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The study of fecal compounds in lake sediments is one of the newest trends in paleo-limnology. Some stanols are produced by the intestinal microflora of animals from sterols found in food. Once in water bodies, these substances remain in bottom sediments for millennia, therefore they are biochemical indicators of fecal intake. In humans and animals, similar 5β-stanols are synthesized, but their percentages differ. The human intestinal microflora produces more coprostanol and epicoprostanol compared to other animals, so these 5β-stanols are used to reconstruct the history of the population of water bodies, as well as to assess the anthropogenic load. In the present work, using gas chromatography with mass spectrometric detection, the vertical distribution of fecal stanols and their precursor cholesterol in dated bottom sediments of Lake Shira (southern Siberia, Republic of Khakassia) for a period of about 2000 years was studied for the first time. It is shown that the relative share of coprostanol and epicoprostanol was higher in sediments corresponding to the periods when the anthropogenic load in the lake′s drainage basin was supposedly increased: during the heyday of the medieval state of the Yenisei Kyrgyz (9-11 centuries AD), during the period of mass colonization by the Russian population (17-18 centuries), as well as in the 19-20 centuries during the development of resort activities. The absolute content of all fecal stanols during the last hundred years is higher, which can be explained both by an increase in fecal inflows and by degradation of stanols, leading to a decrease in the content of fecal stanols in the underlying core layers. The results obtained can be useful for monitoring the efficiency of treatment facilities, as well as for identifying the historical dynamics of human presence in the lake′s catchment area.

The industrial chemicals alkylphenols are xenoestrogens, but the sublethal effects of these substances on aquatic animals are poorly studied. The aim of this work was to study possible metabolic and reproductive disorders in amphipods, on the example of the species Gmelinoides fasciatus from the Gulf of Finland of the Baltic Sea, after experimental exposure to 4- tert -octylphenol (4t-OP) from the group of alkylphenols. The mortality of G. fasciatus amphipods in the 4t-OP concentration range from 0.5 to 1000 μg/L after 96 hours and 7 days increased with increasing concentration. It was absent at 4t-OP concentrations of 0.5 and 5 μg/L. At a concentration of 4t-OP of 20 μg/L, after 7 days, the mortality of crustaceans was 20 %, and at its concentration of 100 μg/L, it was 60 %. When exposed to sublethal concentrations of 4t-OP (0.5 μg/L), these amphipods showed a decrease in sexual activity after one week of amphipods: only 25 % of amphipods retained precopulatory pairs versus 100 % in control. Under chronic exposure (28 days) to the lowest concentration, males showed signs of demasculinization (decrease in the width of the gnathopods and an increase in the depth of the coxal plates); females showed a decrease in the overall fecundity and irreversible disturbances in state of embryos, namely, a high proportion (>50 %) of embryos that stopped their development at different stages of organogenesis. The conducted study shows significant functional disorders of metabolic processes and reproduction in crustaceans even when exposed to non-lethal concentrations of octylphenol. These results confirm the high toxicity of this industrial pollutant, the presence of which in the aquatic environment can lead to irreversible changes in the biota.

Non-indigenous brown bullhead from two lakes of the Karelian Isthmus was studied in relation to 36 morphological features characterizing the shape of the body and head, the position of the fins, the number of finrays and vertebrae. The obtained results were compared with data for the collection materials and earlier published data for other parts of the species distribution range in order to assess the intraspecific differentiation and morphological plasticity of this invasive species. Meristic characters of individuals from geographically distant sites were quite similar and no difference between areas was found. On the contrary, significant differences in morphometric characters between samples from geographically remote water areas of Europe were shown, reaching the thresholds established for subspecies identification. The high level of morphometric variability in the invasive brown bullhead indicates a high phenotypic plasticity in external morphological traits responsible for fish locomotion, which is considered among factors contributing to its successful adaptation to new habitats and determining the invasive potential of this species.

Studies of the physiological state of three-year-old pikeperch from the lake (natural habitat), ponds and fish farm cages, showed significant differences in the size, mass, biochemical, hematological and histophysiological parameters of fish. Farmed fish have large sizes (length 26.2 cm, weight 242.1 g), comparable to the size of lake individuals (27.6 cm and 278.2 g, versus 23.7 cm and 162.6 g in pond pikeperch), high liver index values (3.68 versus 1.42 and 1.03 % in lake and pond fish, respectively), gonads (0.73 versus 0.15 and 0.08 %) and abdominal fat (8.61 versus 1.87 and 2.30 %). The chemical composition of the body of farmed fish is characterized by a large amount of lipids (9.4 versus 2.5 and 3.6 %, respectively) and nitrogen-free extracts (3.4 versus 2.5 and 2.4 %), muscle - protein (21.0 versus 19.0 and 19.2 %), liver - lipids (26.6 versus 11.1 and 7.5 %, respectively) and nitrogen-free extracts (9.6 versus 1.9 and 2.5 %), and low moisture content (51.7 versus 69.3 and 71.5 %), protein (11.2 versus 16.6 and 17.2 %), ash (0.9 versus 1.1 and 1.3 %) and vitamin C (67.5 versus 87.9 and 97.6 %). The fatty acid composition of muscle lipids of farmed fish was generally comparable to that of lake and pond fish - the main groups of fatty acids were at a similar level: polyunsaturated fatty acids in the range of 37.0-40.6 % of the total fatty acids, saturated fatty acids - 25.5-29.6 %, monounsaturated fatty acids - 28.0 and 23.2 % in farmed and lake fish, and 17.5 % in pond fish. The content of arachidonic acid 20: 4n-6 in farmed fish was extremely low (1.0 versus 8.0 and 11.5 % of the total fatty acids). Liver lipids of farmed fish contained a large amount of oleic acid 18:1n-9 (30.3 versus 16.2 and 15.0 % of the total fatty acids in lake and pond fish) and n-6 polyunsaturated fatty acids (17.5 versus 8.4 and 7.1 %), in particular linoleic acid 18:2n-6 (7.0 versus 1.9 and 0.2 %). The blood of farmed fish, compared to pond fish, differed in a lower content of hemoglobin (64.8 versus 74.8 g/l), an increased content of immature lymphocytes (11.6 versus 6.1 %) and immature erythrocytes (2.2 versus 1.1 %). The gonads of farmed fish were at stage III of maturity with an average oocyte diameter of 478.9 µm; lake fish had two stages of oocyte maturity - previtellogenic oocytes of protoplasmic growth, 62.7 µm in size, and significantly larger vitellogenic oocytes of trophoplasmic growth - 227.6 µm. In pond pikeperch, gonads corresponded to stage II of maturity and oocytes were 58.3 µm in size. Certain differences in pikeperch from lakes, ponds and farm conditions are associated with different conditions of fish keeping and feeding.

An analysis of the community of rodents and insectivores in five biotopes of the southern forest-steppe of the Northern Kulunda was carried out. High biodiversity is typical for the coastal strip with dense herbage near the lake, and low biodiversity is typical for the feather grass-forb steppe. At the beginning of the 21st century, there was a change in dominance in the community of small mammals, and the species richness increased. Of the five shrew species, only the common, tundra and lesser shrews inhabit all biotopes. Their total share in each biotope ranged from 16 % to 38 %. Among the 11 rodent species, the narrow-skulled vole is the dominant species. Its cumulative share in the community of small mammals was 38,3 %. This species is characterized by a peculiar cycle of abundance. The reduction of steppe habitats has led to a decrease in the number of steppe lemming and a change in its population cycle. The share of other rodent species in the community of small mammals is low.

In the northern spurs of the Manchurian-Korean Mountains (Primorsky Territory), an assembly of dung beetles, inhabitants of cow dung, was studied. Data on species composition, population dynamics, number and biomass of dung beetles are presented. A comparison of the assemblies of sheep and cow dung beetles in the conditions of the northern spurs of the Manchurian-Korean mountains showed that, despite the fact that these assemblies are geographically located in identical areas, formed on the basis of a common pool of species and have a similar species composition of beetles, the structural features of these assemblies, and also the dynamic processes taking place in them have significant differences. This is expressed in a richer species composition in cow dung, in the number of species in individual functional groups, in differences in dominant species, in features of the seasonal distribution of abundance and biomass (including the peak values of these indicators for individual functional groups of dung beetles), and in aggregate indicators of overlapping temporal aspects, ecological niches of coprophilous scarab beetles. It is suggested that the above differences are due to both the historical processes of the formation of assemblies and abiotic factors, first at all, by size and consistency of substrate.

The results of year-round bird counts conducted in Ufa every two weeks for three years (2012-2014), on routes with a length of 5 km in each of the five sites (multi-storey buildings, in areas of old and new individual buildings, on streets and in parks) are analyzed. The methods of cluster analysis revealed the main trends of seasonal and territorial heterogeneity of the bird population. The informativeness of the obtained representations is determined using linear qualitative approximation of community similarity matrices (one of the methods of regression analysis). The selected seasonal aspects are compared with the phenological division according to the seasonal development of nature. The orientation of the constructed graphs in the factor space is compared with the results of non-metric scaling. A map of seasonal and territorial heterogeneity of the surveyed ornithocomplexes has been compiled.

Semi-fossorial Sorex unguiculatus is a common shrew species in the central part of Northeast Asia, and the paper is devoted to elucidating its status in shrew taxocenes within the entire specified range. The configuration of the modern range of the long-clawed shrew differs from the generally accepted one and its formation occurred through distribution from two Late Pleistocene refugiums - mainland and island. According to the status of the long-clawed shrew in the taxocenes, three areas were distinguished: this species is a dominant in low-species insular taxocenes, a subdominant in multispecies taxocenes of coniferous-broad-leaved forests of the Ussuri Territory, and a minor one in the zone of interpenetration of nemoral and taiga vegetation of the left-bank part of the Lower Amur Region. Further northwest expansion of the long-clawed shrew is unlikely due to the specific requirements of this species for the type and structure of soils, which change significantly under the conditions of the appearance of permafrost, and coexistence with an ecologically close species, the flat-skulled shrew.

Small mammal communities in different sections of the Middle Ob valley (floodplain and terrace) are considered in the article based on the analysis of our own data and literature sources. Small mammals were captured using similar methods everywhere: metal cones were used that were dug into ditch with pitfalls or placed along polyethylene film fences. During the period 2004-2022, we counted 16517 individuals of 21 species in the Middle Ob valley within the Khanty-Mansi Autonomous Okrug - Ugra. A total of 28-29 species of insectivores and rodents were recorded in the southern taiga and middle taiga areas of the Middle Ob valley. The lack of specificity in the number of animal species is determined by the fact that at present there is no complete clarity for the studied area with respect to voles of the “arvalis” group. Essays are given for all species encountered, describing the occurrence, abundance, and other aspects of small mammal ecology. The specifics of the southern taiga and middle taiga sections of the Middle Ob valley, as well as the floodplain and terrace as a whole, were revealed. Only in the southern taiga section of the Middle Ob valley, the common hamster, narrow-headed vole (southern subspecies), Korean field mouse, and herb wood mouse, which are not common in the middle taiga sections of the studied area, are found. These same species also avoid floodplain biotopes. The list of dominant species was determined for the floodplain - the common shrew and the root vole, for the terrace - the common shrew and the Northern red-backed vole. The co-dominant species are the Eurasian pygmy shrew and Laxmann’s shrew, as well as the harvest mouse. The valley of the Middle Ob is dominated by western Palearctic species. They tend to dominate both the floodplain and the terrace.

Sakhalin meadow communities are an important component of the vegetation cover of the Far East. The use of phytoindication scales is a possible way to understand the ecology of meadow vegetation. The material of the study was 113 geobotanical descriptions of meadow communities in the southern part of Sakhalin. A similarity matrix of descriptions was calculated by using the quantitative Bray - Curtis index for cluster analysis with the subsequent classification of meadow communities. For the first time, an ecological assessment of meadow vegetation in the southern part of Sakhalin Island was carried out using the scales of I. A. Tsatsenkin and D. N. Tsyganov. As a result of the work, the following meadow communities were identified: Phalaroides arundinacea meadows, seeded forb-grass meadows, coastal forb-grass meadows, floodplain-coastal tall grass meadows, Leymus mollis meadows, Aquilinum pteridium meadows, an Artemisia meadow. It was determined that the meadow communities of the southern Sakhalin are classified as moderately humid with the dominance of eumesophytes and xeromesophytes. Soils, even on the sea coasts, are non-saline, quite rich in nutrients and, at the same time, poor or sufficiently supplied with nitrogen. According to the calculations, the soils under the meadows are acidic and slightly acidic. The climate was defined as subboreal, with a surplus of precipitation. As for the agricultural use of meadows as pastures and hayfields, it has almost no effect on the composition of phytocenoses, however, low indicators on the scale of pasture digression may be a sign of violation of haymaking terms. The discovered feature of the Sakhalin meadow communities is that groups of meadows different in location and species composition, display very similar habitat conditions.