Search results for "Microtus"
showing 10 items of 59 documents
Stepes strupastu galvas smadzeņu, galvaskausu un apakšžokļu morfometriskā mainība guentheri grupā (Arvicolinae, Sumeriomys apakšģints) ģeogrāfiskās i…
2021
Šī darba mērķis ir galvas smadzeņu, galvaskausu un apakšžokļu diverģences izpēte pēc to ģeometriskās formas, pieciem strupastu “guentheri” grupas taksoniem ar ģeometriskās morfometrijas metodes izmantošanu. Papildus bija veikta smadzeņu lineārā morfometrija. Iegūtie dati rāda, ka dzimuma faktors neietekmē izpētīto taksonu galvas smadzeņu, galvaskausu un apakšžokļu formu, kā arī galvas smadzeņu lineāros parametrus. Starp divām sugām tiek atzīmētas ievērojamas atšķirības pēc galvas smadzeņu formas (puslodes, smadzenītes un ožas sīpoli) un lineārajiem parametriem (smadzeņu augstums, platums un garums). Atšķirības tiek parādītas arī galvaskausa un apakšžokļu formā. Katram taksonam ir savas īpaš…
Stepes strupastu galvas smadzeņu morfometriskā mainība guentheri grupā (Arvicolinae, Sumeriomys apakšģints)
2019
Šī darba mērķis ir galvas smadzeņu diverģences izpēte pēc to lieluma un ģeometriskās formas trim strupastu “guentheri” grupas taksoniem ar lineārās un ģeometriskās morfometrijas metožu izmantošanu. Iegūtie dati rāda, ka dzimuma faktors neietekmē izpētīto taksonu smadzeņu lineāros parametrus un formu, kas liecina par dzimuma atlases vāju iedarbību uz morfoloģisko pielāgojumu veidošanos un smadzeņu uzbūves mainību. Tiek atrastas būtiskas atšķirības strupastu galvas smadzeņu absolūtā un relatīvā masā (cefalizācijas indekss): vismazākā tā tiek atzīmēta M. guentheri, lielāka M. hartingi, bet savā starpā M. h. hartingi un M. h. lydius populācijas ievērojami diverģē. Visi lineārie mērījumi trim ta…
Stepes strupastu apakšģints Sumeriomys individuālās uzvedības pārmaiņas plēsonības riska ietekmē
2016
Šā darba mērķis bija apskatīt individuālo uzvedību stepes strupastu apakšģints Sumeriomys sugām motivācijas un dažādu plēsonības risku stimulu ietekmē. Pētījumā izmantota atklātā lauka metode un tās modifikācijas plēsonības riska ietekmes pētīšanai. Aprakstīta dzīvnieku individuālā uzvedība olfaktorā un vizuālā plēsonības riska ietekmē un jauna objekta un izsalkuma ietekmē. Atklātā lauka metode veiksmīgi aprobēta individuālās uzvedības un plēsonības riska ietekmes pētījumu veikšanai. Pētījumā izmantoto sugu uzvedība apskatīta skalā „pārgalvīgs – piesardzīgs” un indivīdi iedalīti trīs uzvedības grupās. Būtiskākā plēsonības riska ietekme novērota galējām uzvedības grupām – ekstrēmi pārgalvīgi…
Sex–biased maternal investment in voles: importance of environmental conditions
2004
Adaptive bias in sex allocation is traditionally proposed to be related to the condition of mothers as well as to the unequal fitness values of produced sexes. A positive relationship between mother condition and investment into male offspring is often predicted. This relationship was also recently found to depend on environmental conditions. We studied these causalities experimentally using a design where winter food supply was manipulated in eight outdoor-enclosed populations of field voles Microtus agrestis. At the beginning of the breeding season in spring, food-supplemented mothers seemed to be in a similar condition, measured as body mass, head width, body condition index and parasite…
Karyological and dental identification of Microtus limnophilus in a large focus of alveolar echinococcosis (Gansu, China).
1999
International audience; A study of voles (Arvicolidae, Rodentia) from Gansu (China) designed to identify a potential host of Echinococcus multilocularis, responsible for human alveolar echinococcosis, leads to a general analysis of Microtus limnophilus population karyotypes, M1 of M. oeconomus populations from all of Eurasia and of M. limnophilus of Mongolia. The Microtus of Gansu belonging to the nominal subspecies M. limnophilus limnophilus (2n = 38; NF = 58) differs markedly in size and shape of M1 from the M. limnophilus of Mongolia, which must therefore be considered as a new subspecies M. limnophilus of malygini nov. ssp. (2n = 38; NF = 60) and the M. oeconomus of Mongolia should be r…
Is there a linkage between metabolism and personality in small mammals? The root vole (Microtus oeconomus) example
2010
Significant inter-individual variation in the rate of animal metabolism is a widespread phenomenon that has started to accumulate general interest. Here we follow recent calls to focus on linkage between the variation in energy metabolism and animal personality. By using wild caught root voles as a study species, we examined the relationship between the behavioral patterns (assessed in open field test) and resting metabolic rate (RMR), both of which are known to show large individual differences and intra-individual consistency in voles. Our results showed only a weak relationship between personality traits and metabolism, since the most parsimonious model (according to AICc) explaining RMR…
Costs of coexistence along a gradient of competitor densities: an experiment with arvicoline rodents
2006
Summary 1 Costs of coexistence for species with indirect resource competition usually increase monotonically with competitor numbers. Very little is known though about the shape of the cost function for species with direct interference competition. 2 Here we report the results of an experiment with two vole species in artificial coexistence in large enclosures, where density of the dominant competitor species (Microtus agrestis) was manipulated. Experimental populations of the subordinate vole species (Clethrionomys glareolus) were composed of same aged individuals to study distribution of costs of coexistence with a dominant species within an age-cohort. 3 Survival and space use decreased …
Serological Survey of Rodent-Borne Viruses in Finnish Field Voles
2014
In northern Europe, rodent populations display cyclic density fluctuations, which can be correlated with the human incidence of zoonotic diseases they spread. During density peaks, field voles (Microtus agrestis) become one of the most abundant rodent species in northern Europe, yet little is known of the viruses they host. We screened 709 field voles, trapped from 14 sites over three years, for antibodies against four rodent-borne, potentially zoonotic viruses or virus groups: hantaviruses, lymphocytic choriomeningitis virus (LCMV), Ljungan virus (LV) and orthopoxviruses (OPV). Antibodies against all four viruses were detected. However, seroprevalence of hantaviruses, LV and LCMV was low. …
Breeding state and season affect interspecific interaction types: indirect resource competition and direct interference.
2011
Indirect resource competition and interference are widely occurring mechanisms of interspecific interactions. We have studied the seasonal expression of these two interaction types within a two-species, boreal small mammal system. Seasons differ by resource availability, individual breeding state and intraspecific social system. Live-trapping methods were used to monitor space use and reproduction in 14 experimental populations of bank voles Myodes glareolus in large outdoor enclosures with and without a dominant competitor, the field vole Microtus agrestis. We further compared vole behaviour using staged dyadic encounters in neutral arenas in both seasons. Survival of the non-breeding over…
Late Pleistocene (MIS 3-4) climate inferred from micromammal communities and δ18O of rodents from Les Pradelles, France.
2013
The middle Paleolithic stratigraphic sequence of Les Pradelles (Charente, France) spans from the end of Marine Isotope Stage (MIS) 4 until the middle of MIS 3. Micromammal remains are present in all the stratigraphic levels, offering a rare opportunity to address the questions of both environmental and climatic fluctuations throughout this period. Climate modes were studied through the taphonomy, biodiversity and oxygen isotope compositions of phosphate (δ18O p ) from 66 samples of rodent tooth enamel. The δ18O p values from the lower sedimentary levels provide summer mean air temperatures of 19 ± 2°C (level 2/1) and of 16 ± 2°C (levels 2A, 2B and 4A). Within the middle of sequence (level 4…