The relationship between parental responsiveness of bank vole males and their body weight, testes mass, and plasma and gonadal testosterone levels were examined. Two groups of voles were studied: Group I consisted of 14 breeding pairs where females gave birth to young within a month after formation of pairs, and Group II represented 13 pairs without offspring and signs of pregnancy in females. Males in Group I, unlike those in Group II, had contact with pups before the tests on parental responsiveness. In Group I, males were found to have larger testes and to exhibit a higher level of care-giving activity (pup retrieval) as compared to males in Group II. Both the plasma and gonadal testosterone levels in males exhibiting pup retrieval were revealed to be significantly higher than those for males exhibiting infanticide. Thus, promiscuity, competition for receptive females, and a higher level of testosterone secretion, which are characteristic of bank vole males during the breeding season, are not out of the realm of possibility of the males that care for young. Our findings suggest that factors promoting parental responsiveness in bank vole males are sensitization due to contact with pups and an increase in testosterone secretion. Obviously, there is a need to reexamine the role that testosterone plays in regulating rodent parental behavior.

The possibility of identification of the sibling species of Chiroptera by the example of Myotis daubentonii Kuhl, 1817 and Myotis petax Hollister, 1912 by their host-specific ectoparasitic fauna is discussed. Their habitat limits are defined.

Freshwater mollusks belonging to 17 species, in 7 families are examined purposely to search for spirochete bacteria in their crystalline style of the digestive system. As result of this study spirochetes are recorded in gastropod families Amnicolidae, Bithyniidae, Baicaliidae and Benedictiidae, represented by 12 species, occupying different habitats. Gastropods belonging to Valvatidae, Lymnaeidae and Planorbidae, characterized by lack of crystalline style did not include spirochetes in their stomachs. Studied gastropods having spirochetes or free of them are grazers or filter-feeders and mainly phyto-detrito-bacteriaphagous.

The dynamics of expression of the RT1A antigen of the class I major histocompatibility complex (MHC) in a Walker 256 tumor after its transplantation into Brattleboro rats with a genetic defect of Arginine-Vasopressin synthesis in the hypothalamus was studied. Expression of the RT1A antigen was detected by means of Western-blotting and flow cytometry in the tumor cells on the 14th-17th days after transplantation. In addition, a simultaneous increase in the portion of cells that express the RT1A antigen and in the level of its expression per cell was observed. It is presupposed that at a deficiency of Arginine-Vasopressin, a renewal of expression of the class I MHC antigens, which results in an increase of immunogenicity of this tumor and regression, occurs in the Walker 256 tumor in the Brattleboro rats.

The concept that the mechanisms limiting immigration of new Lepidoptera species are analogous for islands with different ages and degrees of endemism of their biotas is discussed. Specific features of individual species play a key role in establishment of the fauna and population on small islands rather than competitive interactions between these species. It is most likely that the species stably coexisting on an island will display similar ecological characteristics and life cycles, which complies with the concepts of the neutral theory of biodiversity and biogeography.

The variation of reproductive strategies in different populations of river perch and intrapopulation groups differing in the rate of growth have been analyzed. Using a bioenergetic approach, the origin and differences between these groups have been studied. It was shown that bioenergetic mechanisms of regulation of the sizes and weight of the eggs lead to formation of the strategy of forced reproduction in the slow-growing group of perch, unlike the reproductive strategy of the fast-growing group of perch characterized by a later reaching of sexual maturity at a greater relative weight of gonads and spawning of larger eggs, which provides for a longer lifespan of larvae. The great number of age groups in the spawning part of this group compensates for a decrease in reproduction in years with unfavorable conditions.

Size sexual dimorphism was investigated on 695 skulls of four Mustelidae species. By extent of increasing of differences between sexes the species are placed in following order: European pine marten (Martes martes), European mink (Mustela lutreola), American mink (Neovison vison), and European polecat (Mustela putorius). Extent of the dimorphism characterizes ecological plasticity of the species and is population characteristic. It is shown that M. martes takes specific and relatively narrow ecological niche of forest ecosystems, entering into weak competitive relationships with smaller Mustelidae species. The level of sexual dimorphism of M. lutreola, N. vison and M. putorius reflects intensity of its interspecific relationships within study area. High level of sexual dimorphism of M. putorius is determined by further divergence of ecological niches of males and females, and also appears to be compensatory mechanism reducing consequences of hardened environmental requirements.

The karyotype of Mustela kathiah was first described. Its structure is most similar to the karyotype of M. altaica, differing inthe morphological peculiarites of five pairs of large chromosomes. A comparative analysis of mitochondrial genes in the species Mustela allowed us to clarify understanding of the place of M. kathiah in the system of the genus. The earlier hypothesized proximity of the species to a group of small weasels (altaica, nivalis) or to a group of South Asian species (strigidorsa, nudipes) was not confirmed. A high level of differences between M. kathiah of Vietnam and specimens from southern China in nucleotide sequences of the cytochrome b (7.7%) and ND2 (6-6.2%) genes was found. Perhaps these differences, manifested in populations of M. kathiah from different regions, are adaptive.

This study was conducted in 2005 near Medusa Bay (73 degrees 21' N, 80 degrees 32' E) and the delta of the Pyasina River (74 degrees 10' N, 86 degrees 45' E), northwest of the Taimyr Peninsula. It was shown that in the years when the numbers of the Arctic foxes are high, even though the lemming numbers are high as well, Brent geese nest considerably closer to owls' nests than in the years with low Arctic fox numbers. At values of the Arctic fox densities greater than one breeding pair per 20 km2, the factor of lemming numbers ceases to affect the distance between owl and geese nests. This distance becomes dependent on the Arctic fox density (numbers). When the Arctic fox density is greater than the pronounced threshold, the owl-Brent internest distance is inversely and linearly related to the Arctic fox density.

Specimens sampled in Central Mongolia have been examined for the intraspecific polymorphism of the nucleotide sequences of ribosomal DNA internal transcribed spacers (ITS-1 + 5.8S + ITS-2) of the parasitic nematode Haemonchus contortus. A considerable diversity of haplotypes differing in the nucleotide composition of this DNA region has been observed. The phylogenetic relationships between the haplotypes detected in Central Mongolia and the corresponding sequences from other parts of the nematode distribution area (deposited with the NCBI GenBank) have been analyzed. Significantly different sequences have been found along with the haplotypes already observed in H. contortus or differing from them by one-two nucleotides.