No 3 (2023)

For the first time, diatoms from the Beloyarskoe, Chernoistochinskoe and Nizhnetagilskoe reservoirs of the Sverdlovsk region are studies using electron microscopy. The data on the species composition of Bacillariophyta of the Chernoistochinskoe Reservoir are significantly supplemented. A total of 216 taxa of species and intraspecific rank from 63 genera are identified in these three reservoirs. Among them 17 taxa are new to the flora of Russia, 14 forms from 11 genera are identified only to the genus. The maximum taxonomic diversity is recorded in the Nizhnetagilskoe reservoir (179).

Two new nematode species of the genus Daptonema, D. brzeskii sp. n. and D. rivale sp. n., are described and illustrated based on the material collected from Mekong River Delta, Vietnam. Daptonema brzeskii sp. n. is close to D. lutosum Gagarin, 2021, D. dihystera Gagarin, Nguyen Vu Thanh, 2005 and D. hyalocella Aryuthaka, Kito, 2012 in the presence of postvulval uterus sac, and it is close to D. paraoxyuroides Nguyen Dinh Tu, Gagarin, Nguyen Vu Thanh, Nguyen Thi Xuan Phuong, Nguyen Thanh Hien, 2014 in the shape of spicular apparatus. From the former species it differs in the thinner body, slenderer tail, narrower labial region, shorter outer labial setae and spicules, larger pharyngostoma, and vulva located farther from the anterior body end. It differs from D. dihystera in the shorter body, narrowed labial region, shorter outer labial setae and spicules, and larger pharyngostoma. Daptonema brzeskii sp. n. differs from D. hyalocella in the thinner body, amphidial fovea located closer to the anterior body end, shorter outer labial setae, longer spicules, presence of gubernaculum, larger pharyngostoma, and vulva located farther from the anterior body end. From D. paraoxyuroides, D. brzeskii sp. n. differs in the presence of postvulval sac, longer body, slenderer tail, shorter outer labial setae and gubernaculum. Daptonema rivale sp. n. is similar to D. setihyalocella Aryuthaka, Kito, 2012 in shape of spicular apparatus and to D. brzeskii sp. n. in the shape of pharyngostoma. Daptonema rivale sp. n. differs from D. setihyalocella in the shorter and comparatively thinner body, shorter outer labial setae, spicules, and gubernaculum, bigger pharyngostoma, and vulva located farther from the anterior body end. Daptonema rivale sp. n. differs from D. brzeskii sp. n. in the longer body and outer labial setae, less slender tail, and vulva located farther from anterior body end.

For the first time general quantitative (number, biomass) and structural (morphological, dimensional) indicators of bacteriobenthos in different morphotypes of bottom sediments of the lake Kandry-Kul (Republic of Bashkortostan) were determined. The total number of bacteria was 1.8–11.8 × 10⁹ cl./ml, and the biomass was 106–1344 mcg/mL. Two types of seasonal dynamics of abundance and biomass of deep-wate and coastal bacteriobenthic communities were identified. The influence of heterogeneity of bottom sediments on quantitative indicators and morphological structure of lake bacteriobenthos is considered. The increase in pelitic and aleritic fractions in the mechanical composition of silts contributes to an increase in the total number of bacteria and the restructuring of the morphological structure of bacteriobenthos towards an increase in the number of coccous forms. The proportion of cocci increases with an increase in the percentage of saprophytes in the total number of bacteria.

The genus Hydrocharis L. combines free-floating, occasionally rooting obligate pleistophytes and rooting hydrohelophyte, which are edificators and subedificators in freshwater vegetation communities. How ecologically similar are these closely related species? It has been found that Hydrocharis dubia (Blume) Backer. and H. morsus-ranae L. are conditionally freshwater alkaliphilic mesoeutrophic, ortho-, mesoalluviophilic detrito-, psammopelophiles. Ecologically H. chevalieri (De Wild.) is isolated, it is a freshwater acidoneutrophilic meso-, mesoeutrophic, ortho-mesoalluvialophilic species indifferent to the mechanical composition of bottom sediments. The coenocomplex of H. chevalieri is characterized by abundance of helophyte communities; in the composition of the coenocomplex of two other species hydatophyte and pleistophyte communities play a key role. Communities with species of the genus Hydrocharis are characterized by simple synmorphology, relatively high species richness, and a high proportion of low-abundance species.

In the Sevastopol Bay, degradation of species composition and communities of the zoobenthos began to be shown in the 20's–30's years and has reached maximum demonstration in the 60s–90s years of the last century. Only five species of macrozoobenthos were the most resistant at high anthropogenous loadings and eutrophication in those years. The relative recovery of the species composition and the improvement of benthic biological parameters are observed in the bay since the beginning of the 21st century. The zoobenthos was replenished by 39 new species which here were not marked earlier. Mollusca, Crustacea and Polychaete, among taxonomic groups of zoobenthos, had the greatest quantity of new species. Registration of the zoobenthic animals even in areas, which were earlier as “dead zone”, indicates an improvement of habitat in the Bay. The reduction of the eutrophic level, the oxygen regime improvement and the area expansion with oxidizing conditions in bottom sediment were the major factors in improving benthic habitats in the Sevastopol Bay. These ecological changes coincided with increase of water temperature in the summer period. The positive tendencies for a zoobenthos are typical for the Romania, Bulgarian coasts in the last decade.

Age composition and fecundity of taimen Hucho taimen (Pallas, 1773) spawners at spawning grounds located in left tributaries of the Lena River (Muna and Motorchuna rivers) analyzed. Spawning season take place during May–June. Spawners age varies from 8 to 17 years. Absolute fecundity of taimen from Muna and Motorchuna rivers is more than in taimen from western part of species range, and smaller than in populations from eastern part of range. Taimen individuals from river under study are part of large population of the species in the Lena River. They forage and overwinter in the Lena River and enter its tributaries including Muna and Motorchuna rivers only for reproduction. It is typical for taimen from basins of other large rivers (Kama, Yenisei, Amur). Stock abundance of taimen is not large. Spawners at spawning sets needs special protection measures.

This study reports the presence of Cobitis strumicae Karaman, 1955 in Terme Stream (Samsun-Black Sea-Turkey). Molecular and morphometric approaches were used together to prove the existence of the species in Terme Stream. The family Cobitidae represents a unique element of ichthyofauna. Even while sexual dimorphism can take many different forms, taxonomy studies have only used a small number of morphological features, leaving many concerns unanswered. In addition to the assessments of phenotypic traits (Gambetta’s longitudinal zones, Canestrini’s scales, suborbital spine morphology, barbel and mental lobe morphology), mitochondrial cytochrome b gene (cyt b) (1140 bp) sequence variation was studied in molecular analysis. We present the phylogenetic relationships of morphologically diagnosable subgenus Bicanestrinia from Asia Minor and Balkans in here. Samples from Terme (Accession Numbers: ON116344 and ON116345) and GENBANK were combined in the phylogenetic analysis. Our findings offered a significant distribution update of C. strumicae from Terme Stream, a southern coastal Black Sea drainage, and support the vicariance theory, according to the results of this study.

The protein composition of the incubation medium and extracts of various types of cestodes inhabiting the intestines of freshwater fish was investigated. Proteins with apparent molecular weights from 10 to 312.5 kDa were found in both biological media of worms. In most of the investigated worms, 64 to 82% of the protein bands in the incubation medium and the extract have an apparent molecular weight below 50 kDa. An assumption was made about the importance of these proteins in the vital activity of helminths and the need to concentrate further efforts on the study of this particular component of the proteome.

Bream, Abramis brama (L.), is an important commercial species and the object of monitoring pollution of freshwater bodies with polychlorinated biphenyls (PCBs). However, the dependence of the PCB content on the age of the bream has been studied very poorly. In this regard, the concentrations of 32 PCB congeners were measured in the carcasses of female bream of different ages in the pre-spawning period. It is shown that the concentration of PCBs in the body lipids increases from 257 to 449 ng/g over a period of 8 to 19 years. In terms of wet weight, the concentration of PCBs increases from 19.8 to 57.9 ng/g over a period of 8 to 13 years and then decreases to 21 ng/g at the age of 19 years. The largest share was 5-XB – from 46 to 58%, then 6-XB – from 17 to 29%, 4-XB – from 12 to 18%, 3-XB – from 4 to 8%, 7-XB – from 4 to 6% and 2-XB – from 0.1 up to 0.5%. PCB concentrations 5/8, 28, 31, 44, 49, 52, 74, 70/76, 87/115, 95/66 do not depend on age (R² < 0.5); PCBs 97, 99, 105, 90/101, 110, 118. They have an average dependence (0.5 < R² < 0.6); PCBs 138, 153, 180, 183, 128/167 and 170/190 strongly depend (R² ≥ 0.7). With age, the congener composition changes towards an increase in highly chlorinated PCBs. The content of PCBs in the carcass of bream of the Volga Ples of the Rybinsk reservoir does not exceed the existing in Russia MPC in fish, amounting to 2 mg/kg of raw weight. The average indicator of non–carcinogenic risk exceeds 1 (0.82–2.39), which indicates the possible development of non-carcinogenic diseases in target organs and systems. The indicator of carcinogenic risk exceeds the level of negligible risk (1 × 10^–6) and corresponds to the range 2 – the maximum permissible risk or the upper limit of acceptable risk (1 × 10^–6–1 × 10^–4). These risks are subject to constant monitoring, the population is recommended to limit the consumption of large fish with a high fat content.

It is shown that it is possible to determine the natural mortality of fish, using the example of muksun (Coregonus muksun) and peled (Coregonus peled) of the Ob River, by constructing dependences of the decrease in the number of generations. It is established that the dynamics of mortality has a U-shaped form. The minimum mortality rates are at the age when sexual maturity reaches more than 70% of individuals. The influence of various natural and anthropogenic factors on natural mortality is shown. It is noted that periodically occurring deficiency of dissolved oxygen has a significant impact on the wintering fish in the southern part of the Gulf of Ob. There was an increase in mortality during fish migrations and this fact can serve as one of the criteria for the periodicity of whitefish spawning. It is established that numerous generations of favorable years of feeding and reproduction are characterized by a higher survival rate of individuals. The presence of genera-tions with different degrees of survival is an important adaptive property of populations.

The first data on the pigment characteristics of higher aquatic plants in the Rybinsk Reservoir (Upper Volga, Russia) are presented. The average content of chlorophyll a is 7.5 ± 0.6 mg/g organic matter in leaves, and 4.0 ± 1.4 mg/g organic matter in stems, or 6.1 ± 0.5 and 3.3 ± 1.2 mg/g dry plant material, respectively. The average carbon/chlorophyll a ratio is 76 ± 6.2 in leaves and 408 ± 150 in stems. Helophytes, which dominate in the reservoir in terms of biomass and overgrowth area, are distinguished by a record concentration of organic matter (90.2 ± 0.8%). The concentration of chlorophyll a and the relative content of carotenoids depend on environmental conditions and plant species.