The role of neighborhood relations in maintenance of the spatial-ethological structure of local settlements as exemplified by the water vole (Arvicola amphibius).

Adult males of the water vole have been found experimentally to recognize their neighbors and react to them differently depending on the degree of spatial proximity in nature. Most tensions (estimated by the number of aggressive acts in the encounters) were observed between distant neighbors (from neighboring settlements), which did not belong to the same groups with established hierarchy and a relatively reduced aggression. These are probably perceived as the most likely competitors (because of their spatial proximity). At the same time, male voles kept away from the obviously unfamiliar ones, though they do not express any apparent aggression.

Dynamics of testosterone concentration in male steppe lemmings (Lagurus lagurus) in the reproductive cycle reflects the species-specific mating system.

In the blood of male steppe lemmings, relatively low background levels of testosterone were detected, this is characteristic of a monogamous species. A significant increase in testosterone level, more expressed in sexually active males, was observed at the initial stage of formation of reproductive couples. Apparently, in the future, the couple will exist in a stable relationship, and, hence, the maintenance of a high testosterone level becomes excessive. The decrease in, and the relative "normalization" of, the hormone level during the existence of the pair, including raising of the young, promotes higher expression of the male paternal care of the offspring at the species level.

[Genetic-physiologic mother-fetus relationships and their effect on the adaptive traits of the offspring]. / Genetiko-fiziologicheskie vzaimootnosheniia mat'-plod i ikh vliianie na adaptivnye priznaki potomkov.

Using our own data and literature, we present analysis of genetic-physiological mechanisms providing for stable reproduction of mammals. Using multiparous species (such as minks, mice, water voles), we demonstrate that embryonic and early postnatal mortality of the offspring makes a significant contribution to stabilization of the actual fertility rate at a level optimal for the species. Studies of phenogenetics of fertility of inbred mice and their hybrids have demonstrated the definitive role of immunogenetic relationships between mother and fetuses in establishing of vitally important characteristics of the offspring. Antigenic differences between mother and fetuses observed in crosses between different strains and in experiments on allogenic transplantation of embryos provide stimulate the hormonal support of pregnancy (increase the level of progesterone) and the rate of embryonic development. It has been shown that antigenic stimulation of mother's immune system has a modifying effect on physiological and behavioral characteristics of the offspring and specifically on certain components of their reproductive success. In studies of the olfactory choice of mating partners by mouse and water vole females we established that mammals are capable of "predicting" the optimal phenotypic combination of parents leading to the most effective development of the offspring.

[Genetic-ecology monitoring of cycling populations of water voles (Arvicola terrestris L.) in the south of Western Siberia]. / Genetiko-ékologicheskii monitoring tsikliruiushchei populiatsii vodianoi polevki (Arvicola terrestris L.) na ioge Zapadnoi Sibiri.

Long-term studies on the role of the structural and functional organization of a population in reproduction control showed that the optimum level of reproduction is maintained via a complex of ethological, physiological, and genetic mechanisms. The coat color genes have a pleiotropic effect on the reproductive capacity of females and the potential for social dominance in males. The relative reproductive success of brown water voles is greater when the population size increases, whereas dark-brown individuals gain the advantage at peaks of population size. At the peak followed by a decrease in abundance, dark brown males usually held higher social ranks in the experimental groups. The results of field and laboratory experiments showed that high-ranking males gain reproductive advantage. Changes in the genetic structure in the course of population cycle depend on relative differences in fitness demonstrated by animals of different coat color under conditions of changing population size. The fact that females actively choose their mates is important for differentiation of males with respect to their adaptive value, prevention of inbreeding, and the maintenance of heterogeneity of populations as the basis of their stability.

Changes in aggressive behavior, thermoregulation, and endocrine responses in BALB/cLac and C57Bl/6J mice under cold exposure.

Effect of cold exposure on aggressive behavior, on the concentrations of testosterone and glucocorticoids, as well as on the oxygen consumption at different ambient temperatures, and calorigenic effect of noradrenaline have been studied in BALB/cLac and C57Bl/6J males. Under normal temperature conditions, there have been no significant interstrain differences. After cold exposure (5 weeks at 6-8 degrees C), C57Bl/6J mice exhibited more pronounced adaptive changes in thermoregulation and endocrine status (increase of glucocorticoids and decrease of testosterone concentrations were less expressed in C57Bl/6J than in BALB/cLac). At the same time, males of this strain demonstrated more intensive aggression than BALB/cLac mice. Some relations between physiological and behavioral changes caused by cold exposure are discussed.