Microtus Oeconomus Research Articles

Los micromamíferos (Eulipotyphla, Chiroptera, Rodentia y Lagomorpha) del yacimiento del Pleistoceno Superior de la cueva de El Castillo (Cantabria, España)

El material de micromamíferos del yacimiento del Pleistoceno Superior de la cueva de El Castillo, objeto de estudio detallado en este trabajo, proviene de los niveles auriñacienses 18b y 18c (datados en 40.000-45.000 BP), nivel 19, y niveles musterienses 20b, 20c, 20d, 20e (datados en 41.000-49.000 BP), 21a y 21b. La asociación de micromamíferos es la siguiente: Erinaceus europaeus, Crocidura russula, Sorex coronatus, Sorex minutus, Neomys fodiens, Talpa europaea, Galemys pyrenaicus, cf. Miniopterus schreibersii, Chiroptera indet., Pliomys lenki, Microtus arvalis – Microtus agrestis, Microtus lusitanicus, Microtus oeconomus, Chionomys nivalis, Arvicola terrestris, Apodemus sylvaticus – Apodemus flavicollis y Lepus sp. La mayoría de estas especies están presentes en la fauna actual de Cantabria, excepto Pliomys lenki que se extinguió en el último tercio del Pleistoceno Superior, y Microtus oeconomus, que persistió en la península ibérica durante el Holoceno bien avanzado hasta su desaparición en tiempos históricos, y que actualmente está en regiones euroasiáticas más septentrionales. Hay una gran continuidad de la gran mayoría de los taxones en todos los niveles. La fauna en su conjunto parece indicar un medio predominantemente abierto, por lo general de praderas húmedas (y en mucha menor medida praderas secas) con una buena cobertura vegetal a nivel del suelo, en el que habría también algunas zonas arboladas o boscosas, y algún curso de agua. Los indicadores termófilos son escasos y poco abundantes, lo que podría indicar que el clima podría ser algo menos templado que en otros periodos del Pleistoceno Superior y quizás también que actualmente en la zona.

Experience of applying plant and animal fluctuating asymmetry in assessment of environmental quality in terrestrial ecosystems: Results of 20-year studies of wildlife and anthropogenically transformed territories

The value of fluctuating asymmetry (FA) of trees and small mammals is considered as an indicator of developmental instability. The urban territories with recreation zones, sites with increased radiation background, and the areas affected by mining facilities have been analyzed as anthropogenically transformed areas. The following tree and small mammalian species are the objects of the study: Siberian silver birch (Betula platyphylla), spreading birch (B. divaricata), dwarf birch (B. exilis), shrub alder (Duschekia fruticosa), basket willow (Salix viminalis), northern red-backed vole (Clethrionomys rutilus), tundra vole (Microtus oeconomus), Laxmann’s shrew (Sorex caecutiens), and tundra shrew (S. tundrensis). In total, 60000 leaves have been measured and 3500 rodent sculls have been examined. The issues of selection of bioindicator species and the factors distorting the results of environmental quality assessment according to developmental instability are discussed. A statistically significant increase in FA of plants is recorded in urban territories as compared with the wildlife biotopes. A positive correlation of FA value with transport load, concentration of heavy metals in soil, and atmospheric air pollution is observed. The proximity to a roadway and the state of road pavement influence the FA value. The main source of pollution in the administrative center (Yakutsk) is motor vehicles; correspondingly, large streets and crossroads with a high transport load are the most polluted sites. As for the industrial center (city of Mirnyi), pollution spreads from the areas affected by mining to the residential area. The main pollution source in a small administrative center (city of Aldan) is the federal highway. It is recommended to concurrently use the FA characteristics of plant and animals in the area affected by the mining industry. Characteristic of this industry is withdrawal of large areas of natural landscapes; typically, transformed plots alternate weakly affected plots. The specific features of the effects of diamond, gold, and coalmining industries, as well as oil and gas field development, are discussed, which should be taken into account in sampling for bioindication. The problem of bioindication in the areas completely devoid of soil and plant cover can be solved by biotesting via assessment of bunching onion seed germination rate and the rate of mitotic aberrations. An increase in the FA level in trees and small mammals is observed in the areas transformed by the mining industry displaying a chronically increased radiation background and oil-polluted as a result of technogenic accidents. The use of FA index makes it possible to estimate the environmental quality and to compare the state of territories located under different natural and climatic conditions and influenced by multicomponent anthropogenic impacts differing in their strength and genesis, which interferes with their comparison.

Niche Dynamics and Biodiversity: Many Rodent Species on One Marshy Meadow

The ecological niche of a species is determined by its tolerance to environmental factors and by interactions with other species, particularly those using the same resource. We assessed spatial niches of four rodent species coexisting in one meadow habitat within the Bialowieza Primeval Forest. Niche characteristics were based on the valorisation of the habitat around live-trapping sites visited by rodents during seven years of the study. The population size of each species was monitored and expressed as an average annual density. The root vole Microtus oeconomus was the most numerous and dominant species, with its density widely fluctuating due to the temporal increases of predation pressure exerted by the weasel Mustela nivalis. During the study period, the spatial niche of the root vole was nearly constant, with only significantly increased tolerance towards shrub covered sites at times of its high population density. However, even a slight niche expansion of the highly abundant root voles displaced accompanying species: the bank vole Myodes (Clethrionomys) glareolus, the yellow necked mouse Apodemus flavicollis and the striped field mouse A. agrarius, from their preferred sites and efficiently decreased rodent species diversity in the studied habitat. This study illustrates a possible mechanism of the direct effect of predation on the dominant prey species population and indirect one on the species diversity changes over ecological time.

Genetic variability of the cold-tolerant Microtus oeconomus subspecies left behind retreating glaciers

The current range of the root vole (Microtus oeconomus) in Europe has been shaped by climate changes, including the last glaciation. In Central Europe there are two isolated subspecies: M. oeconomus mehelyi and M. oeconomus arenicola occurring in the Pannonian lowland and the Netherlands respectively. M. oeconomus stimmingi is present in the northern part of Central Europe in the continuous range of the species distribution. To establish the influence of the postglacial isolation on the subspecies performance, we sampled 192 individuals at seven sites from the three geographic regions. Individuals were genotyped at 14 microsatellite loci highly polymorphic for all subspecies studied. This is the first extensive research presenting the diversity of M. oeconomus mehelyi from Central Europe at the molecular level. Its genetic diversity (Ar=6.6, SD=0.4) as well as effective population size (LDNe=170, SD=62) were significantly lower than in the other two subspecies, their average Ar=7.6, SD=0.2 and LDNe=504, SD=134, suggesting M. oeconomus mehelyi is most threatened with extinction. None of the subspecies showed significant genetic bottleneck signatures. The differential analysis of the genetic structure of various subgroups resulting from clustering analysis was performed to reveal the genetic relationships among individuals within and between geographic regions. We found a closer relation of M. oeconomus stimmingi with each of the isolated subspecies than between them. Moreover, we detected a clear substructure in Pannonian M. oeconomus (two subgroups), that could result from more than one colonization episode.

Laelapidae mites (Acari: Mesostigmata) infesting small rodents in the Curonian Spit, Lithuania

Laelapidae (Acari, Mesostigmata) mites are ecologically diverse and involve predators and parasites found in various habitats. In the present study, Laelapidae mites were collected from 236 small rodents of five species (the yellow-necked mouse Apodemus flavicollis, the harvest mouse Micromys minutus, the bank vole Myodes glareolus, the root vole Microtus oeconomus, and the field vole Microtus agrestis) in the Curonian Spit in 2013–2014. Five species of Laelapidae mites – Laelaps agilis, Hyperlaelaps microti, Haemogamassus nidi, Eulaelaps stabularis and Myonyssus gigas – were identified based on the morphological characters of adult females and males. The present study is the first detection of Laelapidae mites parasitizing small rodents in the Curonian Spit, Lithuania.

Concentration and size distribution of plant fiber in the digestive tract of muroid rodents

The weight parameters that characterize the size and the degree of fullness of fermentation chambers (forestomach and cecum), namely, the weight of the walls and the content of these organs, and the concentration and size distribution of fibers in the chyme have been investigated in five muroid rodent species (Arvicola terrestris, Microtus oeconomus, Microtus arvalis sp., Clethrionomys glareolus, and Sylvaemus flavicollis). No distinct regularities were observed in the above-mentioned parameters of the forestomach. These parameters of the cecum were generally found to be in good agreement with the conventional concept of dietary specialization of the rodent species under investigation, but the results have provided a more precise assessment of the role of dietary fiber in the diet of free-living rodents under specific environmental conditions.

The role of interspecies differences in the ratio of choline-containing phospholipid fractions of rodent erythrocytes in response of these cells to the effect of membranotropic compounds

In in vitro experiments, interspecies differences were revealed in the erythrocyte responses in varied rodent species—laboratory mice (Mus musculus L.), tundra voles (Microtus oeconomus Pall.) and bank voles (Myodes glareolus Pall.)—to the effect of chemical agents able to interact with membrane lipids and disrupt the membrane structure (detergent Triton X-100, oxidative stress inductor AAPH, antioxidant ionol or BHT, uranyl ion). It was hypothesized that these differences are due to physicochemical peculiarities of the erythrocyte membrane structure, specifically, the ratio of choline-containing fractions of phospholipids (phosphatidylcholine and sphingomyelin). The use of blood erythrocytes as an in vitro experimental model to study the mechanisms of toxicity as well as antioxidant and membrane-protective properties of compounds of different nature was shown to imply the choice of an adequate source of erythrocytes in view of considerable speciesdependent structural specificity of the lipid component of mammalian erythrocyte membranes.

The nexus of hair corticosterone level, immunocompetence, metabolic rates and overwinter survival in the root vole, Microtus oeconomus

Although corticosterone (CORT) regulates many physiological mechanisms, the associations between CORT levels, immunocompetence, energy expenditures and overwinter survival have not been examined. Here, we studied individual variation in CORT level extracted from hair, immunocompetence quantified as the neutrophil-to-lymphocyte (N/L) ratio, total white blood cells (WBC) and natural antibody levels (NAbs), along with the resting (RMR) and peak metabolic rates (PMR) and mortality during three consecutive winter seasons in a natural population of the root vole, Microtus oeconomus. In early winter, hair CORT level was strongly positively associated with body mass and inversely related to voles’ ability to survive. We suggest that the observed association between hair CORT level and body mass may be the key component of the physiological nexus driving the survivorship of individual rodents. Additionally, hair CORT was a significant predictor of variation of the whole body RMR, which in turn enhanced overwinter survival in the studied population. On the other hand, hair CORT was not significantly associated with changes in the blood indices. Interestingly, the analysis carried out only during the first year of study (2008), which was characterized by a high population density and prevalence of infestation with a blood protozoan, Babesia spp., showed that the intensity of the infestation was negatively correlated with both the hair CORT level and the N/L ratio. Because CORT is often considered immunosuppressive, we expected a positive association between its level and the N/L ratio. However, hair CORT did not significantly correlate with the N/L ratio. We suggest that the lack of an association between hair CORT and the N/L ratio resulted from a small inter-individual variation in the N/L ratio in 2008, which was much higher and less variable than in the other years of our study.

Barn Owl (Tyto alba) Diet Composition on Intensively Used Agricultural Land in the Danube Lowland

Based on pellets analysis from five localities in south western Slovakia (Malá Mužla, Malé Ripňany, Obid, Opatovský Sokolec and Tešedíkovo), we studied the diet composition of Barn Owl (Tyto alba) in intensively cultivated agricultural lands. A total of 6218 specimens of prey, 17 mammalian and 7 bird species were identified. The main prey species found in all food samples was the Common Vole (Microtus arvalis), varying between 56 % and 67 %. The proportion of synanthropic species (Rattus norvegicus, Passer domesticus) and species inhabiting agricultural landscapes (Crocidura leucodon, Crocidura suaveolens, Mus sp.) increases in localities with a lower ratio of the Common Vole. The results suggest land use affects the diet of Barn Owls, confirming conclusions which have been drawn in previous studies. From faunistic point of view, discovering the Pannonian Root Vole (Microtus oeconomus mehelyi) in the diet from Malá Mužla was important.

Prevalence, genetic identity and vertical transmission of Babesia microti in three naturally infected species of vole, Microtus spp. (Cricetidae)

BackgroundVertical transmission is one of the transmission routes for Babesia microti, the causative agent of the zoonotic disease, babesiosis. Congenital Babesia invasions have been recorded in laboratory mice, dogs and humans. The aim of our study was to determine if vertical transmission of B. microti occurs in naturally-infected reservoir hosts of the genus Microtus.MethodsWe sampled 124 common voles, Microtus arvalis; 76 root voles, M. oeconomus and 17 field voles, M. agrestis. In total, 113 embryos were isolated from 20 pregnant females. Another 11 pregnant females were kept in the animal house at the field station in Urwitałt until they had given birth and weaned their pups (n = 62). Blood smears and/or PCR targeting the 550 bp 18S rRNA gene fragment were used for the detection of B. microti. Selected PCR products, including isolates from females/dams and their embryos/pups, were sequenced.ResultsPositive PCR reactions were obtained for 41% (89/217) of the wild-caught voles. The highest prevalence of B. microti was recorded in M. arvalis (56/124; 45.2%), then in M. oeconomus (30/76; 39.5%) and the lowest in M. agrestis (3/17; 17.7%). Babesia microti DNA was detected in 61.4% (27/44) of pregnant females. Vertical transmission was confirmed in 81% (61/75) of the embryos recovered from Babesia-positive wild-caught pregnant females. The DNA of B. microti was detected in the hearts, lungs and livers of embryos from 98% of M. arvalis, 46% of M. oeconomus and 0% of M. agrestis embryos from Babesia-positive females. Of the pups born in captivity, 90% were born to Babesia-positive dams. Babesia microti DNA was detected in 70% (35/50) of M. arvalis and 83% (5/6) of M. oeconomus pups. Congenitally acquired infections had no impact on the survival of pups over a 3-week period post partum. Among 97 B. microti sequences, two genotypes were found. The IRU1 genotype (Jena-like) was dominant in wild-caught voles (49/53; 92%), pregnant females (9/11; 82%) and dams (3/5; 60%). The IRU2 genotype (Munich-like) was dominant among B. microti positive embryos (20/27; 74%) and pups (12/17; 71%).ConclusionA high rate of vertical transmission of the two main rodent genotypes of B. microti was confirmed in two species of naturally infected voles, M. arvalis and M. oeconomus.

Variants of tooth mesowear in Microtus voles as indicators of food hardness and abrasiveness

Methodological approaches to the description of variants and degrees of hypselodont tooth mesowear in voles are proposed on the basis of studies on the collection of skulls of two vole species trapped in the field (narrow-headed vole, n = 38; common vole, n = 22) and two species from laboratory colonies (narrow-headed vole, n = 46; root vole, n = 76). Trends in the manifestation of different mesowear variants have been analyzed in experiments on feeding root voles from the laboratory colony with “hard” and “soft” foods. It has been found that animals kept on low-abrasive diet show signs of wear due to tooth-to-tooth contact, such as low crown height, relatively obtuse wear angle and more upright position of m/1 in the jaw, shallow occlusal surface relief, and lateral wear facets. Chewing hard food items requires application of vertical occlusal pressure, which result in the formation of a depression in repair dentin, while denser dentin at the anterior enamel wall of prisms remains unworn.

Heterogeneity of 90Sr radioactive contamination at the head part of the East Ural radioactive trace (EURT)

1We measured 90Sr concentrations and beta particle flux density (BPFD) in 44 soil samples collected from four soil profiles across a central transect on the head of the East Ural Radioactive Trace (EURT). The relationship between BPFD and 90Sr concentration of each soil sample can be characterised by a linear regression model; 90Sr concentration in the upper 12 cm soil layer can thus be assessed by measuring BPFD in the soil surface. 2The BPFD on the soil surface was measured at 969 points at seven sites with linear dimensions ranging from 140 × 20 m to 140 × 320 m. The correspondence of 90Sr concentration in the 12 cm soil layer with its BPFD value was calculated for each of these seven sites. Eighty (80) % of 90Sr concentration measurements in the 12 cm soil layer in each model site differed by a factor of 2.0–5. The variability of 90Sr concentration increased significantly in the 12 cm upper soil layer over territories with visual features of landscape disturbance (pits, trenches). The ratio of maximum to minimum concentration of 90Sr varied from 6.1 to 6.6 in the 12 cm soil layer over territories without visual features of anthropogenic soil disturbance. 3The 90Sr concentration was measured in the skeletons of 34 juvenile Microtus oeconomus individuals weighing less than 12.5 g and trapped at the four model sites in July. The assessment of 90Sr concentration in the 12 cm soil layer was conducted for each point where an animal was trapped. The relationship between 90Sr concentration in soil and in the skeleton was characterised by a linear regression model with a determination coefficient of 0.51. 4The concentration ratio for 90Sr from soil to skeleton (CRskeleton-soil) was 2.0 ± 0.1 for M. oeconomus over the territory of the EURT, which is consistent with the minimum value of the same CRskeleton-soil for M. oeconomus from the Chernobyl area (Chesser et al., 2000).

Metagenomic Evaluation of Bacteria from Voles.

Voles (Arvicolinae, Rodentia) are known carriers of zoonotic bacteria such as Bartonella spp. and Francisella tularensis. However, apart from F. tularensis, the bacterial microbiome of voles has not previously been determined in Finland and rarely elsewhere. Therefore, we studied liver samples from 61 voles using 16S ribosomal RNA gene PCR analysis, followed by Sanger sequencing. Twenty-three of these samples were also studied with tag-encoded pyrosequencing. The samples originated from 21 field voles (Microtus agrestis), 37 tundra voles (Microtus oeconomus), and 3 bank voles (Myodes glareolus). With the more conventional 16S rDNA PCR analysis, 90 (33%) of the recovered 269 sequence types could be identified to genus level, including Bartonella, Francisella, Mycoplasma, Anaplasma, and Acinetobacter in 31, 15, 9, 9, and 9 sequences, respectively. Seventy-five (28%) matched best with sequences of uncultured bacteria, of which 40/75 could be classified to the order Clostridiales and, more specifically, to families Lachnospiraceae and Ruminococcaceae. Pyrosequencing from 23 samples revealed comparable and similar results: clinically relevant bacterial families such as Mycoplasmataceae, Bartonellaceae, Anaplasmataceae, and Francisellaceae were recognized. These analyses revealed significant bacterial diversity in vole livers, consisting of distinct and constant sequence patterns reflecting bacteria found in the intestinal gut, but including some known zoonotic pathogens as well. The molecular bacterial sequence types determined with the two different techniques shared major similarities and verified remarkable congruency between the methods.

Taxonomic position of Chinese voles of the tribe Arvicolini and the description of 2 new species from Xizang, China.

China has 26 species in the tribe Arvicolini. The taxonomic status of these voles remains controversial despite much effort. Herein, we evaluate the taxonomic position of 22 species plus 2 unidentified taxa using mitochondrial DNA gene sequences (cytb + CO1). We also evaluate 18 species and 2 unidentified taxa using morphological data. Phylogenetic analyses of cytb resolve monophyly for the genera Alexandromys, Lasiopodomys, Microtus, Neodon, Proedromys, and Volemys with strong support. Stenocranius clusters with Chionomys but with very weak support. Analyses of concatenated cytb + CO1 resolve the same genera with strong support, but the topology of the tree differs from that of cytb in that Chionomys roots at the base of the tree independent of Stenocranius, which forms the sister-group of Lasiopodomys in a more terminal position. The matrilineal genealogy excludes the type species Arvicola amphibius from the rest of the Arvicolini. This species forms the sister-group of Ondatra with high support. Neodon includes N. irene, N. linzhiensis, N. fuscus, N. leucurus, N. sikimensis, Microtus clarkei, and 2 unidentified specimens. Alexandromys includes the former species Microtus oeconomus, M. kikuchii, M. limnophilus, M. fortis, and M. maximowiczii. Finally, Microtus has the subgenera Blanfordimys, Microtus, Mynomes, Pedomys, Pitymys, and Terricola, which includes the Chinese species M. agrestis, M. arvalis, and Blanfordimys juldaschi. General mixed Yule-coalescent species delimitation modeling demarcates 6 currently recognized species and 2 new species of Neodon. A principal component analysis of the morphological data among 7 matrilines shows that all variables have positive loadings of high magnitude on the 1st component. Canonical discriminant analysis for Neodon (including M. clarkei and 2 unidentified species) correctly classifies 93.0% of specimens. Overall, our analyses support the recognition of Alexandromys, Lasiopodomys, Microtus, Neodon, Proedromys, and Volemys as genera. Stenocranius includes Microtus gregalis, and the genealogical position of Stenocranius remains uncertain. The status of Arvicola requires further study. We assign M. clarkei to Neodon and describe 2 new species of Neodon.

Last Neanderthals and first Anatomically Modern Humans in the NW Iberian Peninsula: Climatic and environmental conditions inferred from the Cova Eirós small-vertebrate assemblage during MIS 3

Cova Eirós is emerging as a reference site in the northwestern Iberian Peninsula for the study of the development of the last Neanderthal populations and the first populations of Anatomically Modern Humans (AMH) in MIS 3. Cova Eirós is an archaeological site (with Middle and Upper Palaeolithic levels) located in Cancelo, Triacastela (Lugo, northwestern Iberian Peninsula), which has been systematically excavated from 2008 onwards. The small-vertebrate assemblage analysed came from the archaeo-palaeontological field seasons that took place from 2009 to 2014. At least 18 small-vertebrate taxa have been identified: 1 frog (Rana temporaria), 1 snake (Vipera sp.), 4 insectivores (Sorex minutus, Sorex sp., Talpa cf. occidentalis and Erinaceus europaeus), 4 chiropters (Myotis myotis/blythii, cf. Miniopterus sp., Myotis sp. and Rhinolophus ferrumequinum) and 8 rodents (Apodemus sylvaticus, Arvicola amphibius, Arvicola sapidus, Chionomys nivalis, Microtus (Terricola) lusitanicus, Microtus agrestis, Microtus arvalis and Microtus oeconomus). Using the Habitat Weighting method to reconstruct the palaeoenvironment, we reconstruct a landscape for MIS 3 characterized by open woodland formations. The Mutual Ecogeographic Range (MER) method and the Bioclimatic Model (BM) used for the palaeoclimatic reconstruction show lower temperatures and higher precipitation than at present in the region. Our results from Cova Eirós are compared with the data obtained from several other sites in the Iberian Peninsula; it can be said that Neanderthals and AMH were well adapted to the territory that they occupied, as well as to the surrounding environment and the climatic conditions prevalent in the unstable context of MIS 3 in the Iberian Peninsula.

Fauna of gamasina mites (Gamasoidea) of small mammals of a natural region «Samarskaya Luka»

Data on fauna of gamasina mites parasitizing on small mammals are provided in article. Data are obtained during long-term monitoring of an ecological complex of small mammals of a natural and territorial complex Samarskaya Luka, which is realized since 1999. Also data on fauna of gamasina mites in 14 years of researches (20002003, 2005, 20072015 years), including literary data about the gamasina mites of this territory, are generalized and analysed. Specific accessory of 7439 individuals of mites, seven childbirth of three families relating to fifteen types is defined. Parasitizing the gamasina mites on 16 species of small mammals, including groups rodents, soricomorpha, carnivora (least weasel) is established. Domination of separate species of mites is revealed, so to eudominant Laelaps hilaris and Hirstionyssus isabellinus are belong, dominants are Hirstionyssus ellobii, Haemolaelaps glasgowi, Hyperlaelaps arvalis, L. agilis. Myonyssus rossicus, L. algericus, Haemogamasus ambulans and Hirstionyssus macedonicus were extremely rare species met in single copies. For the first time for this territory types of H. ellobii, L. micromydis, H. ambulans, H. macedonicus are noted. Conclusions on degree of a confinedness of parasites to certain types of hosts are drawn. Monohostal types: L. agilis (the host a yellow-necked mouse), L. muris (the host a tundra vole and a water vole), L. micromydis (the host a small mouse), L. algericus (the host a house mouse), H. arvalis (the host a tundra vole and a water vole), H. ellobii (the host a northern mole vole). Polihostal: H. musculi, L. hilaris, H. isabellinus, H. glasgowi, E. stabularis, H. nidi.

ИНФИЦИРОВАННОСТЬ БАБЕЗИЯМИ МЕЛКИХ МЛЕКОПИТАЮЩИХ ЮЖНОЙ ТАЙГИ ОМСКОЙ ОБЛАСТИ

Blood samples were taken from 541 small mammal captured in 2013–2015 in Znamensky district of Omsk region from
 Ixodes persulcatus and Ixodes trianguliceps sympatric area and examined for the Babesia spp. presence by nested PCR
 with subsequent sequencing of positive samples. Babesia microti DNA was found in 31,1 % of positive samples; a proportion
 of infected mammals varied from 5,3 % to 61,6 % in different sampling periods. B. microti DNA was found in
 samples from three prevailing Myodes species as well as from a root vole (Microtus oeconomus), field voles (Microtus
 argestis) and Siberian chipmunks (Tamias sibiricus). It was shown that identified B. microti samples belong to two
 genetic groups: B. microti ‘US’-type and B. microti ‘Munich’-type; notably that > 90 % infected mammals contained
 DNA of nonpathogenic for human B. microti ‘Munich’-type. We suppose that I. trianguliceps tick is the most probable
 vector of B. microti ‘Munich’-type.

Denovo lipogenesis is suppressed during fasting but upregulated at population decline in cyclic voles.

Arvicolines are susceptible to the development of fatty liver during short-term fasting. We examined the potential role of de novo lipogenesis (DNL) (i) in the development of fasting-induced fatty liver and (ii) during a population cycle by measuring the mRNA expression of acetyl-CoA carboxylase-1 (ACC1) and fatty acid synthase (FAS). Laboratory voles (Microtus oeconomus and Microtus arvalis) were fed or fasted for 12 or 18 h and their liver mRNA levels were determined. Both species showed decreased mRNA expression of ACC1 and FAS during fasting. This suggests that DNL does not participate in the development of fatty liver in voles, different from human non-alcoholic fatty liver disease. In wild bank voles (Myodes glareolus), the mRNA levels of the genes of interest were higher during the population decline compared to the increase phase. In conclusion, DNL was suppressed during acute fasting but upregulated during a long-term population decline-a period of purported scarcity of high-quality food.

Plant defences wear vole teeth

In the fields of Northern Europe, a tundra vole (Microtus oeconomus) population explosion could be going on right now. As they hit the reproductive jackpot, their numbers rocket. But with most booms there comes a bust, and the same is true for vole populations, which can collapse suddenly and unexpectedly. Ivan Calandra, from the University of Reims Champagne-Ardenne, France, explains that the cause of these dramatic population crashes was not clear, although there was one candidate that could account for the dramatic fall from grace: the vegetation upon which the voles feast. Plants are not as vulnerable as they may at first appear. ‘It has been known for at least 30 years that plants build up silica bodies (phytoliths) in response to intense grazing,’ says Calandra. But it was not clear whether these plant defences were directly responsible for the vole's demise, and if they were, how? Were the abrasive silica structures that accumulate in plant cells wrecking the rodents' teeth or damaging their intestines, leading to starvation and population collapse?Karol Zub, Andrzej Zalewski and Paulina Szafrańska, from the Polish Academy of Sciences, decided to feed voles on two diets – one composed of pellets containing high levels of sedge, which is reinforced with silica, and another in which the sedge was replace with lower-silica grasses – to find out how different levels of silica affected the rodents’ teeth. Then Zub and Szafrańska shipped the voles’ teeth to Gildas Merceron, a CNRS Researcher at the University of Poitiers, France, where he and Calandra could look for any damage using one of only four profilometers – confocal microscopes that scan surfaces to produce 3D representations of structures – that can analyse tooth wear.However, when the duo compared the damage on the surface of teeth that the voles had used to grind their food, they were surprised to see little difference between the patterns of wear in animals on the different diets, possibly because the lab diets were not optimal. However, Calandra's Polish colleagues also knew that voles switch diet from season to season, dining on high-silica sedges in the winter and spring before supplementing the diet with softer, low-silica leafy vegetation in the summer and autumn. In addition, Calandra explains that sedges retaliate as the vole population expands by arming themselves with increased silica levels. Could the team find differences in tooth wear if they investigated the wear patterns in different populations of voles across the years and seasons as the silica levels increased in response to the expanding populations?This time the team investigated vole teeth from animals that had been trapped in the wild from the late 1970s to 2001, including a period when the population crashed in 2000 after peaking the previous year. And this time, having scanned the surface of 47 teeth, they found evidence of changes in wear pattern as the voles shifted their diet through the seasons and as the sedges became more impregnated with silica.However, the team warns that this evidence of changes in tooth wear may not account for vole population crashes, saying, ‘Tooth wear rates might seem unimportant in voles since their molars are ever-growing’. They also add that there is no clear mechanism linking the effects of tooth wear to dramatic reductions in vole population, although they suspect that if the teeth are worn unevenly, the animals may have difficulties feeding and face starvation.

The transstadial persistence of tick-borne encephalitis virus in Dermacentor reticulatus ticks in natural conditions.

There are a number of reports regarding natural infection of Dermacentor reticulatus ticks with TBE virus; however, the transmission mode of TBE virus in this tick population has not been investigated. This study was conducted in Białowieża Primeval Forest, east Poland. Forty fully engorged nymphs of D. reticulatus were sampled from root voles (Microtus oeconomus). Ticks were kept until molting. All ticks were screened for the presence of TBE virus by nested RT-PCR. Three adult ticks were positive for infection with TBE virus. The present study for the first time demonstrates the possibility of transstadial mode of TBEV transmission in D. reticulatus ticks.