Winter Reproduction of Cyclomorphic Mammals: From a Case to the Phenomenon.

In 2010 (a year of drought), the true winter breeding (TWB) of the pygmy wood mouse (S. uralensis) was first recorded in the Southern Urals and confirmed by the morphological parameters and age markers. The young born in winter fulfilled successfully their reproductive potential under favorable climatic conditions. The true winter breeding and the age cross of animals during the year of drought promoted the maximum population growth and enhanced population genetic heterogeneity. In subsequent years, TWB of S. uralensis became common, which is regarded as a climatic pattern. Extreme drought rearranged the rodent community and caused TWB of S. uralensis, which resulted in a higher abundance of the species.

Adaptation of small mammals to radiocontaminated environment: Oxidative metabolism and radioresistance.

Differences in radioresistance and oxidative metabolism parameters in rodents of different ecological specialization in the East Ural radioactive trace (EURT) area are shown. Northern mole voles (radiosensitive species) exhibit a pronounced resistance to chronic exposure to radiation, living in a series of generations in a radioactive environment, whereas pigmy wood mice (radioresistant species) are less resistant in the EURT area due to their migration activity. Thus, under the EURT area conditions, northern mole voles realize the genotypic radioadaptation, whereas pigmy wood mice realize the physiological radioadaptation, the key role in which is played by the ecological and physiological characteristics and the lifestyle of animals.

[Analysis of Microsatellite DNA in Rodents from Eastern Urals Radioactive Trace Zone and Contiguous Territories].

The variability of four microsatellite loci of rodents, caught from the head part of Eastern Urals Radioactive Trace (EURT), along with the rodents inhabiting contiguous zone with background radiation level and distant-reference territory, was analyzed forthe first time. Differences in the parameters of genetic diversity between northern red-backed voles from the EURT zone and from the reference population were detected. An increase in some indices of genetic diversity in animals from a contiguous to the EURT zone was found; this is probably associated with animal migration and configuration of the area of pollution. A transfer of radiation-induced effects to the contiguous territories and a decrease in the possibility of fixation of adaptations in a series of generations of mobile rodent species in the area of local radioactive pollution are consequences of migrations. The results of the study make it possible to recommend microsatellite markers for the analysis of radiation-induced effects in rodents as model objects of radioecological monitoring.

[Role of polyalternativeness of animals' ontogeny development in the estimation of ionizing radiation consequences].

The role of polyalternativeness of small mammals' ontogeny development (belongings of individuals to alternative pathways of the ontogeny development) in the estimation of effects of ionizing radiation is considered. It is shown that biological consequences of acute (laboratory experiment) and chronic (inhabiting the Eastern Urals Radioactive Trace zone) ionizing radiation in rodents significantly depend on the belonging of individuals to the pathway of ontogeny. Specificity of the response of the population to acute and chronic irradiation is revealed. It is concluded that it is necessary to take into account the belonging of individuals to the pathway of ontogeny development in a wide spectrum of investigations at the analysis of any biological parameters in small rodents in the zones of local technogenic contamination.

[Migration of rodents in the Eastern Urals Radioactive Trace zone (radiobiological aspect)].

We investigated migrations of mouse-like rodents in the Eastern Urals Radioactive Trace (EURT) zone using the method of small mammal group marking by tetracycline (additionally to the data of radionuclide self-marking). The originality of small mammals' population in the EURT zone is defined by a configuration of radioactively polluted area and features of animals' migrations. The tetracycline label is detected in the dentine of upper incisors fluorescing in UV light. A high migration activity of rodents is observed both in the EURT zone and adjacent areas. When migrating, rodents used the certain ways of moving. Our new data allowed us to conclude that the EURT zone, as well as any other areas, is inhabited by a population with a constantly changing set of individuals, i.e. a flowing population. It is the convincing evidence of the absence of any isolation. Migrations of small mammals in the narrow and extended EURT zone (1) considerably decrease the probability that certain adaptive changes may be fixed and inherited in a series of generations; (2) are the base of transmission of radio-induced effects in adjacent areas. The fact of a flowing population should be taken into account in a wide spectrum of investigations when analyzing the remote consequences of chronic radiation influence.

[The cytogenetic consequences of chronic irradiation in rodent populations inhabiting the Eastern Urals Radioactive Trace zone].

In bone marrow cells of rodents (Apodemus (Sylvaemus) uralensis Pall., 1811, Apodemus agrarius Pall., 1771) inhabiting the Eastern Urals Radioactive Trace (EURT) zone (Kyshtym radiation accident 1957) and adjacent areas of Urals, the chromosome instability and 90Sr accumulation in bones were investigated. Intensive mutagenic process in both species from impact plots (the soil pollution by 90Sr 2322-16690 kBq/m2) was found. Significant positive correlation of aberrant cells frequencies and 90Sr was shown. Possible causes of the lack of resistance to long-term mutagenic factor (over 100 generations since 50 years from the accident) such as migration of animals and specific configuration of the EURT zone (narrow extended territory with sharply falling gradient of radionuclide pollution), which considerably decrease the probability that certain changes will be fixed and inherited in a series of generations of rodents, are discussed.

[On the problem of radioadaptation in small mammals (ecological specialization of species, radioresistance, hemopoiesis, immunity)].

The data illustrating ambivalent nature of radioresistance of rodents having different ecological specialization: wood mice (Apodemus uralensis Pallas 1811) and mole-voles (Ellobius talpinus Pallas 1770) to acute (laboratory experiment) and chronic (long-term inhabiting the East Ural Radioactive Trace - EURT) radiation action are presented. These species are greatly distinguished by a way of life, a migratory activity, an average life span etc. Numerous immunological, hematological disturbances were found in more radioresistant wood mice inhabiting in radioactively-polluted biogeocenosis (density of pollution 90Sr - 18.5 MBq/m2 = 500 Ci/km2). On the contrary there are no pathological shifts in more radiosensitive mole-voles from the EURT zone (density of pollution 90Sr - 37 MBq/m2 = 1000 Ci/km2). Comparative analysis of the hematological and immunological parameters and absorbed dose loads in rodents from radiocontaminated environment testify about the possibility of radioadaptation in a series of generations in Ellobius talpinus Pall. The leading role in development of radioadaptation of mole-voles belongs to ecophysiological peculiarities of the species.

[Biological characteristics and ecological factors determining mammalian radioresistance in the Rodentia order]. / Biologicheskie kharakteristiki i ékologicheskie faktory, opredeliaiushchie radiorezistentnost' melkikh mlekopitaiushchikh otriada Rodentia.

Both the results of our investigations and published data on mammalian radioresistance, biological characteristics and ecological factors which modify it are generalized in this paper. The described diversity among large taxa in radioresistance is based on the data obtained on the rodents from the Old and the New Worlds (totally 51 samples from 22 genera of four families--Sciurudae, Muridae, Cricetidae, Heteromyidae). It was found that radioresistance substantially depended on which family the species belonged. The main biological characteristics and ecological factors (body size, nutrition type, biotopical restriction) were revealed; in sum they determined 40% of radioresistance of small mammals.