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