Vol 12, No 2 (2019)

Data on the first recorded marine alga Prorocentrum leve Faust, Vandersea, Kibler, Tester & Litaker (Dinophyceae) in a Russian inland waterbody, the hypersaline Lake Manych-Gudilo, are given. As a result, in May, July, and October 2016 and February 2017 it was revealed that the species was found in small quantities, mainly in the northwestern part of the lake. Its morphology, studied with an electron scanning microscope, is largely consistent with that described in the literature. The presence of marine species P. leve can serve as indirect evidence of the fragmentation of marine algal areas as a result of paleobasin regression. The results expand information on the composition of the algal flora of inland water bodies in Russia, as well as on the environmental opportunities and general distribution of P. leve.

A morphological analysis of the populations of rotifer Kellicottia bostoniensis (Rousselet, 1908) from 23 waterbodies in European Russia has been made. It is shown that the length of the posterior spine is the most variable character; the length of the lorica is the least variable one. There is a positive correlation between the length of anterior and posterior spines. The length of spines increases with an increase in lorica length. The sizes of rotifers differ in waterbodies with different trophic statuses, depths, and pH values. The body size of K. bostoniensis is larger in mesotrophic, acid, and deep waterbodies.

Data on the composition, content, and interannual dynamics of photosynthetic pigments in water of the Upper Volga reservoirs in the summers of 2005 and 2012–2016, continuing the series of long-term observations, are given. With an average content of chlorophyll (Chl a) from 13.1 ± 1.4 to 52.5 ± 2.7 μg/L in the Ivankovo Reservoir and from 7.6 ± 1.6 to 27.5 ± 2.5 μg/L in the Uglich Reservoir, an increase in Chl a is observed after the anomalously hot 2010. Interannual changes in Chl a in dependence on the water temperature, as well as the Wolf numbers and North Atlantic Oscillation index (NAO) that indirectly affect phytoplankton productivity, are analyzed. Chl a content in the Ivankovo Reservoir, which retains the eutrophic status, does not go beyond the long-term fluctuations, while an increase in the absolute and relative amounts of Chl a in the Uglich Reservoir indicate an increased role of blue-green algae and transition of the reservoir to the eutrophic category.

The distribution and population dynamics of Ostracoda and their response to environmental factors have been analyzed in Crimean hypersaline lakes based on data from a long-term monitoring study (2005–2016). Only one representative of this class, Eucypris mareotica (Fischer, 1855), occurs in these lakes. The species was recorded in the Crimean lakes at a maximum salinity of 300 g/L. The frequency of occurrence of this species correlated negatively with salinity. This species reached high abundances in plankton (650 000 ind./m³), benthos (565 000 ind./m²), and floating mats of filamentous green algae Cladophora spp. (9 900 000 ind./kg of wet weight of the mat). Ostracods were shown to reduce the concentration of calcium and magnesium in the water as a result of using these elements for the construction of their shells. The possibility of using the shells of ostracods for paleoclimatic and palaeolimnological reconstructions was discussed.

The composition of macrozoobenthos in experimental mesocosms has been studied. A total of 116 invertebrate taxa are found, with chironomids (50 species), mollusks (25), and oligochaetes (21) the most widely represented. Most of the revealed taxa (61%) are common for Dreissena polymorpha (Pallas, 1771) biocenoses in the Rybinsk Reservoir; other species have invaded mesocosms during the experiment. The minimal number of invaders is found in mesocosms with perch larvae; the maximal is in both variants with the zebra mussel. It is shown that in the absence of zebra mussels those age groups of perch consuming macrozoobenthos reduce its main structural characteristics. The maximum sum of the main structural characteristics is recorded in mesocosms with yearlings of perch and zebra mussels. This indicates a positive environment-forming role of Dreissena polymorpha in benthic communities and the possibility that other invertebrates can use its druses as refuge.

The adaptive features of the Siberian sturgeon (ecology, species structure, nutrition, age structure, and reproduction) have been found both at species and population levels, as well as an extremely large norm of reaction underlying its plasticity, on the basis of a comparative analysis of ecological and morphological features of the closely related Russian and Siberian species of sturgeons. The extremely wide range of the norm of reaction makes it possible for relatively young species of the Siberian sturgeon to occupy vast areas and form life strategies inherent for the populations inhabiting the environment characterized by different thermal and trophic conditions.

The specific features of accumulation of fat, protein, mineral, and nitrogen-free extractive substances in the skeletal muscles of bream (Abramis brama L.) from areas of the Rybinsk reservoir subjected to different degrees of anthropogenic load have been studied. Data on the bream forage base and feeding in the reservoir are presented. It is shown that, in the areas of the Sheksninskii Reach with high food capacity located in the zone of long-term local anthropogenic pollution, the feeding intensity of bream decreases. This leads to a decrease in fish conditions and amount of fat and mineral substances in their muscle tissues when compared with specimens from conditionally clean stations in the Mologa and Volga reaches with high food capacity.

For the first time the activity of casein-lytic and hemoglobin-lytic peptidases of intestinal mucosa, chyme and enteric microflora of carnivorous boreal fish (pike, zander, burbot, perch) was investigated across a wide temperature range (0–70°С) to reveal the role of the enzymes of the enteric microbiota and the prey in the temperature adaptations of the digestive system of these fish. It was shown that in summer at 0°С, the relative activity of peptidases of intestinal mucosa (less than 20%) is usually considerably less than that of chyme and enteric microflora peptidases (up to 40% of maximal activity). In winter, on the background of low relative activity of mucosa and enteric microbiota peptidases at 0°C revealed a high level of the relative activity of burbot and pike chyme peptidases (45 and 80% of maximal activity). The role of enteric microbiota and prey peptidases in digestive system adaptations of piscivorous fish to low temperatures is discussed.

The in vitro effect of Roundup herbicide at a concentration of 25 μg/L on the activity and temperature characteristics (temperature dependence, activation energy E_act, and Q₁₀ temperature coefficient) of maltase in the intestinal mucosa of the juvenile sander, perch, roach, and common carp has been studied. The magnitude and direction of the effect depends on the fish species and the incubation temperature. Roundup does not affect the temperature optimum for maltase (60°C for perch and sander; 50°C for roach and carp). The lower relative activity of the enzyme in the temperature range of 0–30°C indicates a decrease in the efficiency of maltose hydrolysis, while lower E_act values indicate adaptive changes in this parameter in the presence of Roundup.

Two Cymatopleura species are found in aquatic ecosystems of North Vietnam: C. aquastudia Kociolek & You 2017 and C. xinjiangiana You & Kociolek 2017. The main qualitative (valve shape) and quantitative (morphometric characteristics) taxonomic data are given. The species are illustrated by original LM microphotographs.