Issues of under-representation in quantitative DNA metabarcoding weaken the inference about diet of the tundra vole Microtus oeconomus

During the last decade, methods based on high-throughput sequencing such as DNA metabarcoding have opened up for a range of new questions in animal dietary studies. One of the major advantages of dietary metabarcoding resides in the potential to infer a quantitative relationship between sequence read proportions and biomass of ingested food. However, this relationship’s robustness is highly dependent on the system under study, calling for case-specific assessments. Herbivorous small rodents often play important roles in the ecosystem, and the use of DNA metabarcoding for analyses of rodent diets is increasing. However, there has been no direct validation of the quantitative reliability of DNA metabarcoding for small rodents. Therefore, we used an experimental approach to assess the relationship between input plant biomass and sequence reads proportions from DNA metabarcoding in the tundra vole Microtus oeconomus. We found a weakly positive relationship between the number of high-throughput DNA sequences and the expected biomass proportions of food plants. The weak relationship was possibly caused by a systematic under-amplification of one of the three plant taxa fed. Generally, our results add to the growing evidence that case-specific validation studies are required to reliably make use of sequence read abundance as a proxy of relative food proportions in the diet.

Effects of short-time cold impact on hematologic chrarcteristics of tundra vole (Microtus oeconomus PALLAS)

Проведено изучение воздействия низкой температуры (-50С) в течение двух часов на гематологические показатели самцов полевок-экономок (Microtus oeconomus Pallas) разного возраста (2, 4 и 10 месяцев). Обнаружена зависимость проявления эффекта от возраста животных. В большей степени на общее переохлаждение реагировали полевки старшей возрастной группы. Установлено, что действие холода вызывает умеренную лейкопению и лимфопению у половозрелых животных (4 и 10 месяцев), а также понижение содержания тромбоцитов в периферической крови у 10 месячных самцов. Полученные данные свидетельствуют о чувствительности показателей периферической крови самцов полевок-экономок к кратковременному действию низкой температуры и являются отражением неспецифичных клеточных реакций. We studied the effect of the 2-hours exposure to the low temperature (-50°C) on the hematological parameters of male tundra vole (Microtus oeconomus Pallas) of different ages (2, 4, and 10 months). We found the relation of the effect on the age of the animals. Voles of the older age group responded to a higher degree to general hypothermia. The action of the cold causes moderate leukopenia and lymphopenia in mature animals (4 and 10 months), as well as a decrease in platelet content in peripheral blood in 10-month-old males. The data obtained indicate the sensitivity of the peripheral blood indices of male tundra voles to the short-term effect of low temperature. They are a reflection of non-specific cellular reactions.

Bison (Bison bison) activity fragments subnivean tunnels of small mammals

Ecological interactions between ungulates and small mammals are generally not well understood. Here, we report an observation of unusually extensive small mammal (likely Meadow Vole [Microtus pennsylvanicus] or Tundra Vole [Microtus oeconomus]) tracks above the snow, exiting from trails and bed sites created by Bison (Bison bison) in northern Canada. We believe that weather and snow conditions were optimal for this observation. Although alteration of above-snow activity of small mammals in response to snow compaction by ungulates is probably not a rare event, it is not often reported. The effect on voles of exiting their subnivean tunnels as a result of Bison activity is unclear, but may be detrimental to their overwinter survival. Ungulate activity compacts snow, fragmenting small mammal tunnels resulting in loss of their insulative value for voles, and making it harder for them to dig new tunnels. Clearly, determining the effect of snow disturbance by gregarious ungulates on voles or other microtines, particularly regarding their overwinter survival, requires detailed investigation. Nevertheless, this observation provides new information on the ecological interactions between ungulates and small mammals, particularly from the boreal forest, where such information is largely lacking.

PARASITES IN VOLES AT THE TERRITORY AROUND MAHNEVSKAYA ICE CAVE (PERM REGION)

Present study was carried out for the investigation of mammalians parasites formation in the territory of West Siberia and Ural. The analysis of parasitophauna of tundra vole (13 examples) and bank vole (20 examples) obtained from the territory around Mahnevskaya Ice Cave at the North of Perm region was performed. Corpses of rodents was investigated by the method of partial helminthological dissection. As a result, a distribution of intestinal helminthes at 38,46% in Microtus oeconomus and 20,0% in Myodes glareolus is found. The tundra vole is most infested by Notocotylus noyeri with an infection level at the 23.08% and Anoplocephalidae sp. with an infection index at the 15.38%. Hymenolepidid Cestodes are revealed only in the bank vole. All detected parasites are specific to voles of these species. That low level of infection as like an absence of parasites eggs in micromammalian coprolites from Midholocene cave sediments let conclude about comparatively recent establishment of parasitoses in two species of voles at the territory.

Larval spirurids in a supralittoral amphipod in the north-east of Russia and the identification of the intermediate host of Antechiniella septentrionalis (Spirurida: Acuariidae), parasitic in a tundra vole

The supralittoral amphipod Traskorchestia ditmari (Derzhavin, 1923) was identified as the intermediate host for Antechiniella septentrionalis Ivanova, Dokuchaev & Spiridonov, 2019, a parasite of the tundra vole Microtus oeconomus and Skrjabinocerca sp. (both Spirurida: Acuariidae) in Magadan Oblast in north-eastern Russia. Joint infection by both larval spirurids was not observed. The infective stage of A. septentrionalis was the encysted larvae, while larvae of Skrjabinocerca sp. were free in the amphipod's coelom. The identity of A. septentrionalis was confirmed using cox1 mtDNA gene analysis, performed on adult stages from a tundra vole and on larvae from amphipods. Possible transmission routes of A. septentrionalis are discussed.

First record of natural Baylisascaris transfuga (Ascaridoidea, Nematoda) infection in wild rodents

The intestinal parasitic nematode, Baylisascaris transfuga, was recorded in wild rodents for the first time. Representatives of four murid species (15 Myodes rufocanus, 10 M. rutilus, 3 M. glareolus and 27 Microtus oeconomus) were collected in the White Sea coastal habitats in the south of the Kola Peninsula, Russia in July 2015 and examined for parasites. Encapsulated nematode larvae were detected in the mesentery and the large intestine wall of one grey-sided vole (M. rufocanus) and one tundra vole (M. oeconomus). Based on morphology, the larvae were identified as belonging to the genus Baylisascaris Sprent 1968. The partial 18S rDNA sequence of the larvae from the voles was obtained and fully corresponded to the sequence of Baylisascaris transfuga in the NCBI GenBank. The ITS rDNA and CoxI mtDNA sequences these larvae were also similar to the respective B. transfuga sequences in GenBank. The presence of B. transfuga in wild rodents suggests that rodents can participate in the B. transfuga life cycle.

Antechiniella septentrionalis n. sp. (Spirurida: Acuariidae), a new intestinal nematode parasite of the tundra vole Microtus oeconomus (Pallas) (Rodentia: Muridae) in the north-east of Russia

Antechiniella septentrionalis n. sp. (Spirurida: Acuariidae) is described from the duodenum of a tundra vole, Microtus oeconomus (Pallas), collected in the Magadan region in the north-east part of Russia. It differs from A. suffodiax (Beveridge & Barker, 1975) and A. sertatum Smales, 1991 mainly in having a larger number of postcloacal papillae (5–6 pairs vs 4 pairs), a differently shaped left spicule, the disposition of precloacal papillae in two rows vs one, and oblong vs oval eggs. Other differences include the different disposition of ovaries in A. septentrionalis n. sp and A. suffodiax and the different structure of deirids in A. septentrionalis n. sp. and A. sertatum. The new species was characterized molecularly (partial sequences for 18S rRNA, 28S rRNA and cox1 mtDNA). The phylogenetic analyses performed showed the affinity of the new species to the members of the Acuariidae and other spirurid nematodes.

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 (2000-2003, 2005, 2007-2015 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 .