Vol 17, No 5 (2024)

This study presents new data on population-genetic polymorphism, phylogeny and phylogeography of two vicariant species belonging to the Daphnia longispina s.lat. complex (Crustacea: Cladocera) in northern Eurasia, D. longispina s.str. and D. dentifera. Based on the variability of the fragments of non-coding 12S rRNA and the protein coding ND2 genes of mitochondrial DNA, the demographic processes that took place in populations of this vast region have been reconstructed. The previously suggested hypothesis about the different demographic history of the “Siberian” and “European” D. longispina s.str. clades has not been confirmed, since we first revealed a deep mitochondrial divergence within the “Siberian” clade. Moreover, a new divergent lineage of D. longispina s.str. in Siberia has been identified. Nevertheless, the phylogeographic patterns of D. longispina s.str. and D. dentifera in northern Eurasia confirm the earlier conclusion that repeated, combined effects on their populations of dispersion and vicariate events occurred in different phases of the Pleistocene.

The paper presents a redescription of the parasitic nematode Philometroides strelkovi (Chromadorea: Dracunculoidea) based on the new morphometric data. New hosts from the Cyprinidae family (Rhodeus sericeus, Hemiculter leucisculus, Hemibarbus labeo) and locality – the Luchegorsk reservoir belonging to the Amur River basin (Pozharsky district of Primorsky Krai in the south of the Russian Far East) have been described. For the first time, sequences of the 18S rRNA marker gene have been obtained for P. strelkovi. On the basis of genetic data, we performed phylogenetic reconstruction and showed the clustering of P. strelkovi, separate from the sister species P. moraveci, confirmed by high statistical support at branching nodes and the size of genetic distances — 0.11–0.56% between P. strelkovi and other representatives of the genus, along with intergeneric divergence of >4%. In the light of new molecular data, the question of the artificiality of the genera Philometroides and Philometra is raised.

The manuscript presents the results of experimental studies of the adaptive potential of microorganisms that are part of the bacterioplankton of the surface and bottom water layers of the Bureiskoe Reservoir in the zone of the landslide that descended in the winter of 2018. In the summer of 2022, the structure and activity of microbial complexes from area near the landslide were studied. More than 60 strains of microorganisms of different physiological groups were isolated. On the example of 4 strains isolated from different habitats (above and below the landslide body, surface and bottom layers of water) after 30 days of freezing at a temperature of –18°C, their viability and activity in the utilization of easily available nitrogen-containing organic substances were shown. In experimental cyclic freezing-thawing, two variants of thawing were used: slow thawing in a refrigerator from –18°C to +4°C; fast defrosting over a wide temperature range from –18°C to +23°C (at room temperature). Regardless of location, all strains grew vigorously in vitro with use of a readily available peptone carbon source before and after freezing. The maximum activity on peptone was shown by strain 40 BB (below the landslide body, bottom water) in the absence of substrate change. Utilization of peptone as a source of amino acids and peptides could be accompanied by activation of the protective function against cold stress. The selected strains of microorganisms differed in their ability to transform sodium humate molecules depending on the conditions of the freeze/thaw cycles. According to the spectral characteristics, significant changes in the aliphatic and aromatic components of the humate molecule occurred with the participation of strains 45 AB and 40 BB isolated from the bottom water. These strains were more active at low thawing temperatures, which actually corresponded to the in situ temperature of the bottom water layers, which is 4–6°C. Strain 13 BS from surface water sampled below the landslide body is characterized by active transformation of the aromatic component of humic substances in a wide range of thawing temperatures (from –18 to +23°C). The results indicate that in different regions during the thawing of permafrost and the influx of specific organic substances the specific mechanisms of formation of the quality of natural waters may manifest.

New associated data on the content of chlorophyll a and its derivatives in the water and bottom sediments of Busse Lagoon (Sakhalin Island) have been obtained. Chlorophyll a and chlorophyll degradation products (Chl a + Ph) in the water column is represented predominantly by the active form (61.4 ± 1.1%), in bottom sediments – by a product of its degradation (84.7 ± 2.5%). The connection between pigments in water and bottom sediments, as well as the abiotic conditions of primary production, has been revealed. For the first time, for a unique reservoir characterized by overgrowth of aquatic vegetation, silt accumulation and regular death of aquatic organisms, the similarity of the average annual sedimentation rate in the lagoon with the ratio of pelagic and benthic pigments was shown. The prevailing importance of the biotic factor in the formation of trophic conditions has been established. Based on the average content of Chl a + Ph in water (4.1 ± 0.8 mg/dm³) and in bottom sediments (13.5 ± 4.0 μg/g d.s.), Busse Lagoon is a mesotrophic reservoir. Trophic state of benthic in the period 2013–2021 is preserved, remaining oligotrophic in the shallow coastal zone and mesotrophic in the central part of the lagoon.

The main structural characteristics of the summer macrozoobenthos of the Rybinsk Reservoir have been studied according to the data of the expanded grid of stations in 2019 and 2021. 80 species and forms of benthic invertebrates were identified, most of which were chironomids, oligochaetes and mollusks. In all zones and parts of the reservoir, the basis of benthos species richness is represented by chironomids. The dominant complex on all soils included Limnodrilus hoffmeisteri Claparede, 1862, in most cases – Chironomus f. l. plumosus, with the exception of silted sand, where Cladotanytarsus gr. mancus and Tubifex newaensis (Michaelsen, 1902) were added to them. On the silted-up shell, the dominants included Potamothrix moldaviensis Vejdovsky et Mrazek, 1902. The basis of the quantity (93%) and biomass (86%) of animals were chironomids and oligochaetes. The greatest abundance of benthic invertebrates was recorded on gray silts and in the deep-water zone of the reservoir. The Sheksninsky part was characterized by the largest benthic biomass, and the Volzhsky part was characterized by the largest quantity. Among the trophic groups in the quantity of macrozoobenthos on all main soils, in all parts, in the deep-water zone and estuarine areas of the tributaries of the reservoir, the basis was formed by detritophages–swallowers. In the zone of open shallow water, phytodetritophages–filtrators + collectors dominated in quantity. This trophic group made the greatest contribution to the benthic biomass of gray and peaty silts, in all zones and parts, except the Volzhsky part. On silted-up shell, the largest share in the total biomass was made up of phyto-detritophages–filtrators + collectors and detritophages–swallowers. Detritophages–swallowers formed the main part of benthic biomass on silted sand and in the Volzhsky part. When conducting a comparative analysis with the results obtained in 1978, a decrease in the biomass of oligochaetes on gray silts was recorded by ~3 times. Likely, this is due to a decrease in the occurrence and abundance of a large oligochaete that previously dominated on gray silts, an indicator of β-mesosaprobic conditions, Tubifex newaensis. In 2019 and 2021, this oligochaete was not included in the dominant complex of gray silts. It began to be represented by polysaprobes Limnodrilus hoffmeisteri. This can serve as an indirect sign of an increase in the trophic status of a reservoir to a typically eutrophic one and an increase in the accumulation of organic matter in soils.

The paper describes typical habitats of the European river lamprey (Lampetra fluviatilis (L., 1758)) larvae in the rivers of the Leningrad Region. The density of ammocoetes, abiotic components of biotopes, as well as the structure of benthic and planktonic algae communities, zooplankton, and macrozoobenthos were estimated. It has been shown that the preferred soils for larvae are sands <0.25 mm. Oligochaeta and Chironomidae larvae reached high levels of quantitative development together with ammocoetes. Algae and zooplankton communities were not decisive for lamprey larvae and have expressed seasonal patterns with peaks of abundance in the spring. The part of lamprey larvae in the abundance of benthic coenoses can reach significant values – the part in the total biomass of macrozoobenthos was 30–80%.

The biological characteristics of warm-water fish species living in water bodies of the Arkhangelsk region are presented. Changes in size and mass parameters, age and sex structures and reproductive ability of the Severodvinsk sterlet in the temporal aspect were revealed. It has been established that it has good growth rates, a reserve in replenishing the spawning stock and a stable state of the natural reproduction system. The biological parameters of blue bream and rudd, rare species of fish that live in the lakes of the Kenozersky National Park, as well as a number of reservoirs in the Arkhangelsk region, were obtained. The biological characteristics of species that appeared in the river basin are considered. Northern Dvina as a result of self-dispersal - white-eye and asp, as well as the nutrition and feeding relationships of white-eye with native fish species. The attention of specialists to these alien fish species is due to the need to develop an environmental forecast for the development of the situation with their numbers in the context of ongoing global warming.

The diatom alga Nitzschia cf. thermaloides can be found in large numbers in puddles and lakes in the places where mud volcanoes function in the area of the Bulganak mud volcano field (eastern Crimea). Environmental conditions in such reservoirs are extreme: salinity is from 18 to ≥70‰, insolation is extremely high, and ultraviolet radiation is very strong. The growth rate and the intensity of sexual reproduction of N. cf. thermaloides at different salinity and illumination levels have been studied in laboratory conditions. We have determined the limits of halotolerance and the optima of salinity and illumination for growth and sexual reproduction of the alga, capable of vegetative reproduction in an environment with salinity from 0 to 220‰. The range for sexual reproduction is narrower, from 6 to 54‰. The salinity of 22–25‰ and illumination of about 1.5 klx are optimal for both vegetative and sexual reproduction of N. cf. thermaloides.

Data from coagulograms of rainbow trout Oncorhynchus mykiss (Walbaum, 1792), african sharptooth catfish Clarias gariepinus (Burchell, 1822) and common scaly carp Cyprinus carpio (L., 1758) obtained by clotting methods at plasma incubation temperatures of 43°C, 40°C, 37°C, 24°C, 28°C and 18°C were analyzed. It was revealed that in catfish and carp the internal pathway predominates in the activation of blood coagulation, and in trout the main ones are the formation of a clot along the internal and general pathways. The amount of soluble fibrin-monomer complexes in trout is the highest of all fish studied. Hypo- and hypercoagulable states in the plasma hemostasis of the studied fish species in vitro were established at both low and high temperatures of the reaction medium. Fibrinogen and antithrombin III exhibit thermolabile at temperatures other than 37°C. Correlation and regression analysis showed that the most closely related to changes in temperature in carp are prothrombin time (PT), and the activity of fibrinogen and antithrombin III in catfish. A change in PT of 50% can be explained by the influence of the temperature factor, and the fibrinogen and antithrombin III activity by 77% and 52%, respectively. The identified patterns can become the basis for determining the boundaries of thermal adaptation of fish and developing biomarkers of heat stress.

The importance of fish as a component of healthy nutrition and as a high-quality source of nutrients in the human diet has increased in recent years. To assess the nutritional value of the six main commercial fish species (common roach Rutilus rutilus, common bream Abramis brama, crucian carp Carassius carassius, crucian carp Carassius carassius, common carp Cyprinus carpio, European perch Perca fluviatilis, and northern pike Esox lucius) from the Barguzin River (Eastern Cisbaikalia), the FA composition and lipid quality indices of the muscle tissues have been determined. The FA composition of the dorsal muscle tissue of fish has been analyzed by direct methanolysis. The total content of SFAs ranges from 26 rel. % in carp to 37 rel. % in bream, MUFAs from 17 rel. % in perch to 32 rel. % in carp, and PUFAs from 42 rel. % in bream and carp to 54 rel. % in pike. The dominant FAs are palmitic 16:0 (17.5–29.2 rel. %), oleic 18:1(n-9) (17.5–29.2 rel. %), and stearic 18:0 (5.0–8.0 rel. %) acids, as well as PUFAs, including essential docosahexaenoic 22:6(n-3) (9.7–24.9 rel. %), eicosapentaenoic 20:5(n-3) (9.2–19.1 rel. %), and arachidonic 20:4(n-6) (6.9–10.1 rel. %) acids. The Σ(n-3)/Σ(n-6) ratio of PUFAs is 2.8–4.6, which is typical for freshwater fish. Relatively high nutritive value index (NVI), values of the health-promoting index (HPI), and ratio of hypercholesterolemic to hypocholesterolemic FAs (HH), the as well as the atherogenicity and thrombogenicity indices (<1), indicate the high nutritional value of the muscle tissue of the studied fish species. According to the content of (n-3) PUFAs and high total ratio of eicosapentaenoic and docosahexaenoic acids, the most valuable species are European perch and northern pike.

Anthropogenic pollution of the aquatic environment with microplastics is one of the most urgent but least studied problems of modern ecotoxicology. The review, based on recent literature data, provides an analysis of studies in the field of absorption, bioaccumulation, and biological effects of microplastic exposure in freshwater bivalve molluscs (Bivalvia). A total of 22 studies have been conducted so far, which were performed on representatives of three families: Cyrenidae (45), Unionidae (25) and Dreissenidae (30%). The conducted studies are represented by field observations (43.5), field (8.7) and laboratory (47.8%) experiments. It has been shown that freshwater bivalves, as active filters, are able to absorb and accumulate in soft tissues (gills, hepatopancreas) microplastic particles from both water and bottom sediments, perceiving them as food objects. Bioaccumulation of microplastics in molluscs leads to functional and structural disorders in the body. The joint action of microplastics and other pollutants (cadmium, polychlorinated biphenyls, pharmacological drugs) can cause both synergistic and antagonistic effects in the biological responses of molluscs. Based on the conducted studies, it is suggested to use bivalve molluscs as organisms-bioindicators of freshwater pollution with microplastics.

The hypothesis that aquatic macrophytes produce and include in their low molecular weight metabolome fewer fatty acids (in composition and content) under anthropogenic impact (eutrophication and pollution) than in clean, undisturbed, or slightly disturbed aquatic habitats (oligotrophic and mesotrophic conditions) was tested for the first time. The available data really give grounds to definitely speak about a decrease in the specific production of saturated and unsaturated fatty acids by macrophytes per unit of their biomass with an increase in the processes of eutrophication and pollution in aquatic ecosystems. The use of this pattern for the indicator assessment of anthropogenic influence on aquatic ecosystems is a significant practical application of this regularity.