Contents of Proceedings of the Zoological Institute

This review deals with the topics of bird migration research that have seen significant progress in the recent years. In these fields, earlier views have been significantly re-considered. They include the manifestation of migration, i.e. length of migratory flights, their speed, duration of stopovers, flight altitude, which taken together form the spatio-temporal realization of migration. New data on this array of research questions make it possible to ask new questions about physiological adaptations that make such flights possible, and factors that govern these processes. Significant progress is also evident in the study of long-distance orientation and navigation of migrating birds. However, it mainly concerns the mechanisms of magnetoreception and use of magnetic cues for orientation. Besides, students of bird migration could not ignore the ‘-omics’ revolution, which, like the studies of the manifestation of migration, was mainly caused by technological advances, mainly by the advent of next generation sequencing techniques. The new data obtained by these methods raised the hope to sort out the genetic basis of endogenous control of bird migration. However, the gap between the expectations and the actual results remains. To close this gap, new research into the molecular and cellular mechanisms that underlie migratory behavior is necessary. The results available now mainly refer to the processes that are relatively well understood, mainly the mechanisms of energy turnover and stress response.

The atlas was prepared from the data on ring-recovery database of the Bird Ringing Centre of Russia (Institute of Ecology and Evolution of the Russian Academy of Sciences). We plan to publish an extended version of the atlas on the base of bird ring-recovery data. The Atlas will consist not only description of the migratory routes but a consideration of several population parameters of the focal species, as well as, the spatial distribution characteristics of recoveries and even probable practical use of the obtained population parameters values. More than 42000 ring recoveries of 36 European waterfowl species were used. Besides the standard description of the migratory routes, monthly distribution of recoveries, maps of direct and indirect recoveries, etc., the Atlas contains some additional information. In particular, the population structure of species: geographical populations were revealed. It is known that these populations served as a basement of the flyway conception. Then we elaborated math model allows calculating mean yearly mortality rate for each species, in different periods, males and females, etc. Ring-recovery data of a number of species shows the influence of the global warming on the waterfowl. Wintering sites usually are permanent; however breeding places shift more and more to the north. Therefore, mean distance between wintering and breeding places progressively increasing during 20th and the beginning of the 21th century. In addition, the distribution of recoveries in relation to each other along the area was described: 1) it was possible to calculate the degree of aggregation of recoveries (aggregation) for the species with the most numerous recoveries, specifically – to calculate the mean distance from each recovery to its nearest neighbour (mean minimal distance between recoveries); 2) degree of recovery concentration in groups (concentration) with different number of recoveries that located at not more than some distance (might be called as “key distance”) from each other. The distance between recoveries within such groups is less than the distance between groups (clusters). The distribution of recoveries in connection with ecological capacities of the area where these recoveries are located is described for the first time. The distribution of recoveries by their proximity to the different waterbodies is compared: to small and big rivers, lakes, and to the seashore. The exploratory analysis of the separate and mutual numbers dynamics in the two systematically close waterfowl species was performed.

The Taimyr Peninsula is a key region for reproduction of waterfowl of European and Asian wintering populations. The uniqueness of Taimyr is that birds migrate there from both the west and the east, following five out of eight global flyways: East Atlantic, Black Sea/Mediterranean, West Asian/East African, Central Asian, and East Asian/Australasian. The study develops the topic of conservation ornithology and sustainable use of biological resources raised at the First All-Russian Ornithological Congress by Dr. Evgeny Syroechkovsky. Russia lacks the system of state monitoring and assessment of waterfowl populations, in particular with the use of aerial survey methods. In 2019, counts of geese in the tundra zone of the Taimyr Peninsula were carried out from the board of an ultralight aircraft specially designed for aerial surveys. New data on the abundance and spatial distribution of geese were obtained. We substantiated the methodology for the survey flight routing with no transects and the use of GIS, remote sensing, and generalized additive models (GAM) for interpreting the results and extrapolating estimates of goose abundance. A database of the results of aerial surveys was compiled (http://rggsurveys.ru). According to our estimate, for the first time made by statistical modeling for the tundra zone of the Taimyr Peninsula, more than 1.5 million White-fronted geese, about 450000 Bean geese, 78400 Red-breasted geese, and 43000 Lesser White-fronted geese nest and moult on Taimyr. Comparison of these figures with modern estimates of the world populations of these species demonstrates the key role of the Taimyr Peninsula in maintaining populations of rare and economically important Anseriformes.

The distribution of birds in the West Siberian plain in the western part of the forest-steppe zone (bound east by River Ishim) is very dynamic. Just since the beginning of this century, 16 new breeding species and one possibly breeding species have been discovered in this region. Most of them (76%) are representatives of the Tropical group (5 species) dispersing from the south, as well as the Nomadic (5) and the European (3) types of fauna coming from the south and the west; 3 species belong to the Chinese type of fauna and one – to the Siberian type. Another new species from the Tropical group was recorded as breeding in the last decade of the previous century. The distribution ranges of all 6 representatives of the Tropical group and 2 species of the Nomadic fauna associated with aquatic habitats have expanded northward most over the past 40 years (for 500–600 km). A powerful wave of their dispersal in forest-steppe occurred during the years of maximum filling of water reservoirs in the early 2000s. At the same time, despite the cyclical dynamics of the water level, cyclical processes in the changes of the distribution of limnophile birds are not expressed (analysis of century-long faunal lists shows the cyclical nature of the distribution of no more than 2–3 such species). It is assumed that against the background of intense climate warming most bird species, primarily limnophiles, are not simply redistributing individuals within the ranges, but are expanding their ranges northward, and that expansion will continue in the future. The anthropogenic impact on the regional avifauna is mainly caused by the consequences of the economic crisis in agriculture. In the recent decades, it has been much less obvious than the natural impact.

Here we discuss the main stages in the study of the morphology of the avian hind limbs as an example of the historical development of morphological studies in biology: from illustrations at the level of a work of art, through the collection of anatomical material and its functional interpretation to the reconstruction of hypothetical and real forms. We provide a synopsis of original studies, describing the stages in the evolution of jacanas and trogons, as well as the key locomotor adaptation of passerine birds. Reconstructions of the soft tissues and ligaments of the hind limbs of the Hesperornis, moa, and Haast’s eagle make it possible to judge the peculiarities of locomotion in extinct species.

On Earth, billions of birds make seasonal migrations every year. Some species fly thousands of kilometers, overcoming seas, mountains and deserts on their way. For migration to be successful, birds must have perfect mechanisms for controlling its beginning, duration and termination. On the way, birds have to make many decisions: how much in energy reserves to accumulate; when to depart, how long and in which direction to fly; how to select optimal weather conditions for flight; and, finally, when and where to terminate migration. Prior to migration, birds develop a migratory disposition – a suite of changes in physiology and behavior (e.g. migratory fattening and expression of nocturnal migratory activity) which are typical for this important life-history stage. Such physiological changes and migratory behavior are the subject of hormonal regulation. The central structure that controls activity of various hormonal systems and development of migratory disposition is the hypothalamic-pituitary system. The hypothalamus controls the secretion of regulatory hormones by the pituitary gland and these hormones, in turn, regulate the activity of downstream endocrine glands. It has been established that spring migratory disposition is triggered by an increasing photoperiod, which stimulates the production of testosterone, prolactin and modulates the signaling of thyroid hormones. In contrast, it is practically unknown how autumn migratory disposition develops when the photoperiod decreases and does not stimulate release of the abovementioned hormones. While in migratory disposition, the endocrine control of behavior on the smaller temporal scales (for example, the level of fuel accumulation, or decision to depart from a migratory stopover) is associated with the combined action of melatonin, corticosterone, insulin, glucagon, adipokines, and other hormones and neurotransmitters. In this review, I will describe the role of these hormones in the control of migratory traits, highlight the existing inconsistencies, and present possible ways to progress in this area of research. A knowledge of endocrine regulation of migratory behavior will help to predict the limits of species adaptability, explain current population trends, and inform conservation actions, which is especially important in the light of modern climate change and anthropogenic transformation of landscapes.

Dung beetles are important elements in the food webs in Madagascar, where they evolved as consumers of lemur excrements. The anthropogenic pressure reduces lemur populations, which causes dung beetles to shift to other food sources. To assess the diet of giant Madagascan dung beetle Helictopleurus giganteus (Harold), we studied hindgut content of seven specimens from different localities with amplicon metagenomic methods. We found reads of five mammal species, with over 99% of total reads belonging to human and cow. No native Madagascan mammals were detected in the samples. The results suggest the human mediated diet shift in H. giganteus, although they should be interpreted with caution, because unavoidable contaminations may contribute reasonably to the high yield of the cow and human reads.

The article is devoted to three aspects of the study of free-living freshwater nematodes: 1) the taxonomic position and validity of the genus Raritobrilus due to the unjustified synonymization of this genus; 2) the redescription of the species R. scallensis due to its incomplete primary description and the reduction of the species R. husmanni to synonyms of R. scallensis; the basis for this synonymization was a comparative analysis of the morphology of these species; 3) replenishment of the list of nematofauna of Lake Ladoga.

In the Mediterranean Anatolia, the Lakes Region and Konya Closed Basin are the richest regions in terms of endemic fish with 55 species. An important place among them is occupied by the Oriental killifish genus Anatolichthys (Cyprinodontiformes: Aphaniidae). Many of them are still poorly understood. In these regions, global warming (droughts) and anthropogenic impact are serious threats to freshwater fishes. We have studied little explored populations of endemic A. maeandricus in Işıklı Lake and Işıklı Spring (Büyük Menderes River basin), influenced by both factors. Sampling was carried out seasonally (August, October 2021, February and April 2022), with a total of 233 and 157 specimens. Age ranges, male to female proportions, length and weight ranges were determined for two populations. The Von Bertalanffy growth equations were calculated for the populations in Işıklı Lake and Işıklı Spring, respectively, as Lt = 22.58 (1-e^{–0.0408(t+-0.303)}) and Lt = 27.60 (1-e^{–0.0304(t+0.554)}). The content of the digestive tract and stomach was examined. Gammarus sp. and Chironomid organisms were dominant in food of fish from both habitats. Although the growth parameters appear to be positive, drought and habitat destruction can be expected to endanger this endemic species in the near future. By our observations, over the past ten years, the habitat of the species has been severely restricted, and this situation has also affected other endemic fish species in the region. For these reasons, it is an urgent to protect the habitat of endemic fishes first and then the species themselves.

Climatic changes are manifested through temporal shifts of seasonal events in environment, which may be critical for planktonic organisms. Temporal shift of seasonal warming curve in high latitudes affects phenology of aquatic organisms. Significant correlation between timing of phenological events in the life cycles of planktonic copepods and spring-summer temperature transition dates was revealed by canonical correlation analysis. We analyzed the long-term zooplankton and temperature time series (1961–2018) from the White Sea (66°19'50"N; 33°40'06"E, near the White Sea Biological Station of the Zoological Institute of the Russian Academy of Sciences). Two types of seasonal abundance dynamics of copepod juveniles and four types of the spring to summer transition were revealed. Each species demonstrated specific dynamics in response to each type of spring to summer transition. Species with similar ecological traits differed in their phenological response to the changes in the temperature dynamics. This phenomenon was explained, at least partly, by niche partitioning, when temporal niches of ecologically similar species were separated as a result of shifting the phenological events in time. The latter, in turn, was the result of organisms’ response to changes of spring to summer transition dynamics from year to year. We hypothesize that such separation may be one of the solutions of the “Paradox of the plankton”, favouring success of species-rich planktonic communities in high-latitude ecosystems, characterized by relative paucity of food resources and short productive season.

The changes in the main nutrients – phosphorus and nitrogen, as well as the quantitative and structural characteristics of the phytoplankton of the Volgograd Reservoir in 2001–2021 are shown. Under the conditions of global climatic transformation, we recorded changes in the thermal regime, intra-annual redistribution of water runoff, decrease in precipitation, negative trends in dissolved ammonium and nitrates. In the genesis of phosphates, the role of internal water processes decreased and the influence of hydrological factors increased. Negative trends in the total biomass of phytoplankton, as well as diatoms and green algae, have been found. At the same time biomass of Cyanobacteria increased. The ratio of taxonomic groups of phytoplankton has changed: the proportion of diatoms has decreased with an increase in cyanobacteria, cryptophytes and dinophytes. These negative trends in pelagial can be considered as the processes of regressive succession inside the biggest cyclic processes, and could be caused by changing climatic conditions. At the same time, the increase in the biological activity of benthal communities (higher aquatic vegetation) indicates the ongoing eutrophication of the reservoir according to the macrophyte type.

The studies conducted in spring have shown the main trends in changes in the structure of zooplankton in the kultuk zone of the Volga River delta in years that differ in hydrological and temperature regimes. It was revealed that in low-water years (2012, 2014), with a decrease in the volume of runoff, water level, and a reduction in the duration of floods, zooplankton was characterized by relatively low species richness, high biomass of Copepoda and Cladocera. At the same time, the highest rates of specific species richness, biomass and abundance of all zooplankton groups were observed at spring of a low-water year (2014), which was characterized by a runoff volume during the flood of 101 km³, a high pre-flood water levels, the absence of a sharp and significant dilution, as well as an early warm spring and gradual warming of the waters. In the year (2012), characterized by a volume of runoff during the flood period of 114 km³, a decrease in water level and a sharp increase in temperature before the flood, and then its rapid rise with dilution by cold waters, zooplankton was distinguished by the minimum species richness, a low number of ecological groups and low abundance of Cladocera, but a high proportion of juvenile copepods (fine filter feeders) and in terms of biomass of active euryphagous predators and euryphagous collectors. In a medium-water year (2013) with a large volume of runoff during the flood of 140 km³, with early and high and long floods, zooplankton was distinguished by a high total number of species encountered, but a minimum abundance and biomass, which is associated with the “dilution effect” and an increase in the areas of flooded rich in higher aquatic vegetation.

With an increase in altitude, both abiotic and biotic conditions in mountain watercourses change. To assess the features of spatial distribution of macroinvertebrates as well as to identify the driving factors of this dynamics, the data on species richness, abundance and biomass of EPT taxa (mayfly, stonefly, caddisfly) from 21 small mountain rivers of Altai were analyzed. By location, all rivers were divided into 4 groups: the ones running in the low-mountain (<1000 m asl) zone, in the low (1000–1500) and upper (1500–2000) parts of the middle mountains and in the high-mountain (>2000 m asl) zone. A total of 71 EPT macroinvertebrate taxa were recorded in the studied streams. Species richness (according to the average species number per sample) as well as abundance and biomass of macroinvertebrates decreased with an increase in altitude. The maximum variance in structural indicators of communities appeared due to the combined influence of the location of the altitudinal zone and phytoplankton development level (estimated by the content of chlorophyll a). At the same time, categorical predictors (both abiotic and biotic) included in the analysis better explained the variability of diversity-related indicators than that of abundance and biomass. When developing the environmental monitoring programs for mountain watercourses, the identified trends in reduction (with altitude) of species richness of macroinvertebrate taxa responsible for the formation of taxonomically poor and strongly vulnerable communities in high-altitude areas should be taken into account.

The species composition, abundance and biomass, trophic relationships of phytoplankton and zooplankton, as well as the proportion of dead individuals in zooplankton were studied in the water system "Pregolya River – Kaliningrad Sea Channel (KSC) – Vistula Lagoon – Baltic Sea" in July, August and October 2021. In total 173 taxa of phytoplankton and 73 taxa of zooplankton were found during period of investigation. The maximal species diversity was observed in the summer period, in autumn it was decreasing. The maximum number of taxa for both phyto- and zooplankton was found in the Vistula Lagoon and in the KSC, the minimum – in the Baltic Sea. In summer the 3 communities in phytoplankton, 4 in zooplankton, in autumn – 3 communities in both phyto- and zooplankton were found. The plankton communities were confined to water areas with different salinity: The Pregolya River, the KSC and the Vistula Lagoon, the Baltic Sea. The dominant complex of species at the stations differed; species of a predominantly freshwater complex were noted in the Pregolya River, brackish-water species were found in the Vistula Lagoon, and a marine complex of species was identified at the stations of the sea strait and in the Baltic Sea. More abundant plankton communities both in summer and autumn were in the KSC and the Vistula Lagoon (phytoplankton biomass varied from 1.19 g/m³ to 11.89 g/m³; zooplankton biomass varied from 305 mg/m³ to 1801 mg/m³). In this area the most optimal conditions for the development of plankton were formed such as an increased nutrient content and maximum water heating. Plankton communities both in the Pregolya River and in the Baltic Sea in summer and autumn were less abundant (phytoplankton biomass varied from 0.16 g/m³ to 2.50 g/m³; zooplankton biomass varied from 34 mg/m³ to 468 mg/m³). The most intense trophic relationships in the plankton community in the summer in the Baltic Sea, optimal – in the KSC and in the Vistula Lagoon were formed. The proportion of dead individuals in the zooplankton of the studied system in both seasons was maximal in the areas, which had the critical salinity for hydrobionts and high turbulence conditions such as KSC, the Sea strait and at the exit from Sea strait.

The life of lakes in winter is still insufficiently studied. The purpose of this article is a comparative analysis of the quantitative development of planktonic and benthic communities and the abiotic conditions of their existence during the ice-covered period in two small (<1 km²) northern lakes that differ greatly in morphometry and the degree of water humification. A significant difference was revealed in the seasonal dynamics of plankton communities in the studied lakes. In a deeper lake with water uncolored by humus, the quantitative development of phytoplankton at the end of the ice-covered period was almost as significant as during the open-water period. It is necessary to note the rapidity of changes in under-ice phytoplankton in early spring: in April 2020, the content of chlorophyll a in water changed more than six times during a week. There was no mass development of phytoplankton under the ice in a shallow highly humified lake. The zooplankton of the studied lakes was characterized by the opposite trend. In the deep-water lake, the winter zooplankton was noticeably inferior to the summer one in terms of the level of quantitative development; in the shallow lake, a high biomass (~1 g/m²) of zooplankton was noted throughout the entire study period. The macrozoobenthos of lakes in winter, on the whole, retained the same high level of quantitative development as in the open-water period. Seasonal differences were local and were caused by the redistribution of bottom animals due to changes in the oxygen and, possibly, temperature regime of bottom waters. In particular, due to hypoxic-anoxic conditions at the end of the ice-covered period, benthic animals migrated from the profundal zone of the deep-water lake. After the ice melted and the near-bottom waters were saturated with oxygen, the profundal community quickly recovered. Thus, the quantitative development of biological communities in winter can vary greatly even in closely located lakes, in particular, it depends on the degree of humification of the water body. Given the high dynamism of phytoplankton in early spring, the assessment of the role of the under-ice period in the life of lakes, apparently, requires long-term research, including detailed observations at the end of ice-covered period.

The Petrozavodsk Bay of Lake Onego is characterized by favorable temperature, food and oxygen conditions for the functioning of relict crustaceans Monoporeia affinis (Lindström, 1855) population. The analysis of the size-age population structure was performed for this species for the first time. In 2018, the spring and autumn state of the M. affinis population differed. The contribution to the total number of young crustaceans with a body length of 1.5–2.0 mm and 2.1–3.0 mm in May and September was distinguished. The number of these two size groups changed inversely from May to September, which indicated the growth processes of juveniles. The total contribution of young crustaceans to the total population at different stations varied within 40–50% in May and 20–40% in September. Based on the analysis of size-frequency histograms and the method of principal components, two age cohorts of crustaceans with a body length of 3.1–7.0 mm (the first cohort, age 1 year) and 7.1–10.0 mm (the second cohort, age 2 years) were identified. The proportion of the first cohort in the total population of M. affinis was on average 12% in May and September. The proportion of the second cohort in May was on average 2%, and in September it increased to 8%. The data obtained are in good agreement with two age cohorts of M. affinis in other lakes of Karelia.

For the first time in Lake Onega, the reproduction features of the alien amphipod Gmelinoides fasciatus (Stebbing, 1899) were studied based on research in 2010–2011. The period of reproduction in the conditions of the reservoir (May–September) were established, the body length ranges of egg-bearing females, the average and maximum sizes of breeding individuals, as well as fertility were determined. During the study period, a decrease in the average size of females from May–June to August–September was noted, which is associated with the beginning of reproduction of females of the summer generation and the continued reproduction of females of the last year's generation. Equations were calculated that make it possible to predict the fecundity of females by body length, which indicates similar patterns of generative growth of G. fasciatus on the littoral in the northern bays of Lake Onega. Generally, the fecundity of the amphipod is higher in Lake Onega compared to the fecundity of the same species in Lake Ladoga, Neva Bay, Lake Arakhley and the Bratsk Reservoir. This phenomenon is probably associated with the geographical location of Lake Onega, a higher latitude and a longer photoperiod.

The initial prerequisites for the application of the parameters of the Bertalanffy growth equation for estimating the maximum age of fish life (t_λ) and the natural mortality rate (M) are analyzed. This approach has been proposed by D. Pauli and was widely used. Pauli found a regression dependence of the natural mortality rate on the parameters of the Bertalanffy growth equation (L_∝, K) and environmental temperature (T) for various populations on a large amount of factual material. However, the presence of a causal relationship between the growth rate and the natural mortality of fish has not been proven, therefore, it seems doubtful whether it is possible to solve the inverse task – determining mortality rate by growth parameters. A numerical example shows that in reality the values of the parameters of the growth equation can vary over a very wide range depending on the original data and do not correspond to their biological interpretation. Therefore, the growth cannot be used to estimate mortality. Since mortality is the rate at which fish decrease in number, this rate should be used for estimation of mortality.

The article provides an overview of all known 39 localities of the Paleogene turtles of Eastern Europe. Numerous remains of turtles are described for the first time from 19 localities, of which six are new, and 13 are the localities from which materials were only mentioned previously. Among them are Pan-Trionychidae indet., Pan-Cheloniidae indet., Dermochelyidae indet. and Pan-Testudines indet., as well as pan-cheloniids Argillochelys sp. from the Ypresian Novoivanovka and the Ypresian or Lutetian Gruzinov localities. Several indeterminate specimens from Eocene localities show similarity to pan-cheloniids Argillochelys cuneiceps (Owen, 1849) and Puppigerus camperi (Gray, 1831) or Tasbacka aldabergeni Nessov, 1987, and dermochelyids Natemys peruvianus Wood et al., 1996 or “Psephophorus” rupeliensis van Beneden, 1883. One specimen of costal 1 of Pan-Testudines indet. from the Lutetian Krasnorechenskoe locality resembles that of pleurodires Eocenochelus spp. and Neochelys spp. In addition, new materials of turtles are described from five previously known localities. Among them, new and additionally restored specimens from the Bartonian Ak-Kaya 1 locality of the pan-cheloniid Argillochelys sp., and the dermochelyid Cosmochelys sp., which expand data on their morphology and intraspecific variability. The specimens of pan-cheloniids with deep and dense sculpturing of the external shell surface from the Bakhmutovka, Bulgakovka, Krasnorechenskoe and Tripolye localities clearly belong to a new species, not described due to fragmentary material. It is supposed that Anhuichelys-like pan-testudinoids migrated from Asia in Eastern Europe in the Danian age, and were preserved as relict Dithyrosternon valdense Pictet et Humbert, 1855 until the Priabonian age.

The present paper is a preliminary attempt to develop a protocol for analyzing Late Pleistocene and Holocene paleocommunities of soricids using modern approaches for the morphological data analysis. First, we assessed the abilities of fossil soricid collections from Ural and Far East localities to provide a complex interregional analysis of the phenotype variation. Accordingly, for the first time in the general context, the study provides a species list and chronological position of Ural and Far East shrew fossil samples in terms of inter- and intraregional comparisons to reveal general and specific responses of paleocommunities to climatic fluctuations. Second, under the modern approaches, we prepared 182 three-dimensional models of hemimandibles or isolated m1 and built the morphospace of m1 shape for seven Sorex species from the Upper Pleistocene layer MKl-13 and Middle Holocene layer MKl-7 of Medvezhyi Klyk Cave (South Primorye, Russia). Recent samples from East Siberia (Yakutia) and the northern part of the Far East (Magadanskaya Oblast' and Khabarovsky Kray; “cold” habitats) and South Primorye (“warm” habitats) were included into morphospace to actualize potential responses of the fossil samples to Late Quaternary climate fluctuations. Our analysis revealed: (i) a weak reaction of m1 shape of almost all species to the “cold” and “warm” environmental conditions, except S. daphaenodon Thomas, 1907 and S. caecutiens Laxmann, 1788; (ii) two groups of species, namely “generalized” and “specialized” in m1 shape, in line with the idea of distribution of trophic niches among coexisted shrews; (iii) a diagnostic character for fossil samples of S. unguiculatus Dobson, 1890 and S. isodon Turov, 1924.

Prolecithophorans (Plathelminthes, Prolecithophora) stand out among the free-living flatworms (“turbellarians”) for a number of unique features of spermatozoa. The ultrastructure of male germ cells of two species of prolecithophorans from the Plagiostomidae family – Plagiostomum vittatum (Frey et Leuckart, 1847) from the White Sea and Vorticeros ijima Tozawa, 1918 from Inner Japanese Sea – was described. Spermatozoa of both species are characterized by an elongated fusiform shape, a spiral shape of the nucleus with an electron-dense fibrillar chromatin, the presence of numerous mitochondria that tend to merge, the cortical position of microtubules, and the absence of flagella. “Folded membrane derivatives”, specific for prolecithophorans, are present in mature spermatozoa of both species, but their morphology differs. They were not found in spermatids of Pl. vittatum. The nucleus of spermatozoon of Pl. vittatum is distinguished by the presence of numerous thin outgrowths. It has been suggested that the ultrastructural features of prolecithophoran spermatozoa (number and location of mitochondria, morphology and origin of “folded membrane derivatives”) can be applied in the phylogenetics of this group.

This paper analyzes the data of bird counts conducted in 1998–2021 in the province High-Mountainous Dagestan. For the first time, information was obtained on the modern average abundance of birds, their conservation status, residence status, species and faunistic composition. Of the 117 bird species recorded in the High-Mountain province of Dagestan, European, widespread, Mediterranean and Tibetan representatives of faunal complexes dominate in its humid northwestern and central parts, which is due to the prevalence of forests and shrubby subalpine meadows with large-scale rocky outcrops. In the southeastern, more aridized and treeless part of the highlands, where subalpine and alpine meadows with local rock inclusions dominate, representatives of the widespread, Mediterranean and Mongolian types of fauna are already taking the leading positions. Studies have shown that in mountains with a blurred altitudinal-belt gradient associated with the inversion of vegetation belts, the avifauna is subdivided not according to altitudinal differences, but according to habitats with corresponding ecological bird communities. Using the original ecological classification, the ecological structure of the avifauna of the study area was determined, including 11 ornithocomplexes differentiated according to the same type of habitats with an indication of their total abundance. Each habitat with the corresponding ornithocomplex was characterized according to ecological specifics, indicating with the indication of the first 5 species leading in terms of abundance. It has been established, that the specific appearance of the avifauna of the High-Mountinous Dagestan is given not only by the resident communities of typically mountain birds, but also by the adapted populations of migratory birds of the plains nesting in the highlands. The empirical data obtained make it possible to use them for spatial indication of bird communities for research purposes, for monitoring the state of the avifauna and its protection, as well as for organizing the rational use of hunting and commercial resources.

Acoustic playback techniques involve broadcasting of various sound stimuli to simulate the presence of a certain species. In this article, we applied a variation of the method using automatic sound-reproducing stations (ASRS), which imitate the daily vocal activity of birds that is close to natural. We investigated whether acoustic playback experiments help to examine the role of social cues for bird settlement decisions, as well as to detect the presence of rare and low-density species. Using this method, we were able to increase the local density of the rustic bunting Ocyris rusticus Pallas, 1776 (Emberizidae) – species, which is currently listed in the Red Book of the Russian Federation (2001). The findings of our study show that rustic buntings preferred to settle on plots where the song imitating the presence of conspecifics was broadcasted by ASRSs. In addition, the playback method was used to examine the social structure of the population of the wood warbler Phylloscopus sibilatrix Bechstein, 1793 (Sylviidae), a small species that lives here on the northern periphery of the range. The wood warbler songs were broadcasted by ASRSs before the arrivals of the first conspecifics to the breeding area. Songs with different acoustic activity (2 or 6 trills per min) were used to create a difference between the social environments on plots. The gathered data showed a display of two different behavioral responses of individuals (males) to different song types broadcasted on plots. Based on this observation, the main hypothesis is about the existence of both conservative and opportunistic male reproductive strategies of the wood warbler. The results demonstrate the possibility of using acoustic playback techniques to study the role of acoustic signals in territorial behavior and social structure of a bird population. Understanding the ways birds make settlement decisions is essential for the development of conservation practices.

The Early Pleistocene site of Palan-Tyukan (MNQ18, ca 1.85 Mya) is located in Transcaucasia, northwestern Azerbaijan. In total, more than 300 mammalian bones were collected there by one of the authors (M.V. Sablin) in 1986 and 1990. The remains were laid close to each other in a 25 m² lens-like accumulation, in a stratum of normally magnetized (the upper part of the Olduvai subchron) yellowish-grey Lower Apsheron loams. No any excavations have been carried here out since. The present study is based on the analysis of the Bovidae remains. The material is represented by fragments of skulls and horn cores, isolated teeth and bones of the postcranial skeleton. As a result of the revision of the collection, Leptobos (Smertiobos) cf. etruscus (Falconer, 1859), Gazellospira torticornis (Aymard, 1854) and Gazella cf. bouvrainae (Kostopoulos, 1996) were identified. The degree of the unworn M3 tooth hypsodonty of Leptobos, as well as the size and morphology of limb bones indicate a greater similarity with those of L. etruscus from Olivola and Tasso. The characteristics of the horn cores, as well as the upper teeth and limb bones of the medium-sized spiral-horned antelope from Palan-Tyukan indicate a greater similarity with those of the nominative subspecies G. torticornis torticornis. The dimensions and degree of flattening of the horn cores, as well as the parameters of the p4 tooth, are similar to those of the medium-sized gazelle G. bouvrainae, described from several Early Pleistocene localities of Greece. The taxonomic composition of the Bovidae association from Palan-Tyukan is consistent with the previously determined stratigraphic position of the locality, the fauna from which belongs to the Psekups faunal complex of Eastern Europe, correlated with the Late Villafranchian of Western Europe. The composition of these herbivores community testifies to the spread of savanna-like forest-steppe landscapes in the west of Transcaucasia during this period of the Early Pleistocene.

More than 1500 bones of the skull and postcranial skeleton of the Mongolian gazelle (Procapra cf. gutturosa Pallas, 1777) from 4 Paleolithic sites of Western Transbaikalia (Varvarina Gora, Kamenka, Khotyk, Tolbaga) and 3 cave localities of the northwestern Altai (Denisova, Strashnaya, Kaminnaya) were studied. For comparison, a large collection of skeletal bones from 56 individuals of modern P. gutturosa, collected on the territory of the “Dzeren Valley” nature reserve, was used. A number of morphometric differences in the structure of the lower jaw and bones of the postcranial skeleton between modern and fossil Mongolian gazelle have been revealed. Pleistocene P. cf. gutturosa had shorter and relatively massive limb bones and was significantly smaller in body size than the modern one. At the sites of Transbaikalia, Mongolian gazelle bones can account for up to half of all megafauna remains, in the Middle-Late Pleistocene layers of Altai caves, up to 3–4%. During the periods of glaciation, the Mongolian gazelles of Transbaikalia and Altai lived in conditions of cold, dry and little snow steppe or mountain-steppe landscapes. In the interglacial and interstadials, they continued to live here in the conditions of steppe or forest-steppe landscapes.

The paper presents the results of age and growth studying of the Tajikistan toadhead agama Phrynocephalus sogdianus by skeletochronology. A total of 29 adult individuals (14 females and 15 males) from the vicinity of Uchkyzil (Termez district, Surkhandarya region, Uzbekistan) were studied. All animals, on the section of tubular bones had a birth (hatching) line appearing shortly after the lizards hatching. The majority of the sample consisted of one-year-old and two-year-old specimens (89.7%). The age of females and males varied between 1–3 years, averaging 1.53 and 1.71 years, respectively. The expected calculated life expectancy for females after one wintering was 2.25 years, for males 2.06 years. Females and males did not differ in body length. The length of the males’ body depended on their age. Males aged one and two years statistically significantly differed in size among themselves. The authors note that P. sogdianus has very high growth rates (growth coefficient k is 2.84 in females and 1.40 in males), exceeding that of other toadhead agamas.

The article provides a brief biography of the ichthyologist Dmitry Nikolayevich Taliev (1908–1952), as well as information and illustrations for 24 taxa described by him from the White Sea (Gadidae – one subspecies), the coast of the Sea of Okhotsk (Salmonidae – one subspecies), Lake Baikal (Cottidae – 2 species and 4 subspecies; Abyssocottidae – 6 species and 8 subspecies), and Lake Baunt (Cottidae – 1 subspecies; Abyssocottidae – 1 species). For 19 taxa, photographs and radiographs of type specimens kept in the collection of the Zoological Institute of the Russian Academy of Sciences (Saint Petersburg, Russia) are presented for the first time. Type specimens of three species and two subspecies from the families Cottidae and Abyssocottidae found in the collection are examined and catalogued. It was revealed that Cottus kessleri bauntovi Taliev, 1946 and Limnocottus kozovi Taliev, 1946 are morphologically similar to Cottus sibiricus, a species widely distributed in Siberia, including Lake Baunt. According to modern fish taxonomy, Taliev’s 12 taxa are valid. Findings of type specimens in the historical collection are extremely important for the scientific community.

The external morphology and axial skeleton of 5 species of Antarctic plunderfishes of the genus Artedidraco Lönnberg, 1905 were studied using materials from the collection of ZIN. Plastic (26) and meristic (14) characters were analyzed; a morphological characteristics of the species was prepared. The results of the study partially con firm the previously revealed differences between the species of the genus, but some diagnostic characters of plunderfishes are found for the first time: the number of branched rays of the caudal fin, height of the head, length of the chin barbel and height of the second dorsal fin, predorsal, preanal and prebranchial distances, number of vertebrae in different parts of the spine. Assumptions are made about the functional role of characters, according to which the differences between the species associated with the diet and habitat of these fish are established. Two groups of Artedidraco species were found: “skottsbergi” (A. skottsbergi Lönnberg, 1905, A. loennbergi Roule, 1913) and “shackletoni” (A. shackletoni Waite, 1911, A. glareobarbatus Eastman et Eakin, 1999). Species of A. mirus Lönnberg, 1905 and A. orianae Regan, 1914 were not assigned to any group, since during the work a sufficient number of their similarities was not found. An identification key for species of the genus was compiled.

Two new species of benthopelagic calanoid copepod Bradfordian genera Pseudophaenna japonica sp. nov. and Xantharus dubius sp. nov. are described from collections of the Russian-German deep-sea expedition (SoJaBio) to the Sea of Japan onboard of the R/V Akademik Lavrentyev, 51st cruise taken close to the sea bed. The rare calanoid copepod genera Pseudophaenna Sars, 1902 and Xantharus Andronov, 1981 and a rare aetideid species Bradyidius rakuma (Zvereva, 1977) are recorded for the first time from the Japan Sea; the male of B. rakuma is described for the first time. Pseudophaenna japonica sp. nov. is the second species described for the genus Pseudophaenna and is distinguished by biramous rostrum, antennule ancestral segment XXII without seta, details of oral parts setation in females and in P5 structure in dimorphic males. Xantharus dubius sp. nov. is described from males and is distinguished from congeners in the antennule ancestral segments XXII and XXIII not comparatively small relative to the segment XXI and in the large and robust uniramous P5. In the collections of the expedition SoJaBio in 2010 from the Japan Sea the near-bottom benthopelgic fauna of Calanoida have been represented by these species only and they all belong to the calanoid superfamily Clausocalanoidea.

It is assumed that the species of the genera Boreochiton G.O. Sars, 1878 and Tonicella Carpenter, 1873 originated in the North Pacific Ocean. The first representatives of these genera apparently penetrated into the northern part of the Atlantic Ocean not earlier than the Pliocene. Fossil representatives from the Late Cenozoic deposits of Europe, belonging to the genus Tonicella, have a sculpture of a tegmentum closer to the species of the genus Lepidochitona Gray, 1821, which suggests their transfer to this genus.

This study examines the taxonomic structure and commonality of species composition of ascidians in the Arctic seas of Russia, where there are currently registered more than 70 representatives of this group. Quantitative analysis of taxa of different ranks inhabiting the study area demonstrates that their abundance decreases from west to east, and species composition in all seas, except Kara Sea, is understudied on average by 13±4%, and understudy increases in the eastern direction. The maximum decrease in the species composition in the mentioned direction is common for the families Polyclinidae and Didemnidae. The richest by number of species are genera Molgula Forbes, 1848 and Dendrodoa MacLeay, 1824. The performed clustering allows us to assume a predominant formation of regional ascidian faunas under the influence of the northeastern Atlantic. The results of finding multiple regression parameters confirm this hypothesis, which show that the actual and theoretically maximum number of species in Ascidiacea faunas of the Arctic seas of Russia depends only on the depth of water bodies and the length of their western and eastern borders (R²_adj = 0.814; p = 0.015).

Four new species of scale insects collected in Mexico are described and illustrated. Puto bicirculatus sp. nov. (Pseudococcidae) seems to be most similar with the widely distributed P. barberi (Cockerell, 1895), but differs from the last in the presence of 2 distinct circuli, in 15–16 pairs of cerarii (instead of 17–18), in more numerous tubular ducts (especially on abdominal sternites), and in very poorly developed ostioles. Acanthococcus reineri sp. nov. (Eriococcidae) has peculiar microtubular ducts with bifurcate opening and differs from congeners posessing the same type of wax glands in the fine structure of microtubular ducts, which have the duct, subdivided into 2 parts: thinner (connected with bifurcate opening) and distal larger part. Philephedra zipolitana sp. nov. (Coccidae) differs from all congeners in the fine structure of invaginated conical setae («dorsal tubercles»); these setae have truncate apex and surrounded each at the base by 5–6 oval pores; invaginated setae and pores are located inside of pot-like cuticular pouch, which is slightly narrowed at the orifice. Prionococcus alexandrae sp. nov. (Coccidae) differs from all congeners in the marginal setae (mainly bulbous), forming loose, widely interrupted row with gaps several times longer than setae and in the absence of stigmatic setae. The overlapped diagnostic characters of the nominal genera Philephedra Cockerell, 1898 and Alichtensia Cockerell, 1902 (Coccidae) are briefly discussed.

A new material on the Neotropical genera Lichenomorphus Cadena-Castaсeda, 2011, Dissonulichen Cadena-Castaсeda, 2011, Theia Brunner-Wattenwyl, 1891, Hetaira Brunner-Wattenwyl, 1891 and Anaulacomera Stål, 1873 (Phaneropterinae) are considered with description of one new subgenus, 16 new species and six new subspecies: Euceraicerca subgen. nov. from Anaulacomera s. l.; L. dietrichi sp. nov. from Panama (Chiriqui Prov.); L. piraniucayali subsp. nov. from Peru (Ucayali Department); D. roseola sp. nov. from Peru (Cusco Department); Th. (Theia) albamacula sp. nov. from Peru (Cusco Department); Th. (Th.) sergeii sp. nov. from Peru (Cusco Department); H. (Hetaira) miaria sp. nov. from Peru (Cusco Department); A. (Cervicercora) tshugaevae sp. nov. from Peru (Cusco Department); A. (C.) lehnfeldae sp. nov. from Peru (Cusco Department); A. (C.) cristalica sp. nov. from Peru (Junin Department); A. (C.) rectiapex cusco subsp. nov. from Peru (Cusco Department); A. (C.) abrupta sp. nov. from Peru (Cusco Department); A. (C.) a. neglecta subsp. nov. from Peru (Junin Department); A. (C.) superapex hamata subsp. nov. from Peru (Cusco Department); A. (C.) lativenosa sp. nov. from Peru (Loreto Department); A. (C.) l. serrata subsp. nov. from Peru (Junin and Cusco Departments); A. (C.) angustissima sp. nov. from Peru (Cusco Department); A. (C.) rotundiloba sp. nov. from Peru (Cusco Department); A. (C.) abbreviata urubamba subsp. nov. from Peru (Cusco Department); A. (Oecella) panama sp. nov. from Panama (Panama Prov.); A. (Oe.?) leonidi sp. nov. from Peru (Junin and Cusco Departments); A. (?) minicercata sp. nov. from Peru (Cusco Department); A. (?) viadanocerca sp. nov. from Peru (Cusco and Junin Departments). Previously unknown female and male of H. (Atopana) morona Gorochov, 2014 and H. (H.) angusta Gorochov, 2014, respectively, are described. Some new data on geographical distribution of a few species are also given.

The study of interannual changes in the structure of soft soil macrobenthic communities was carried out on the basis of material collected in three littoral sites in the waters of the Keret archipelago of the White Sea in 1983– 2013. The analyzed sites differed in biotopic heterogeneity (characteristics of the soil, degree of closure of water areas, salinity regime). This is a sandy beach in a seaward zone, and two silt-sandy beaches in a semi-enclosed and practically closed water area. The latter is located near the mouth of the Keret River, and is also under the influence of lake runoff, respectively, experiencing a slight freshening. The distance between the sites does not exceed a few kilometers. At two sites, significant changes in the structure of macrobenthos were noted, up to a change in the species dominating in biomass. The study of conjugation of fluctuations in abundance and biomass of common species showed that most taxa demonstrate an independent change in abundance indicators. However, in areas where sea grasses dominated in biomass, the change in the number of significant correlations between taxa, both in abundance and biomass, in some years occurred in accordance with fluctuations in the biomass of Zostera marina Linnaeus, 1753. It was not possible to find climatic and hydrological indicators that would explain the interannual changes in macrobenthos abundance indicators at once in all sites, despite their slight distance from each other. Thus, the conducted studies showed that the structure of macrobenthos of soft soils in the dry zone and the upper sublittoral in the region of the Keret archipelago was distinguished by spatial and temporal heterogeneity, in which one can see a reflection of the biotopic heterogeneity of habitats, features of interspecific relationships, and dynamics of the structure of settlements of dominant species. Under relatively stable climatic, hydrological, and edaphic conditions, significant changes in the structure of the White Sea littoral bottom communities of soft bottoms were mainly determined by natural changes in the structure of settlements of dominant taxa.

Cryptic mussel species Mytilus edulis (Me) and M.trossulus (Mt) form mixed settlements in shallow waters of the White Sea. The proportion of Mt and Me in local settlements varies in broad limits but the factors regulating taxonomic composition of mixed populations are poorly understood. Present study focuses on the assessment of the sea star (Asterias rubens) predation influence on the Mt-Me ratio in natural habitats. For this purpose, we’ve conducted a series of field experiments. For mussels placed on experimental units (ceramic plates submerged in starfish-infested habitats), we’ve estimated a probability of being eaten by starfish. We’ve constructed a linear model that includes several predictors which may influence the probability of being eaten (starfish biomass, mussel size, mussel species, prey abundance, Mt-Me ratio on experimental units and abundance of conspecifics). The analysis has revealed that the probability of being eaten expectedly increases with sea stars’ biomass increasing, but it is higher for Mt in comparison with Me. This indicates Mt as a preferable prey. Negative correlations between the probability of being eaten and shell size, number of conspecifics and mussel abundance were also revealed. No significant dependence on Mt-Me ratio was found. Additionally, we’ve taken field samples which revealed a significant decrease in the proportion of Mt in mussel patches after a massive starfish attack. This indicates that starfish ate out Mt as its preferable prey. These results show that predators can contribute to the regulation of taxonomic composition of mixed Mt-Me settlements in the White Sea.

As a result of studying the populations of Eurytemora genus crustaceans from the internal reservoirs of the drainage basin of the White, Pechora Seas, the Lena deltas, Island of Wrangel and Kamchatka peninsula was set that the species Eurytemora gracilicauda is common along the entire northern border of Russian Eurasia. It was shown that the species distribution for populations from the rockpools of the Kandalaksha Bay of the White Sea, from Lake on Kashin Island in the Pechora Sea and from the Lena River Delta was sequentially along the coast of the Arctic. Studies are based on genetic (parts of CO1 and ITS1 genes) and morphological analyzes of the studied populations. The synonymy of the Kamchatka species E. kurenkovi and E. gracilicauda was confirmed by the morphological analysis. Variation coefficients (CV), calculated for the populations of females from the White Sea, the Lena River delta and from the Kamchatka do not exceed 10%, which indicates a low morphological variability of the species. The most widely represented in the genetic analysis, the White Sea population has a low level of genetic variability, which, together with significant tolerance to the fluctuations of salinity in the rockpools in which it lives, may indicate its recent introduction to the region. A phylogenetic reconstruction was not revealed reliable topology for the species E. gracilicauda. It was shown that E. gracilicauda is not related to the affinis group species. Molecular Clocks with use part of CO1 gene and paleontological calibration revealed the speciation of E. gracilicauda species on the Paleocene – Late Cretaceous boundary. We also can hypothesize a Laurasian origin of the Eurytemora genus.

The composition of the nemertean fauna of the White Sea is summarized from the literature, collections of the Zoological Institute of the Russian Academy of Sciences and our own samples. According to published data, 52 species have been recorded for the White Sea. One of them (Tertastemma laminariae Uschakov, 1928) is recorded mistakenly, records of another six species (Cerebratulus pantherinus Hubrecht, 1879; C. fuscoides Bürger, 1892; Micrura albida Verrill, 1879; Amphiporus bioculatus McIntosh, 1874, Tetrastemma flavidum Ehrenberg, 1828 and “Tetrastemma” vittigerum (Bürger, 1904)) should be considered doubtful for the White Sea. Currently, the fauna of the White Sea nemerteans includes 43 species from three classes, five orders and 12 families. From them, five species are not formally described yet, six species identified only to the genus level, and seven species are nomina dubia. Due to the lack of a regional guide for species identification, keys are proposed for 17 common species of White Sea based on external morphology. These keys can be used during student practices and hydrobiological studies. Mass species in the littoral of the White Sea are Lineus ruber (Müller, 1774), L. viridis (Müller,1774), Amphiporus lactifloreus (Johnston, 1828) and Cephalothrix filiformis (Johnston, 1828). Arctostemma arcticum (Uschakov, 1926) is a very common one in the upper muddy subtidal zone up to 7–9 m, where Cephalothrix spp. and Micrura sp. are also not rare. Gurjanovella littoralis Uschakov, 1926, Micrura spp. and Cerebratulus filiformis live in deeper water. The nemertean fauna of the Kandalaksha Bay is the most studied, where 33 species are registered. The greatest contribution to the study of the White Sea nemertean fauna was made by P.V. Uschakov, V.S. Korotkevitsch, A.V. Chernyshev, and S.A. Maslakova.

In connection with climate warming in recent years, it has been reported about the "borealization" or "atlantization" of the Barents Sea region. Along with other manifestations of this process, heat-loving migrants, which are not typical for these waters, are increasingly being observed in the Barents Sea. Thus, whiting Merlangius merlangus (Linnaeus, 1758) began to occasionally occur along the coast of Murman, the main range of which is in the North Sea. The article presents data on the captures of whiting in the White Sea, where this species was not previously known. The specimens were caught in September 2013 and in August 2017 in the Kandalaksha Bay (Chupa Bay near the Cape Kartezh, area of the biological station of the Zoological Institute of the Russian Academy of Sciences, ca. 66°20.23’N; 33°38.97’E). The characters that distinguish it from other codfish species of the White Sea are listed; information is given about its rare captures in the Barents Sea region. Naturalization of whiting in these waters, apparently, does not occur; for it, this marginal area of the range is a zone of sterile expatriation.

The paper investigates the possibility of determining the age of dub Limanda limanda Linnaeus, 1758, by the length, width, thickness and mass of the otolith. The purpose of the study is to evaluate the possibility of using this method. A total of 247 otoliths (172 females and 75 males) were processed. The age of the dub in the Chupa Bay ranged from 2 to 12 years, while the sample was based on individuals 3–6 years old (81.8%). The average values of the otolith parameters for each age class are given. The dependences between age and otolith parameters are expressed by a logarithmic function. Regression equations describing the relationship between the age of an individual and the parameters of the otolith of the dub were calculated, and a correlation between these indicators was noted. The calculated correlation coefficients of the dependence of the age of the fish on the otolithometry parameters showed that the highest values of the coefficients were revealed by the dependencies "age of the fish – mass of the otolith" and "age of the fish – thickness of the otolith". It was found that the same-aged females have large values of the length and mass of the otolith compared to males. It is recommended to use the otolith mass as an express method for determining the age of the dub. There are no similar works on the dub in the scientific literature.

The present paper is a synthesis of all the results of long-term (for almost 35 years) observations of beds of nine widespread bivalve species, carried out at the Marine Biological Station of St. Petersburg State University in the White Sea (Chupa Inlet mouth, Kandalaksha Bay). The purpose of the investigations is to identify the patterns of the spatial-temporal organization of bivalve beds. As a result, a generalized analysis of the reasons for the spatial and temporal heterogeneity of the bed structure of widespread long-lived bivalve species in an undisturbed environment is presented, and attempts are made to develop models of the dynamics of the age structure of bivalve beds in the White Sea. An integrated approach to identifying the patterns in the organization of bivalve beds: the study of changes in the size-age structure of beds as a reflection of the recruitment, growth and mortality features, made it possible to identify intraspecific relationships as determining long-term trends in the structure changes of mollusk beds in the White Sea. Studies have shown that long-term stability of size-age structure is not a typical feature of the bivalve beds in the White Sea, and substantial fluctuations in their structure take place even under relatively undisturbed environmental conditions. The main reasons for the fluctuations of the bed structure appear to be connected to inter-annual variation in recruitment rates. These variations are mainly caused by the intensity of mollusks intraspecific interactions, and by the conditions of mollusk survival in the early stages of the life cycle. As a result of interannual fluctuations in the bed bivalve recruitment rates, specimens of only 1 or 2 generations dominated for several years. A periodic change of the dominant generations could be considered as a recurrence in the bed development. However, the recurrence of the bed structure dynamics can be easily disrupted under unfavorable conditions for the mollusk survival in the early stages of the life cycle. The bivalve stationary beds in the White Sea are likely the exception from the general rule. They can be formed in case of a relatively stable level of annual recruitment with a decrease in intensity of intraspecific competition. The latter in the White Sea beds of Bivalvia was observed either when the ecological needs of individuals of different ages were differentiated, or in the case of a relatively poor bed density.

The life cycle of P. pungitius (Linnaeus, 1758) includes migrations from the open sea to coastal and freshwater biotopes which are accompanied by osmotic shock and following oxidative stress in fish. The complex multilevel antioxidant system (AOS) includes low-molecular compounds and specific enzymes and protects cells from reactive oxygen species, hydrogen peroxide, and hydroperoxides generated in excess. To study the response of AOS components to oxidative stress caused by acute salinity changes, nine-spined stickleback juveniles from the White Sea estuary were alternately exposed to hypo- and hyperosmotic conditions.  In the tissues of stickleback transferred from saltwater to freshwater for 1 and 24 hours a decrease in water-soluble protein concentration and catalase activity was shown. The increased guaiacol-dependent peroxidase activity in estuary fish successively exposed to fresh and saltwater for 24 hours was also observed. Under studied exposures, no changes in the activities of superoxide dismutase and glutathione S-transferase were detected. The involvement of AOS enzymes, particularly neutralizing hydrogen peroxide by the peroxidase-dependent pathway, in the response to acute changes in ambient salinity was described in White sea P. pungitius for the first time. The results of our study provide the new data on the AOS response to hypo- and hyperosmotic stress in euryhaline fish species. The obtained data could be used in predicting the possibility of industrial fish farming in the White Sea-Barents basin.

Using trapping and ringing of birds for studying the ecology and the demographic parameters of populations is necessary to determine as accurately as possible in which period of the annual cycle each individual was caught. The first-year passerine birds undergo juvenile migration (usually in form of postfledging dispersal) and postmoulting (autumn) migration in summer-autumn period. These stages of annual cycle are difficult to identify in trapping birds by calendar dates because the timing of migration seasons can significantly overlap in the same location. The study of moult at the Ladoga Ornithological Station made it possible to determine the states of plumage that mark juvenile and postmoulting migrations in first-year birds. The article presents two examples of the use of moult progress in the study of bird migrations. The first one is an analysis of the ratio of the terms of departure and passage in three long-distant and three short-distant migrants of passerines. It has been shown that the timing of the departure of local birds is earlier than the timing of the passage of other populations in all studied species, while the last local individuals in long-distance migrants are recorded long before the end of the passage of the species, and in short-distance migrants they can be found until its end. As another example, an analysis of long-term trends in the timing of summer-autumn movements in the Garden Warbler was performed. It is shown that for almost a fifty-year observation period, neither the timing of juvenile migration nor the timing of postmoulting migration of first-year birds has changed. At the same time, the timing of the spring passage of the species shifted to earlier. As a result, the duration of stay of the Garden Warbler in the Ladoga region has increased.

Pacific rainbow smelt Osmerus dentex Steindachner et Kner, 1870 is ubiquitous in the coastal areas of the White Sea, found mainly in desalinated bays. This is a semi-anadromous pelagic species. The paper presents biological data on the Pacific rainbow smelt from the estuarine part of the Nyukhcha River, collected in the period from 2004 to 2018. In the study area, its maximum length (according to Smitt) is 35.3 cm, weight is 398 g, the maximum recorded age is 10 years. It reaches maturity at the age of three years, less often in the second year of life. Spawning occurs mainly in May, less often in late April and early June. Eggs are laid on the bottom; average absolute fertility is 46.5 thousand eggs. It feeds mainly on crustaceans and small fish.

The intraspecific variability of the type species of the genus Incisiochiton is discussed and a new species of this genus from Paleocene deposits of Ukraine is described. The new species differs from the type species of the genus by the presence of oval pustules near the jugum and strongly curved ribs in the central area.