterogeneity of young animals during the population surge, which allowed us to assume the participation of several populations in the formation of the peak. In the final surge year, the surge was characterized by an extremely low percentage of participation in the breeding of young females and the appearance of a large number of weakened animals, which led to crisis in the species population and the disappearance of the water vole from the captures. The research shows that one cannot predict the success of this process at the current stage; therefore, after flooding, it is necessary to continue monitoring.

Population dynamics of an island population of water voles Arvicola amphibius (Linnaeus, 1758) with one major predator, the eagle owl Bubo bubo (Linnaeus, 1758), in northern Norway

Predator–prey relationships are of great significance to ecosystems, and their effects on the population dynamics of voles and lemmings (Microtinae) in Boreal and Arctic environments have long been of particular interest. A simple ecosystem with one major prey and one major predator could be an ideal setting for a study of their interactions. This is the situation on several small islands on the coast of northern Norway just below the Arctic Circle, with populations of water voles Arvicola amphibius preyed upon by the eagle owl Bubo bubo. The population dynamics of the water vole was studied by trapping and tagging in 2003–2018, eagle owl pellets were collected for analyses, eagle owl breeding attempts were recorded, and some weather variables collected from official recordings. After having been introduced well into the study period, the number of sheep Ovis aries was also recorded. Water voles were the main prey of the eagle owl, with 89% occurrence in pellets, with an overrepresentation of adults and males. Both predation, sheep grazing and extreme weather events influenced the vole population. Predator exclusion, as happened in three summers due to an intensive radio tracking study, especially increased the number of surviving young (in particular from the early cohorts) and the mass of adults. Extreme weather events, such as flooding in summer and deeply frozen ground in winter, most significantly reduced vole populations. Sheep grazing may exacerbate the effects of predation. A similar multitude of factors may affect populations of other rodent species as well.

Helminths in Myomorph Rodents (Rodentia, Myomorpha) from the National Park “Smolny” and Its Surroundings (European Russia)

The National Park “Smolny” is a large forest area, located in the center of European Russia. The helminth fauna of myomorph rodents was studied for the first time within the National Park in 2018–2020. Rodents were examined by the method of complete helminthological dissection. A total of 30 species of parasites were recorded in 11 rodent species: 6 trematodes, 11 cestodes and 13 nematodes. The trematode Plagiorchis maculosus (Rudolphi, 1802) was found in Clethrionomys glareolus (Schreber, 1780) from the Russian fauna for the first time. Clethrionomys glareolus and Microtus arvalis (Pallas, 1779) are new hosts for P. maculosus and metacestode Versteria mustelae (Gmelin, 1790), respectively. The most widespread and eurybiont rodent species have the most diverse and rich helminth fauna, such as C/glareolus (14 species), Apodemus agrarius (Pallas, 1771) (12) and Sylvaemus uralensis (Pallas, 1811) (10). The helminth fauna is less diverse in Sylvaemus flavicollis (Melchior, 1834), M. arvalis (7 species each), Microtus agrestis (Linnaeus, 1761) (5), Microtus subterraneus (de Selys-Longchamps, 1836) (3), Sicista betulina (Pallas, 1779) (2) and Arvicola amphibius (Linnaeus, 1758) (1). Сomparative analysis the helminth fauna of small rodents from the National Park “Smolny” with micromammals from other regions of European Russia revealed that the high similarity with other areas reaches the helminth fauna of M. subterraneus, S. flavicollis, S. uralensis, S. betulina, A. amphibius and M. agrestis.

Photoperiod is involved in the regulation of seasonal breeding in male water voles (Arvicola terrestris)

Mammals living at temperate latitudes typically display annual cyclicity in their reproductive activity: births are synchronized when environmental conditions are most favorable. In a majority of these species, daylength is the main proximate factor used to anticipate seasonal changes and to adapt physiology. The brain integrates this photoperiodic signal through key hypothalamic structures, which regulate the reproductive axis. In this context, our study aims to characterize regulations that occur along the hypothalamo-pituitary-gonadal (HPG) axis in male fossorial water voles (Arvicola terrestris, also known as Arvicola amphibius) throughout the year and to further probe the implication of photoperiod in these seasonal regulations. Our monthly field monitoring shows dramatic seasonal changes in the morphology and activity of reproductive organs, as well as in the androgen-dependent lateral scent glands. Moreover, our data uncover seasonal variations at the hypothalamic level. During the breeding season, Kisspeptin expression in the arcuate nucleus (ARC) decreases, while RFRP3 expression in the dorsomedial hypothalamic nucleus (DMH) increases. Our follow-up laboratory study reveals activation of the reproductive axis and confirms a decrease in Kisspeptin expression in males exposed to a long photoperiod (summer condition) compared to those maintained under a short photoperiod (winter condition) that retain all features reminiscent of sexual inhibition. Altogether, our study characterizes neuroendocrine and anatomical markers of seasonal reproductive rhythmicity in male water voles and further suggests that these seasonal changes are chiefly driven by photoperiod.

Nomen “shchur” as the Ukrainian name of mammals from the genus Arvicola: historical and etymological survey

The ancient Ukrainian zoonym “shchur”, which has long been used for various animals, but most often for large burrowing rodents represented in the aboriginal fauna of Ukraine by the genus Arvicola, is considered. At the same time, this name is also used as a synonym for the word “krysa” (= rat), and in this sense is often identified with the genus Rattus (“patsiuk” = rat) to denote various large rodents from distant lands following a principle “ the small = mice, the large = rats”. Therefore, the name “shchur” is often considered ambiguous and thus worth either forgetting or using only for the alien species. Etymological hypotheses are considered, of which the most relevant to zoological specifics is the one that explains the connection with burrows, ground, and night. This set of features determines the general ecomorphological type: large long-tailed underground mouse-like rodents with expressed nocturnal activity, which appearance in human economies is undesirable. The history of use of the name “shchur” in the special literature, mainly in zoological reviews and other zoological studies, in the period from 1874 to 2020 is analysed. The widespread use of the nomen to denote different groups of animals, and especially rodents of the ecomorphological type “large mice”, which are representatives of the genera Arvicola and Rattus, is shown. Analysis of old sources showed that the name “shchur” was originally used as a common “generic” name for all species as well as some intraspecific forms of both genera, with the definition of semantic differences in the species modifier: water, common, ground, nomadic, basement, black, ship, mill, and so on “shchur”. Unambiguous fixation of Ukrai­nian generic names as equivalents to scientific generic names required the typification of all names, which took place in the Ukrainian scientific nomenclature in the late XIX and early XX centuries. As a result, the name “rat” is proposed to be assigned to the genus Arvicola, and for the genus Rattus to be recorded as the Ukrainian equivalent of the nomen “patsiuk” (“rat”). Arguments are presented to recognise the antiquity of the zoonym “shchur” and therefore to recognise its importance for the designation of aboriginal rodent species, and especially of “water shchur” (water vole, Arvicola amphibius) voles of the genus Arvicola in general. The practice of traditional naming of laboratory rats as “shchur”, as well as the use of the name “shchur” with appropriate definitions to refer to other genera, inclu­ding muskrats (“musk shchur” or “musk rat”), nutria (“marsh shchur” or “marsh rat”) and various representatives of distant faunas (bamboo or spiny tree-rats, etc.) in the Ukrainian zoonymics should be abolished.

The genome sequence of the European water vole, Arvicola amphibius Linnaeus 1758

We present a genome assembly from an individual male Arvicola amphibius (the European water vole; Chordata; Mammalia; Rodentia; Cricetidae). The genome sequence is 2.30 gigabases in span. The majority of the assembly is scaffolded into 18 chromosomal pseudomolecules, including the X sex chromosome. Gene annotation of this assembly on Ensembl has identified 21,394 protein coding genes.