Zhurnal obshchei biologii最新文献

Developmental processes of cnidarians, the basal metazoan representatives, possess extremely high regulative ability. It is known that any isolated fragment of the freshwater polyp hydra's body can regenerate an intact animal. Moreover, in many cnidarian species, suspension of single dissociated cells can form aggregates, which regenerate normal body plan of polyp or medusa. This process can be considered as an extreme case of regeneration. The development of cell reaggregates of Hydra is a conventional experimental system to study the physical basis of morphogenesis. Investigations of the cnidarians' reaggregate development help to clarify basic rules and mechanisms of the metazoan body plan formation and the role of self-organization in the metazoan early development. In this review, we summarize the data revealed by dissociation - reaggregation experiments performed on the representatives of different cnidarian taxa. We also analyze the data on the morphogenetic and molecular basis of the reaggregate development from randomly organized group of cells to cnidarian-specific body plan.

Epigenetic phenomena are defined as morpho-physiological changes not related to impairments of DNA sequence. The results of our study indicate that a pulsed non-mutagenic thermal stress inflicted on developing ova (pro-embryos) gives rise to positive transgenerational epigenetic changes in the life span of offspring. At that, this effect depends on heterozygosity by lgl-mutation inherited from mothers. In generation Fl, determination of higher survival trait occurs even at early stages of oogenesis. The most pronounced effect is observed when heating is applied to the cells at the earliest stages of pro-embryo development. This study is the first experimental work on modeling the transgenerational aftereffects of pre-zygotic (pro-embryo) stress on offspring survivability and longevity when tumor suppressor lgl is operating. The significance of the results with regard to human epigenetics is discussed.

The hypothesis is suggested on the emergence of N2-fixing plant symbionts from soil diazotrophs and from the satellites of Glomeromycota fungi forming arbuscular mycorrhizae (AM). This universal form of plant-microbe symbiosis possibly appeared from integration of ancestral land plants (rhyniophytes, psylophytes) and microbial consortia composed of AM-fungi assimilating soil phosphates and bacteria fixing atmospheric CO2 and/or N2. Releasing of these bacteria from AM-fungal hyphae into the plant tissues elicited the selection of genotypes capable of the fungi-independent multiplication in planta, as well as the fixation in bacterial genomes of the genes for synthesis of chitin-like signal factors stimulating the development of symbiotic structures. An early stage of this evolution might been represented by formation of N2-fixing syncyanoses, the late stage - by formation of nodular symbioses of dicots from Eurosid I clade with rhizobia (α- and β-proteobacteria) and with actinobacteria Frankia. Emergence of these symbioses was possibly based on the migration of soil and endophytic bacteria into the storage organs (modified stems or lateral roots), where the optimal conditions were established not only for N2 fixation but also for the evolution of bacteria towards an increased symbiotic activity. This evolution resulted in the emergence of primary rhizobia (Bradyrhizobium, Burkholderia) which acted as the donors of sym-genes for a broad spectrum of microbes transformed into the secondary rhizobia (Rhizobium, Sinorhizobium). The succeeding evolution of nodular symbioses was directed at an increased efficiency of symbiotrophic nitrogen nutrition in host plants following two scenarios: (i) “expensive”, based on the increase of N2- fixing activity via transformation of bacteria into non-reproducible bacteroids; (ii) “economic”, based on acquiring the determinate nodule structure and ureide nitrogen assimilation.

Adaptation to stress factors is often accompanied by negative side effects that are manifested in lower fitness in the absence of the stress factor. This can lead to ecological specialization of the populations adapted to stressful environment and, ultimately, to ecological speciation. However, the existence of eurytopic species with a wide spectrum of ecological tolerance implies that adaptation to marginal conditions apparently can proceed without negative side effects or even involve positive effects, leading to niche expansion. Experimental evidence in favour of this evolutionary scenario is scarce. In the course of the evolutionary experiment that lasted for 20 generations, the laboratory populations of Drosophila melanogaster successfully adapted to stressful media with high NaCl concentration. The adaptation is manifested through the higher number of offspring produced during a fixed time interval by a pair of parents from the adapted lineages on the stressful medium compared to the control (unadapted) lineage, and in the less pronounced delay in larval development caused by high NaCl concentration. The adaptation to stressful medium did not entail fitness costs on the standard (favorable) medium; moreover, it resulted in more effective reproduction in favorable conditions (expansion of the trophic niche). These results, together with those obtained earlier during the study of adaptation of D. melanogaster to nutrient-poor starch based medium, imply that adaptation to marginal conditions accompanied by positive (rather than negative) side effects, leading to the expansion of the trophic niche, may be a frequent phenomenon in eurytopic species like D. melanogaster, probably explaining, to some extent, their ecological tolerance. Scarcity of experimentally confirmed examples of such evolutionary scenario is probably due to low number of attempts to find them. One possible mechanism of 'multi-purpose adaptations' obtained during the acclimation to environmental stress is the adaptive changes of symbiotic microbiota which, in Drosophila, is efficiently transferred between generations if offspring eat the medium on which their parents had lived. For instance, high quantities of symbiotic lactobacilli in the gut can enhance larval growth, life span of adults, and the efficiency of substrate utilization. Further studies are needed to reveal the mechanisms responsible for the changes in fitness observed in the course of the experiment.

In natural environment, stresses, when animals happen to be exposed to them, influence the functional activity of adrenal cortex. It can be expected that in animals, living under unfavorable conditions, basal concentration of glucocorticoid hormones would be increased while adrenocortical response to acute stress would be weakened. Since the main function of stress-reaction is resources mobilization meant to compensate an environmental impact, its weakening should lead to reduction of reserve metabolic capacities. To test this hypothesis, we compared energy metabolism, body temperature, and corticosterone concentration in blood plasma measured in northern red-back voles (Myodes rutilus) before and after acute cooling in helium-oxygen mixture. Voles belonged to two populations that deffered in relative abundance. It is found out that voles from a population of low relative abundance inhabiting the recreational forest of Novosibirsk Scientific Center, despite their being more stress-prone and having weakened stress-reaction, have higher maximum metabolic rate than voles from the mountain taiga polulation with high relative abundance. The results obtained suggest that living under unfavorable conditions leads to physiological adaptations which enhance resistance to acute stress, yet increase the risk of chronic stresses that have negative effect on fitness.

Starting from 2009, monitoring studies of swamp regimes have been conducted at the swampland station located in the north-eastern Altai. Here, we present the results of biological activity (indices of microorganisms abundance, respirometric indicator, catalase activity) in peat deposits of eutrophic (Turochak) and mesotrophic (Kutyushskoye) swamps during 2012-2013 vegetation periods with different levels of marsh water and oxidation-reduction conditions.

Observations of trail activity of the martens, mountain hares, and red squirrels in winter along fixed routes in the Central Forest Reserve showed its high variability and synchronism in time and space. Polynomial dependence of the trail activity and correlation between spatial distribution of marten, mountain hare and squirrel are detected. The influence of weather on the trail activity is smaller, but statistically significant. It is proved that the space-time dynamics of the trail activity is governed by the Moran effect which is amplified by relations between the predator and prey.

Using successional system of Stachyo sylvaticae-Tilietum cordatae association as a case study, the possibilities are considered of applying syntaxonomy as developed on the basis of floristic classification principles. Characteristics of restorative successions on cut-over lands have been analysed at strong and weak disturbance of soil cover as well as in plantings of coenotically weak species Pinus sylvestris and coenotically strong species Picea obovata. High self-restoring potential of the association studied is emphasised.

Detrended correspondent analysis is used for constructing an ecological ordination model of higher units of steppe vegetation in southern mountains of Middle Siberia. The model is based on 326 complete geobotanical descriptions and correlation analysis between the values of major axes and climatic, soil-ground, and geographical parameters. In the space of two first principal ordination axes, ecological series of steppe vegetation coenofloras are observed which are orientated along climatic factors of annual and seasonal precipitation, temperature, oceanity-continentality, and ground stoniness. A syntaxonomic interpretation of observed ecological-geographical steppe types is given, and the hierarchy of higher classification units is substantiated from the ecological point of view.

Mechanisms of interactions between species present one of the central problems of contemporary behavioral and evolutionary ecology. Field observations of possible resource redistribution and mutual behavioral adaptations between representatives of different guilds with substantially overlapping niche parameters are, so far, few. Using the methods of small mammals censuring, with account for their mobility and burrowing activity, at the sites with high and low dynamical density of wood ants Formica aquilonia, as well as in anthills proper, spatial interactions between these animals are revealed for the first time which are based on seasonal transformations of topic competition and synoecism. Species composition and domination structure of small mammals communities appear to be similar in those territories controlled by F. aquilonia and almost free of them. However, judging by animals’ spatial distribution and activity it can be suggested that wood ants, being a disturbing factor, markedly reduce the numbers and burrowing activity of small mammals in their territory and, apparently, hinder mammals dispersion. During seasonal resting of ants, when they move down into the soil, anthills attract a lot of small animals: from October to May up to 84% ant nests are burrowed by murine rodents and insectivore mammals. It seems to be possible that there are trophic relationships between small mammals and wood ants, with mammals consuming nest substrate as well as insects themselves.