Abstract This paper presents the results of an analysis of karyotypes of larvae of Chironomus plumosus L., 1758 from the Rybinsk Reservoir collected in 2016–2019. Fourteen sequences of discs of polytene chromosomes have been revealed in 367 individuals. The karyofund of the studied population has been enriched with 23 new genomic combinations and includes 136 combinations for 1013 individuals throughout

Abstract The life cycle of the nematode Cosmocerca ornata (Dujardin, 1845)—a parasite of amphibians—was studied for the first time. The experimental infection of yearlings of the marsh frog Pelophylax ridibundus infected by larvae of C. ornata was performed. The development stages of parasites in the host were studied. It has been revealed that amphibians are infected with infectious larvae (J3) of

Abstract This paper presents general characteristics of the ichthyofauna of the Pechora River basin. Based on the results of ichthyological surveys in 1994–2018, as well as published and archived data, the current composition of the fish fauna, including the invasive species, is presented. The species diversity and taxonomic status of fishes and their place in various faunistic complexes are also considered

Abstract Data on the taxonomic composition of freshwater sponges and bryozoans in the cooling pond of CHPP-1 (Tyumen), as well as data on their distribution in the water area at five stations in 2005, 2016, and 2017, are given. The seasonal development of colonial invertebrates, as well as the influence of high temperatures on the occurrence and biomass of sponges, are considered. It is shown that

Abstract The results of field and experimental microbiological studies of water, soil, and rock samples in the influence zone of large landslide are presented. The landslide occurred in December 2018 and blocked the Bureya Reservoir from coast to coast. An artificial channel was created to restore the hydrological regime with the use of TNT (trinitrotoluene) and RDX (hexogen). A comparative analysis

Abstract The distribution of alien species of suckermouth armored catfishes (Loricariidae) in the water bodies and water streams of southern Vietnam has been studied. The taxonomic composition of suckermouth armored catfish is determined based on the data of morphological and molecular genetic analysis. Two species of armored catfishes, Pterygoplichthys pardalis and P. disjunctivus, as well as their

Abstract The long-term (postponed) consequences of the separate and combined effects of Cu2+ ions (0.001, 0.01, and 0.1 mg/L) and a low-frequency electromagnetic field (50 Hz, 10 μT) on roach Rutilus rutilus (L.) embryos have been studied, bringing to light the exposure to these factors to changes in the size and weight parameters, the activity of glycosidases (sucrase, maltase, and amylolytic activity)

Abstract Experience in using the integral index of the leukocyte structure to analyze the response of the fish immune system to various stress factors is summarized. This study yields new information on the nature of the response of the cellular component of the fish immune system to the effects of phenol, naphthalene, heavy metal salts, dichlorvos, an analog of cortisone, and ligulosis. The proposed

Abstract A total of 131 taxa of species and intraspecies rank of diatom algae from 41 genera have been identified during a scanning electron microscopy study of material from several rock pools on islands and the shore of the Kandalaksha Gulf in the White Sea. Among them, one species (Cymbopleura cf. angustata var. fontinalis Krammer) is new for the flora of Russia; 16 forms from 12 genera are identified

Abstract Data on trematode life cycles, fish host distribution, transmission, and fish and snail infection are reported in this review. European freshwater trematodes of the genus Sanguinicola (Aporocotylidae) remain an insufficiently studied group of trematodes. Five species of Aporocotylidae (Sanguinicola armata, S. inermis, S. intermedia, S. volgensis, and S. rutili) in freshwater fish of Europe

Abstract An illustrated description of two nematode species (D. lutosum sp. n. and D. stagnalis sp. n.) of the genus Daptonema Cobb, 1920, found in artificial reservoirs for shrimp farming in Vietnam and new to science, is provided. D. lutosum sp. n. is similar to D. borealis Gagarin, 2020 and D. dihystera Gagarin, Nguyen Vu Thanh, 2005 in the structure of the specular apparatus and body sizes. It

An Erratum to this paper has been published: https://doi.org/10.1134/S1995082921330014

Abstract We investigated the distribution of mitochondrial lineages of two species—the common roach Rutilus rutilus and Ponto-Caspian roach R. lacustris—in the broadest zone of their secondary contact, the Volga basin. For the purpose of species identification, we applied the approach of multiplex PCR based on species-specific divergences in sequences of the first subunit of cytochrome oxidase (COI)

Abstract The physiological mechanism of the long-term survival of dinoflagellates under a biogenic limitation has been studied using the cultures of three common species from the Black Sea—Prorocentrum cordatum, Prorocentrum micans, and Gyrodinium fissum—as an example. The transfer of P. cordatum and G. fissum cells, which have a maximum intracellular pool of nutrients, to seawater depleted in nutrients

Abstract Fish distribution in bodies of water is determined by a complex of abiotic and biotic environmental factors, most of which universally affect the distribution of fish, both in lentic and lotic ecosystems. At the same time, only some external factors, primarily the current and, in some cases, the temperature, are specific to particular types of water bodies. Fish distribution is a dynamic process;

Abstract The mass of pharyngeal teeth (pharyngeal jaws with teeth located on them) and its proportion of the total body mass of the roach Rutilus rutilus (Linnaeus, 1758) with different feed types in the Rybinsk Reservoir have been analyzed. It is ascertained that the proportion of pharyngeal tooth mass tends to increase significantly as the fish body length increases from 170 to 200 mm, body mass

Abstract Five species belonging to Lemnaceae family are known to grow in Siberia: Lemna gibba, L. minor, L. trisulca, L. turionifera, and Spirodela polyrhiza. Characteristics of their distribution in Siberia, bioecological characteristics, and facts of flowering and fruiting of Lemnaceae are provided in this paper. It has been shown that the generative reproduction of duckweed is not a rare phenomenon

Abstract Phytoplankton composition, development, and distribution, as well as hydrooptical characteristics, were studied in mesotrophic drainless Lake Krasilovskoe (Altai krai, Russia) in March and August 2017, and February 2018. Phytoplankton comprised 147 taxa with a rank below genus. In winter, the phytoplankton abundance was 0.03–1.06 × 106 cells/L, biomass 0.2–12.2 g/m3, and Chl a content 1.8–24

Abstract Visual observations performed by members of the International Public Organization Association of Underwater Activities of Crimea and Sevastopol have allowed for obtaining the abundance characteristics of brown meagre (Sciaena umbra Linnaeus, 1758) in the Crimean Black Sea waters. There have been 290 observations completed with an average duration of 4 h each and 64 fish specimens examined

Abstract This study analyzes the histological peculiarities of the internal organs of the lake form of Mongolian grayling Thymallus brevirostris (Kessler, 1879) caught in the cold-water mountain Lake Hindiktig-Khol (Tuva Republic, Russia) in the summer. The maturation of the females starts at 4+ years; the peak of their spawning activity is observed at 5+. Males mature 1 year earlier than females.

Abstract Diatoms from small waterbodies of polygonal microrelief tundra on Tit-Ary Island (the lower reaches of the Lena River) have been studied using scanning electron microscopy (SEM) for the first time. A total of 160 taxa belonging to 48 genera, 25 families, 13 orders, and 3 classes—including 55 taxa new for the flora of the Lena river basin, 46 taxa new for Yakutia, and 13 taxa identified only

Abstract The size–age structure and growth of the Sardine Cisco Coregonus sardinella, the Siberian Whitefish C. lavaretus pidschian, and the Broad Whitefish C. nasus in Lake Ioni in eastern Chukotka has been studied for the first time. According to the results, the linear growth rate in whitefish decreases with age. The maximum body-length increase was recorded in the first year of life. The linear

Abstract New faunistic data for 33 caddisfly species are reported in southeastern Belarus. Six caddisfly species are new for this region: Lupe phaeopa, Ceraclea fulva, Parasetodes respersellus, Anabolia laevis, Limnephilus fuscicornis, and Oligostomis reticulata. The location, distribution, and ecological–faunistic characteristics are given for each species found.

Abstract The effect of phenol (Ph, 0.25 mmol/L) on the activity and temperature dependence of casein- and hemoglobin-lytic peptidases functioning in the whole organism of chironomid larvae Chironomus sp. within the temperature range of 0−70°С at different рН values (3.0, 5.0, and 7.4) is studied. The temperature optimum of the studied peptidases of chironomid larvae corresponds to 40°С. Under the influence

Abstract New data on the content of chlorophyll a with pheopigments (Chl + Ph) in bottom sediments (BSs) of the Ivankovo and Uglich reservoirs of the Upper Volga (Russia) obtained in 2019 are given. The relationships between pigment concentrations and characteristics of bottom sediments and depth are analyzed. It is established that at present the average concentration of Chl + Ph is 156 μg/g dry weight

Abstract It is shown that increasing fish biomass due to planktivorous whitefish Coregonus lavaretus L. in Lake Sevan leads to a reduction in the number of species, abundance, and biomass of spring ZP. In addition, quantitative characteristics of large species of Cladocera, Daphnia (Ctenodaphnia) magna Straus, and a decrease in the Shannon index value are changing as well. A decrease in the number

Abstract A new finding of Thermocyclops taihokuensis (Harada, 1931) in European Russia is described. In October 2019, the East Asian copepod T. taihokuensis (Harada, 1931) was first recorded in the Shat Reservoir (54° N, 38° E) of the Oka River system. The Oka River is the right-bank tributary to the Volga River. The population of T. taihokuensis exceeded 100 000 ind./m3. The species actively reproduced

Abstract The results emphasise the significance of further studies in the Dir Lower to get well understanding of the helminth parasites with ecological relations of their hosts. Twenty-seven specimens of Bufo stomaticus (Lutken, 1864) (Anura: Bufonidae) were collected in the Dir Lower, Khyber Pakhtunkhwa province of Pakistan in the period from April to August 2016, and examined for helminths (endoparasites)

Abstract The results of an analysis of the taxonomic and typological structure of the flora in small reservoirs of the Vychegda River basin (Komi Republic) are presented. It is found that the composition of the combined flora of the reservoirs includes 160 species and hybrids (including 28 species of bryophytes and 3 species of charophyte algae). In the presence of common features, the flora of each

Abstract The effect of heavy-metal ions (Cd2+, Cr6+, and Cu2+) on cyanobacteria sp. Microcystis and sp. Synechocystis has been studied. Since heavy metals impact causes blocking of light-energy transmission channels and arrest of electron transport in photosynthetic apparatus of cyanobacteria, their influence can be detected within a few hours by fluorescence techniques. In this investigation three

Abstract A comparative study of the nutrition of climbing perch Anabas testudineus (Bloch, 1792)–fed with granular food with positive buoyancy in the light (~100 lux), in darkness, and under infrared light (780–900 nm) has been performed. It is found that climbing perch can eat equally as well in darkness and under infrared light (37 and 30% of the feeding granules), albeit much worse than in the light

Abstract Data on secretory glycoproteins (ependymins (Epd)), the main protein constituents of the cerebrospinal fluid (CSF) in teleost fish, are analyzed and summarized. In addition to the well-known functions of proteins (involvement in the processes of learning, memory consolidation, and nervous-tissue regeneration), data on the new functions of Epd that have been obtained in recent decades (involvement

Abstract Typical characteristics of the behavioral reactions of the Mediterranean mussel Mytilus galloprovicialis Lam, 1819 in its natural habitat of the Black Sea have been investigated using the originally developed automated biomonitoring complex of the aquatic environment. The valve movements exhibit a pronounced, clear solar diurnal rhythm, with maximum valve opening amplitude at night and minimum

Abstract Illustrated descriptions of two new free-living nematodes found in the Cấm River mouth in Vietnam are given. Eumonhystera rivalis sp. n. is morphologically similar to E. dispar (Bastian, 1865); E. sudanensis Zeidan et al., 1989; and E. maxima Gagarin, 1996, but differs by the presence of biocrystal-like bodies, amphid fovea located closer to anterior body end, and longer cephalic setae. Daptonema

Abstract Data on the species composition and dominant complex of turbellarian worms in the Ivankovo Reservoir in 2000, 2016, and 2017 are presented. Features of their distribution in the reservoir are considered. Temporal changes in qualitative and quantitative characteristics of the Turbellarian fauna have been found.

Abstract The dynamics of physiological and biochemical parameters of blood and urine in the process of gonad maturation in females of the sterlet × beluga hybrid (Acipenser ruthenus L., 1758 × Huso huso L., 1758) grown using CWSI technology is studied. It is shown that, when this technology is applied, features in functional changes that accompany the gonadogenesis of female hybrids appear, distinguishing

Abstract Water caltrop Trapa natans L. is a relic aquatic plant protected in 36 regions of Russia. The most northern and isolated populations of this plant in Southern Ural and Altai are poorly studied. The results of a chemical analysis of water and aquarium culture experiments revealed that this plant could tolerate a wide range of environmental factors. The species appear to be sensitive to chlorides

Abstract The content of Chl a and nutrients in the Upper Volga reservoirs in the summer of 2015–2018 has been studied. With Chl a content typical of the summer phytoplankton maximum (from 19.9 ± 3.9 to 48.0 ± 12.0 μg/L), the reservoirs are classified as eutrophic; the Rybinsk Reservoir was classified as mesotrophic only in cool 2017 (10.3 ± 4.7 μg/L). The content of nutrients (from 0.71 ± 0.06 to 1

Abstract The number of circuli between annual scale rings of grayling Thymallus baicalensis Dybowski, 1874 sampled in the Yenisei River in the downstream section of the Krasnoyarsk Hydroelectric Power Station, which does not freeze in winter, have been investigated and compared with populations of grayling from large tributaries of the Yenisei River (Amyl, Kan, Nizhnyaya Tunguska, and Bolshaya Kheta)

Abstract Data on the functional aspects of the effect of more than 25 types of anesthetic chemicals and physical factors on teleostean fishes are generalized. It is shown that most of the narcotic agents have a pronounced stress effect on the fish and radically change the fish state. Many of these agents cause a functional response at the level of separate physiological systems (respiration, blood

Abstract We assessed the efficiency of the transfer of essential substances (carbon, phosphorus, nitrogen, and fatty acids (FA), including polyunsaturated fatty acids (PUFAs)) from phytoplankton to planktonic crustaceans in experimental mesocosms in the presence and absence of fish. The experiments were conducted under mesotrophic conditions in 300 L mesocosms. We have found that transfer efficiencies

Abstract The results of a comparative and morphological analysis of pistillate flowers of Typha pontica from four water bodies in the south of Russia are presented. The typical morphological features of pistillate flowers of the species are established. Differences have been found in the structure of the pistillate flower of T. pontica during the formation of the surface of the pistillate part of the

Abstract Nupela giluwensis Vyverman & Compére 1991 has been found in the aquatic ecosystem of Vietnam for the first time. The main qualitative (valve shape, shape of valve ends, and morphology of striae) and quantitative (length, breadth, and striae density) data are studied. A comparison of the valves of the Vietnamese population and typical population show their morphological and ultrastructural

Abstract The micromophology of relict hydrophytes Brasenia schreberi J. F. Gmel. (Cabombaceae), Nuphar japonica DC. (Nymphaeaceae), and Nelumbo komarovii Grossh. (Nelumbonaceae) has been studied based on material from the Lower Amur region. Detailed descriptions of the anatomical structure of leaves in contact with the air are given. A common feature was the dorsoventrality of the leaf blade and the

Abstract Changes in the composition of reserve and membrane lipids in the gills of freshwater mussel Anodonta cygnea L., 1758 in response to the effect of copper at different concentrations (5, 50, 100, and 250 μg/L) are studied. Modifications in the content of phospholipids and their fatty acids depended on the duration of the copper effect: the unsaturation of phospholipids fatty acids increased

Abstract The seasonal dynamics of the motivational component of rheoreaction (ratio of rheoreaction types) has been studied in roach Rutilus rutilus L. inhabiting the Rybinsk Reservoir, Russia. The circular hydrodynamic tank with limnozone is used. The change in the ratio of rheoreaction types in nonmigratory mature roach may adequately reflect its behavior in the reservoir. The fish sex, stage of

Abstract The results of long-term determinations of the abundance, biomass, and production of heterotrophic bacterioplankton in the eutrophic Gorky Reservoir (Middle Volga) are discussed. The mean values of the parameters increased 1.7–1.9 times in 2015–2016 when compared to 1991–1999. During the entire period of studies, the maximum values were recorded in the abnormally hot summer of 2010, when the

Abstract The data on chlorophyll content in the water and bottom sediments in freshwater Rybinsk Reservoir (Upper Volga) and Aniva Sea Bay (Sea of Okhotsk) are summarized. The average concentration of chlorophyll a in plankton of the reservoir is 23.0 ± 1.9 μg/L, in the bay 0.77 ± 0.06 μg/L, in the bottom sediments 144.2 ± 14.9, and 8.2 ± 0.7 μg/g in the dry sediment, respectively. Correlations between

Abstract The content of mercury in adult water beetles is studied in beaver ponds located in the Polist-Lovat Swamp System (Novgorod oblast). A total of 201 individuals of nine species of the family Dytiscidae and one species of the family Hydrophilidae (size classes II and III) are studied. It is revealed that the mercury content in beetles of size class II differs significantly between species (χ2

Abstract According to the data of scanning electron microscopy, in the plankton of the shallow-water eutrophic waterbody of the Ptichiya Gavan natural park (Omsk), located in the South of Western Siberia, 105 morphotypes of stomatocysts of Chrysophyceae have been identified and combined into 20 groups. The variety of morphotypes is significantly higher than the abundance of Chrysophyceae species (24

Abstract Data on exogenous feeding in the early life stages of sturgeon in the wild and in aquaculture are analyzed. The data on food composition and feeding habits in sturgeon larvae at the stage of transition to exogenous feeding and some later in the wild are conflictive. Some data demonstrate that larvae, upon their transition to exogenous feeding, feed on zoobenthos; other data show that larvae

Abstract This review is devoted to analyzing the global occurrence of cyanobacteria in water ecosystems, the possible causes of this phenomenon, and its consequences. In recent decades, cyanobacteria have been rapidly expanding in waterbodies all over the world. This expansion is accompanied by water pollution with dangerous cyanotoxin metabolites that represents a significant threat to humans, animals

Abstract At the beginning of the dry season, immediately after the end of the rainy season, estimations of zooplankton abundance have been carried out in three types of shore areas of Lake Tana (Ethiopia): (1) open water, (2) borders of thickets, and (3) macrophyte thickets. The minimum quantitative characteristics of plankton animals are reported in macrophyte thickets; the maximum are in areas of

Abstract An analysis of published data and data of our own on the features of using biomarkers of oxidative stress in bivalve mollusks for ecotoxicological studies of fresh waters is presented. Various protective mechanisms of the antioxidant system in Bivalvia in response to the action of organic contaminants and heavy metals are described. Several examples of the use of bivalve mollusks as a biological

Abstract Studies of capillary filtration (CF), which supports the isotonia of extracellular fluids in a vertebrate organism, are commonly considered within the “updated” Starling hypothesis developed on terrestrial vertebrates. This hypothesis explains the homeostasis of extracellular fluid in the body by the balance of the hydrostatic and oncotic pressures of plasma and interstitial fluid (the Starling

Abstract The features of the composition, development, and spatial distribution of the phytoplankton of highly mineralized karst Lake Klyuchik (Nizhny Novgorod oblast) are considered. The lake has a pronounced ecotone with respect to the hydrological and hydrochemical parameters. A unique algocenosis with a high quantitative development (the biomass is over 130 g/m3, which is unusual for middle-water

Abstract The composition and vertical distribution of plankton of two polyhumic bog lakes on the territory of the Volga-Kama State Natural Biosphere Reserve were studied. It was found that the anaerobic conditions were formed in the water column at a depth deeper than 2 m due to stratification and lack of light. Phyto- and zooplankton (including ciliates) prevailed in the upper aerobic layers of water

Abstract In 2008–2014, two new habitats of Cyclops bohater Kozminsky, 1933 were found in the European part of Russia, Lake Ferapontovskoe (Vologda oblast) and the Rybinsk Reservoir (Upper Volga River). The findings of this species were also confirmed for Lake Glubokoe (Moscow oblast). The morphological features and living conditions of C. bohater populations in different water bodies are described

Abstract The features of the growth and early maturation of brown trout Salmo trutta L. in the Alatsoya River (Republic of Karelia) are studied. As a rule, the age of brown trout in this river does not exceed 3 years and one of its life strategies is the formation of precocious males. Precocious males reach their puberty at age 1+; they are characterized by a larger size than parrs of the same age

Abstract The accumulation of anthropogenic radionuclides 90Sr and 134,137Cs in the marsh frog at various stages of ontogenesis is studied in the Beloyarsk Reservoir (cooling pond of the Beloyarsk nuclear plant). The Verkhnetagilsk Reservoir serves as a control (reference site). The variability of individual morphological indicators and concentrations of radionuclides in adult amphibians of the studied