Abstract The morphology of rare cryophilic species of dinoflagellates Borghiella dodgei Moestrup, Hansen & Daugbjerg from Eastern Europe (Kiev, Ukraine) has been studied. Until now, only two locations of this species—freshwater reservoirs in Italy and Portugal—were known. The original description of B. dodgei from the new locality, drawings, and photos are given in this work. The morphological variability

Abstract New data on the chlorophyll a (Chl a) content in the water of the Volga River reservoirs are presented. In years with different temperature regimes (2017 and 2018), the content of Chl a varied from minimal 2.2–13.8 to maximal 7.6–50.5 and 25.8–104 µg/L, respectively. As before, the Chl a concentration in the Volga cascade decreases from the upstream reservoirs to downstream ones; the maximum

Abstract A species of Caspian fauna, leech Archaeobdella esmonti, introduced earlier into most reservoirs of the Volga cascade, was recorded for the first time in the Uglich Reservoir in summer 2017. In 2009, A. esmonti was first detected in the Rybinsk Reservoir, where it was successfully established by 2015, and its occurrence frequency increased to 50%. The quantitative and size-weight characteristics

Abstract Information on the findings of two amphibiotic species new to Belarusian fauna, Osmylus fulvicephalus (Scopoli, 1763) and Sisyra terminalis Curtis, 1854 of the net-winged insect order Neuroptera, is reported. Data on the location, distribution, and ecological and biological characteristics of each species are provided.

Abstract The activity of glycosidases (maltase activity and amylolytic activity) in the intestinal mucosa of juvenile common carp Cyprinus carpio (L.) under a sharp increase in water temperature depends on its physiological state (satiety or starvation). The fish are acclimated to a temperature of 22°С during the summer (young-of-the-year) and winter (yearling) seasons. An increase in water temperature

Abstract The thermoadaptive characteristics of the lake minnow Rhynchocypris percnurus (Pallas, 1814) have been obtained for the first time in experimental conditions. The final preferred temperature in adult fish previously acclimated to a water temperature of 15°С is ~23°С. The sublethal temperature, as determined by a critical thermal maximum at a water heating rate of 8°C/h, in fingerlings and

Abstract In vitro studies of the effect of the herbicide Roundup (25 µg/L) on the activity of glycosidases that hydrolyze starch in the intestinal mucosa and chyme of typical (pike Esox lucius L., zander Sander lucioperca (L.), and wels catfish Silurus glanis L.) and facultative (common perch Perca fluviatilis L. and burbot Lota lota (L.)) ichthyophages have revealed the dependence of the strength

Abstract The antioxidant glutathione system (AGS) and lipid peroxidation (LP) level in tissues of the Black Sea cockle Cerastoderma glaucum (Bruguière, 1789) have been investigated and compared with those of other Black Sea bivalve mollusks with high resistance to oxidative stress (OS), namely, mussel Mytilus galloprovincialis (Lamarck, 1819) and anadara Anadara kagoshimensis (Tokunaga, 1906). The

Abstract Sixty-two species of free-living nematodes have been found in samples from four artificial reservoirs in Vietnam; one genus and eleven species are new for science. The dominant species are Dichromadorageophila (de Man, 1876); Sabatieriafoetida Gagarin, Nguyen Vu Thanh, 2008; Paradontophorafluviatilis Gagarin, Nguyen Vu Thanh, 2008; and Terschellingia longicaudata de Man, 1922. A species list

Abstract In 2013, a new species, Eurytemora caspica Sukhikh et Alekseev, 2013, was described from the northern part of the Caspian Sea. A thorough morphological analysis of Eurytemora from the Volga River basin by the original descriptors of the species has shown that E. caspica, rather than previously assumed E. affinis, actually inhabits the studied area. The species E. affinis itself was not detected

Abstract Unlike in nonregulated rivers, new ecological filters are formed in artificial reservoirs: structures (gradient zones between biotopes) which affect the behavior and distribution of juvenile fish and therefore change parameters of the downstream migration. One distinct feature of such filters is their selective effect on different species and age groups of migrants when they pass boundaries

Abstract Studies on zooplankton in the littoral zone of Bahir Dar Gulf of Lake Tana (Ethiopia) carried out in March 2018 have revealed its high qualitative characteristics and species richness (Rotifera (61 species) Copepoda (4), Cladocera (13)). High quantitative characteristics were also recorded. The maximum abundance and biomass of zooplankton were recorded in the sites with hydatophytes (the degree

The distribution of organic matter (OM), hydrocarbons, phytopigments and ecological–trophic groups of bacteriobenthos has been investigated in the bottom sediments of the internal estuaries of the small Muchke and Toki rivers. The morphological and hydrological characteristics of estuaries influence the quantitative and qualitative composition of the OM in bottom sediments. The investigation into the

Abstract A study of 2536 fish specimens of 22 species from Lake Tana in Ethiopia has revealed the presence of five species of clinostomid metacercariae represented by two genera: Clinostomum complanatum (from Enteromius humilis, E. tanapelagius, and Garra tana), Euclinostomum sp. and Clinostomum brieni (from Clarias gariepinus), and C. phalacrocoracis and Euclinostomum heterostomum (from Oreochromis

Abstract Pseudostaurosiropsisgeocollegarum (Witkowski) Morales is reported for the first time from India. This is very rare and neglected species was found from a Powai Lake in Mumbai, Maharashtra, India. This species was described from Poland. P.geocollegarum differs from other three members of the genus Pseudostaurosiropsis by the shape of the valves, size and number of striae in 10 µm. The present

Abstract Cultured hydrocarbon-oxidizing bacteria have been isolated for the first time from bacterioplankton in urban Lake Beloye (Moscow). The taxonomic positions of two bacterial strains (2012B and 2012C) isolated from this lake have been determined. Lipids of the strain 2012B comprise C14:0–C19:0 fatty acids, the most abundant of them being C15:0 (54%), C16:0 (17%), C17:0 (10%), and 10-methyl С18:0

Abstract In August 2016, the pelagic zooplankton (Cladocera, Copepoda, and Rotifera) and meroplankton (veligers of mollusks of g. Dreissena) were studied in four reservoirs of the Kama River (Kama, Votkinsk, and Nizhnekamsk reservoirs, and the Kama Reach of the Kuibyshev Reservoir). A total of 108 species were found; 14 species were new for the Kama River, including five crustaceans introduced from

Abstract The regional diversity and characteristics of rheophilic macrozoobenthos communities in the western Tien Shan are described based on 370 original quantitative samples from lotic waters in the western Tien Shan (Kyrgyzstan). We have determined altitudinal differences in the composition and structure of the communities in three zones ranging from 1000 to 3700 m above sea level. Twenty-three

Abstract The first data on testate amoeba composition from Trang An and Van Long wetlands (Ninh Binh province, Vietnam) was obtained. Sixty-three species and subspecies belonging to 9 genera and 6 families were identified from 108 samples collected from these wetlands. Arcella conica, Difflugia pulex, and D. sarissa were recorded in Vietnam for the first time. Species diversity of wetland Van Long

Abstract The effect of slow magnetic fluctuations, lighting modes, and the combination of these factors on the maturation, lifespan, brood size, and the period between hatching of juvenile specimens in Daphnia magna Straus, as well as on some morphometric parameters of the females and their offspring, have been studied. The lighting modes influence the period between the delivery of offspring and the

During a parasitological survey of nonnative fish species—rudd Scardinius erythrophthalmus—in the Rybinsk Reservoir, the metacercariae Ornithodiplostomum scardinii were found in its brain. This is the first find of this helminth in the Upper Volga basin. The rudd was infected with the prevalence 31.3%, with an intensity of 1–12 parasites per fish. Data on the current distribution of the trematode O

Abstract The level of lipid peroxidation in the hemolymph, hepatopancreas, gills, and muscles of the swan mussel Anodonta cygnea (L., 1758) of different ages has been studied. The dependence of malondialdehyde content in hemolymph and studied tissues on the age of the mollusk and structural and functional characteristics of tissues is found. The content of malondialdehyde increases in the hepatopancreas

Abstract Descriptions and illustrations are presented for a new genus and two new species of free-living nematodes found in sediments of four artificial reservoirs for shrimp aquaculture. Paradaptonema gen. n. is morphologically close to Daptonema Cobb, 1920, but it has three glands around cardia that are absent in Daptonema, as well as a peculiar structure of the reproductive apparatus in males. Paradaptonema

Abstract The species composition and abundance of zoobenthos are studied to reveal the structure of bottom invertebrate communities under the effect of biotopical, hydrological, and climatic factors. One hundred and six quantitative samples were collected from 15 pools of rapid rivers (61.6°–67.1° N) from 2003 to 2017 in eastern Fennoscandia. The basic part of the fauna is formed by 151 species, including

Abstract The results of a study of phytoplankton in Taganrog Bay in the Sea of Azov and the downstream reaches of the Don River carried out in January–November 2017 are presented. A total of 210 species of eukaryotic algae and cyanoprokaryotes are identified. An analysis of the taxonomic, ecological, and geographical composition of the plankton algal flora and seasonal dynamics of biomass of phytoplankton

Abstract The trophic structure of benthic macroinvertebrate communities in lakes varying in salinity levels (from oligohaline to hyperhaline) in the southern Ob–Irtysh interfluve has been investigated. Four trophic groups of macroinvertebrates have been identified in 48 lakes: (1) predators, (2) grinders, (3) scrapers, and (4) collectors–detritophages and facultative filter feeders. It is found that

Abstract Information on the pattern of oxygen diffusion in skeletal muscles of bony fish is discussed. This diffusion is determined by a number of variables. Endothelium of microcirculatory vessels should not be considered the main barrier for oxygen diffusion, as it has large pores and perforations. The main diffusion barrier is cytoplasmic and intracellular membranes of muscle fibers. A substantial

The article describes quantitative and structural characteristics of zooplankton of polytypic sites of a water system including a lake, canal, and a water reservoir. It is shown that in the littoral zone of lakes and water reservoirs, the number of species and communities is higher, and biomass, lower. However, in the littoral zone of shallow lake zooplankton in number, took priority due to Rotifera

Abstract Results of a study of the water temperature and phytoplankton abundance in different regions of Lake Baikal according to 15 expeditions from 1994 to 2013 during late summer are present. The spatial distribution and interannual dynamics of phytoplankton are analyzed. The total abundance of phytoplankton in late summer is shown to be high. Its average long-term value for all of the open area

Abstract On the basis of 120 original stations, macrozoobenthic communities of rivers from two adjacent areas of the Lower Amur Region (Khabarovsk krai) have been described. Rivers basins are characterized by contrasting landscape conditions: the Anyuy River basin in the piedmonts of the Sikhote-Alin mountain range and the Simmi River basin on the Amur Lowland. About 250 taxa of macroinvertebrates

Abstract Five bryozoan species of the class Gymnolaemata and a single Plumatella emarginata species of the class Phylactolaemata are found in the Caspian Sea. The class Gymnolaemata is represented by bryozoans of the orders Ctenostomatida (Amathia caspia, Paludicella articulata, and Victorella pavida) and Cheilostomatida (Conopeum grimmi and Lapidosella ostroumovi). Two species (Conopeum grimmi and

Abstract The accuracy of estimating the relative abundance of generations of fish species under conditions of incomplete initial information is analyzed. Using the example of bream from the Kuibyshev Reservoir, it is shown that, if the information on the age structure is lost for 1 to 8 years, the error in estimating the abundance of generations averages from 5 to 15%. This makes it possible to apply

Abstract Data on the dynamics of anadromous migration, age composition, body length, body weight, and morphometric characteristics of Caspian anadromous shad from the Akhtuba River are presented. Currently, Caspian anadromous shad from the Akhtuba River is monomorphic; no temporal groups have been identified. The population is represented by medium-sized young early-maturing (age of 2–3 years) fish

Abstract The influence of thyroid hormones (THs) on the organization of the exploratory behavior in fish was studied using the example of a three-spined stickleback. Strategies of fish behavior in plus maze were changed under impact of triiodothyronine. The fish treated by the hormone solution, in contrast to those of the control group, prefer shuttle movements between the corridors of the labyrinth

Abstract Chromosomal polymorphism is investigated in samples of Chironomus plumosus L., (1758) (Diptera, Chironomidae) from a pond on the Chemoshur creek in Udmurtia for the first time. The pool of polytene chromosome banding sequences of this species includes 12 banding sequences forming 17 zygotic combinations. The pluF2 sequence is found with a high frequency of 0.17. The cytogenetic distance between

Features of biomorphology of homophyllous water crowfoot Ranunculuslongirostris (Batrachium, Ranunculaceae) occurring in North America were studied. From the generally similar group of the rigid-leaved water crowfoots (the R. circinatus group), R. longirostris is distinguished by the presence of a long internode before the first flower (the ratio of leaf and internode lengths is 1 : 5), persistent

Abstract An analysis of the results of long-term observations has demonstrated changes in the species structure and a significant increase in the abundance of macrozoobenthos in the deepwater part of the Rybinsk Reservoir in extremely warm years at the beginning of 21st century. After the anomalously hot summer of 2010, the species richness and diversity decreased to their minimum values. In the following

Abstract Excavated ponds are a group of widely distributed small artificial water bodies in the territory of Central Russia. In the countryside, they play an important role as water storage for the irrigation of vegetable gardens, livestock watering, the cultivation of waterfowl, and fire water ponds. In 1998–2014, 49 village excavated ponds located in the northwestern part of Yaroslavl oblast were

Abstract Materials on the aquatic invertebrate fauna in the Maly Patok River basin (the western slopes of the Subpolar Urals) have been presented. These water bodies, which maintain the natural hydrological regime, are located on the territory of the Yugyd-Va National Park. A total of 108 taxa (except for Chironomidae) in the zoobenthos samples and the invertebrate qualitative collections taken in

Abstract In various biotopic groups of invertebrates of small rivers, the species richness and nematode abundance vary. Periphyton is poorer than meiobenthos. Along with common species, a number of worms are found only in biofouling or only in meiobenthos. A significant increase in species richness, diversity of ecological groups, and abundance of worms in meiobenthos and periphyton of small rivers