Gene expression levels of myogenic regulatory factors (MRF, myf5, myog, myod1, myod2), myosin heavy and light chains (myhc, mlc-2), myostatin, and GH/IGF axis components (ghr1, ghr2, igf1, igf2, igfr1a, igfbp2a) were studied in the muscles and liver of a rainbow trout (Oncorhynchus mykiss Walb) farmed under conditions of continuous (24-h) lighting with night feeding to assess the impact of such a rearing regimen on growth regulation in this valuable commercial species. The introduction of a new rearing protocol into rainbow trout aquaculture (implemented in the Republic of North Ossetia-Alania) affected the gene expression of MRFs (myf5, myog, myod2) and muscle proteins (myhc, mlc2), as well as GH/IGF axis components in muscles (igf2, ghr2) and the liver (ghr1). Fish reared under continuous light demonstrated higher expression levels of myf5, myhc and mlc-2 genes compared to those raised under natural lighting, which also corresponded to their growth rates. The different patterns of changes in the expression of igf2, ghr1 and ghr2 genes in the muscles and liver in response to the introduction of continuous lighting were found. By November, individuals from both control and experimental groups showed an increase in the expression of igf1, igf2, igfr1a, ghr2, igfbp2a genes in the liver, as well as igfr1a and mstn1a genes in muscles, which was consistent with an increase in their relative growth rates. The results indicate differences in myogenesis regulation depending on lighting conditions.

Представлены данные об изменении активности мембраносвязанного фермента осморегуляции Na+/K+-АТФазы и липидного состава в жабрах горбуши Oncorhynchus gorbuscha при нерестовой миграции из Белого моря в речную среду через эстуарий. Компенсаторная реакция горбуши в гипоосмотической среде сопровождается снижением активности Na+/K+-АТФазы и изменением содержания фосфатидилсерина и полиненасыщенных жирных кислот (линолевой, эйкозапентаеновой и докозагексаеновой). Полученные результаты свидетельствуют о позволяющей реализовать репродуктивную стратегию эффективной осморегуляции у горбуши при нерестовой миграции из моря в реку.

Purpose of the review: analysis of the effect of the photoperiodic factor based on indicators of lipid metabolism in Salmonid and Cyprinid fish species.Methods used: comparative analysis of literature and own experimental data.Results: The length of daylight (photoperiod) is one of the most important abiotic factors affecting the behavior, reproduction, metabolism, growth and development of fish. The changes in the lipids and fatty acid constituents execute a significant role in the adaptation of aquatic organisms to new light conditions. Certain parameters of lipidogenesis can serve as a reliable indicator of the normal route of metabolic processes in the organism. It is widely known that photoperiod regimes are used in aquaculture to optimize the cultivation of various species of aquatic organisms, including the most common Cyprinids and Salmonids. The specificity of the reaction of lipid metabolism to the effects of various lighting modes is shown: in cyprinids, the reaction can be multidirectional depending on the species (including its absence), while in Salmonids on example of Atlantic salmon, a change in the lipid profile in the direction of smoltification is observed. The role of combining the photoperiod with other factors, such as feeding and climatic features of the region, are discussed.Significance: The results can contribute to a better understanding of the adaptive processes in fish and optimize the conditions for their artificial rearing.

Gene expression levels of the myosin heavy chain (myhc) and myosin light chain 2 (mlc2), myogenic regulatory transcription factors (myf5, myog, and myod1 paralogs), myostatin paralogs, and insulin-like growth factors 1 and 2 (igf1 and igf2) were studied in the muscles of salmon fingerlings farmed under different lighting and feeding conditions at a constant water temperature in the Republic of North Ossetia-Alania (Russian Federation). The combined effect of different lighting and feeding regimes affected myhc, mlc2, myod1a, myf5, myod1b, and myod1c gene expression. The individuals reared under constant lighting conditions were distinguished by higher expression levels of myf5, myhc and mlc2 genes compared to fish reared under natural light, which also corresponded to their higher growth rates. The expression levels of IGF genes varied in different ways throughout the experiment: igf1 gene expression constantly increased, while igf2 gene expression increased during the first month of a study and decreased thereafter. The results indicate differences in the processes of myogenesis regulation depending on lighting and feeding conditions.

The photoperiod is an important ecological factor synchronizing the endogenous rhythms of growth and development of the Atlantic salmon Salmo salar L. The changes in the FA content of phospholipids (PL) and triacylglycerols (TAG) during the growth and development of Atlantic salmon juveniles (fingerlings, parrs, and smolts) at different lighting and feeding regimes in aquaculture of the southern region (North Ossetia, Alania) were studied. A high content of saturated fatty acids (SFA) and a consistently high content of polyunsaturated fatty acids (PUFA) in PL (more than 40

We studied the activity of energy and carbohydrate metabolism enzymes (cytochrome c oxidase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, 1-glycerophosphate dehydrogenase, pyruvate kinase, and aldolase) in the muscles and liver of rainbow trout of three size groups with ages of five, ten, and 12 months under the influence of two types of commercial feeds with different composition. The levels of activity of the enzymes G6PDH, 1-GPDH, and aldolase in the liver were significantly higher in fish from the “feed no. 2” group. The identified differences in the activity of enzymes in the liver of fish suggest that feed no. 2 to a greater extent (compared to feed no. 1) promotes the use of carbohydrates in lipid biosynthesis. Differences in the activity of the enzymes COX, LDH, aldolase, G6PDH, and 1-GPDH in the liver and muscles of fish depending on the month of sampling and size group are most likely associated with changes in the metabolism of fish as their weight increases towards generative metabolism.

Activities of key enzymes of energy and carbohydrate metabolism (cytochrome c oxidase (COX), lactate dehydrogenase (LDH), aldolase, glucose 6-phosphate dehydrogenase (G6PDH), and 1-glycerophosphate dehydrogenase (1-GPDH)) were studied in pink salmon Oncorhynchus gorbuscha (Walb.) smolts from the White Sea in a cage experiment simulating the transition from a freshwater to a marine environment. A decrease in COX, G6PDH, and 1-GPDH activities and an increase in LDH and aldolase activities were observed in juveniles with an increase in water salinity. Based on the findings, a redistribution of energy substrates between the reactions of aerobic and anaerobic metabolism towards higher anaerobic ATP synthesis was assumed for pink salmon. This may indicate that adaptive mechanisms rearrange metabolism to provide energy for osmoregulation in pink salmon juveniles when the salinity changes in their habitat.

The relative level of gene expression of enzymes, like desaturases and elongases (fadsd5, fadsd6, elovl2, elovl5a, and elovl4), which play a key role in the biosynthesis of long-chain polyunsaturated fatty acids, was studied in the liver of juvenile Atlantic salmon Salmo salar Linnaeus, 1758, reared under different lighting and feeding regimes in aquaculture conditions. The level of the fadsd5 desaturase gene expression was higher in Atlantic salmon smolts (0+) reared under regime of round-the-clock lighting and feeding compared to smolts from the experimental group with a natural photoperiod and daylight feeding. Changes in the level of gene expression (elovl2, elovl5a, and fadsd5) in juvenile Salmo salar reflect adaptive processes at the molecular genetic level during the growth and development of fish and in response to changes in environmental conditions. The obtained results make it possible to assess the capability/requirements for the biosynthesis of PUFAs in juvenile salmon during its growth and development.

The activity of energy and carbohydrate metabolism enzymes (cytochrome c oxidase, pyruvate kinase, glucose-6-phosphate dehydrogenase, glycerophosphate dehydrogenase, lactate dehydrogenase, aldolase) was studied in rainbow trout Oncorhynchus mykiss Walb. grown in aquaculture conditions at an enterprise in North Ossetia-Alania under a regime including 24-hour lighting and night feeding. According to the results of the study, the activity of cytochrome c oxidase and pyruvate kinase in the liver of fish from the experimental group was significantly higher than in the control individuals, indicating an increase in the aerobic metabolism level of ATP synthesis. The activity of aldolase in the organs of fish grown under 24-hour lighting was lower compared to fish from the control group, indicating a decrease in the level of carbohydrate utilization in glycolysis in muscles and the intensity of gluconeogenesis in the liver. The differences revealed suggest that with the introduction of 24-hour lighting and night feeding, metabolic changes are observed in energy and carbohydrate metabolism, facilitating biosynthesis processes and, accordingly, an increase in fish weight.

The biochemical mechanisms of the effect of additional lighting on the growth and early development of salmonids in aquaculture allowing identification of patterns of slow or accelerated growth, as well as the onset of the smoltification, are studied. The results of changes in lipid status in parr and smolts of Atlantic salmon after the “winter window” (December–January) are presented. These results were obtained from three experimental groups exposed to different lighting and feeding regimes at the fingerling stage. The changes in lipid composition of the studied young salmon indicate the onset of smoltification in all experimental groups. However, this effect is the most pronounced in the fish previously reared under 24-hour lighting during the summer–autumn season.

This review presents the main modern ideas about the biosynthesis of long-chain polyunsaturated fatty acids in teleost fishes and about the genes encoding key enzymes, desaturases and elongases, involved in this process. The authors summarized basic information about the set of elongases and desaturases genes and the features of their functioning in the Atlantic salmon Salmo salar and the rainbow trout Oncorhynchus mykiss, as the most studied and valuable commercial salmon species. The data can be used when conducting research to improve and modify the biotechnology of fish farming with the possibility of targeted regulation of lipogenesis (primarily to control the content of essential FAs) in their body.

Data are presented on changes in the activity of the membrane-bound osmoregulatory enzyme Na+/K+-ATPase and lipid composition in the gills of pink salmon Oncorhynchus gorbuscha during spawning migration from the White Sea to the river environment through the estuary. The compensatory reaction of pink salmon in a hypoosmotic environment is accompanied by a decrease in Na+/K+-ATPase activity and a change in the content of phosphatidylserine and polyunsaturated fatty acids (linoleic, eicosapentaenoic and docosahexaenoic). The results obtained indicate that effective osmoregulation in pink salmon during spawning migration from the sea to the river allows the implementation of a reproductive strategy.

The analysis of the relative level of expression of the genes of desaturases and elongases (fadsd5, fadsd6, elovl2, elovl5a), involved in the biosynthesis of long-chain polyunsaturated fatty acids, was carried out in the liver of juvenile Atlantic salmon Salmo salar Linnaeus 1758, reared under differ-ent photoperiod and feeding regimes in aquaculture of the southern region.

The total lipid (TL) and fatty acid (FA) contents in tissues and body segments were studied in adult Antarctic krill (Euphausia superba) caught in three regions of the Atlantic sector of Antarctica with different environmental conditions. Significant differences in lipid and FA status of the Antarctic krill tissues and body segments were observed in the regions. Main metabolic indices indicating quality of lipids showed that E. superba has a high nutritional value. In particular, lipids are highly unsaturated in the species and ratios of physiologically significant and essential FAs are favorable to human health. This was assumed to be a distinctive biochemical characteristic of the species. Data from the study can be used to form a scientifically based approach to further technological processing of raw krill and targeted extraction of certain substances and components of a lipid nature.

Activities of energy and carbohydrate metabolism enzymes (cytochrome c oxidase (COX), pyruvate kinase (PK), glucose 6-phosphate dehydrogenase (G6PD), glycerol 1-phosphate dehydrogenase (G1PDH), lactate dehydrogenase (LDH), and aldolase) were studied in rainbow trout Oncorhynchus mykiss Walb. fish grown in aquaculture in North Ossetia–Alania after introducing a regime with 24-h lighting and night feeding. COX and PK activities in the liver of fish from the experimental group were found to be significantly higher than in control fish, indicating an increase in aerobic ATP synthesis. Aldolase activity in organs of fish grown with 24-h lighting was lower than in the control fish, indicating a decrease in carbohydrate utilization in glycolysis in muscles and a lower intensity of gluconeogenesis in the liver. The differences made it possible to assume that the introduction of 24-h lighting and night feeding changed energy and carbohydrate metabolism to facilitate biosynthetic processes and, therefore, weight gain in fish.

Ulcerative dermal necrosis (UDN) in salmonids is a severe disease of mature salmonids characterized by abundant mortality of the infected fishes. The necrosis involves skin ulcers, which are further infected with secondary infections (for example, oomycetes of the Saprolegnia genus or various pathogenic bacteria) that ultimately leads to death. The disease named “salmon disease” was recorded in the 19th century; then it was noted periodically till the 1960s, when the infection was detected in southwestern Ireland, and afterward spread to the rivers of the British Isles and neighboring countries. Currently, the cases of outbreaks of mass salmon infection depend on the season and the region. In recent years, reports on increased sickness rate of salmonids have been received from a number of countries, including Sweden, Finland, Russia, and others. It is noted that only half of the fish with UDN-like lesions were specifically diagnosed as UDN on the basis of all diagnostic criteria of this disease. Considering this fact, and also taking into account the detection of new symptoms in infected fish, including red spots on the skin, a rash on the abdomen, skin bleeding, a new disease is revealed. This disease is called “Red Skin Disease” (RSD), and now it has its own diagnostic criteria as well as UDN. Recording of the new disease and approval of its name was carried out at a scientific seminar at the Norwegian Institute of Nature (NINA, Norway) in November 2019. Attempts to clarify the etiology of UDN have been made since the 1960s. Despite the fact that most researchers consider the nature of the disease to be viral, there is no clear scientific evidence for this. It is noted that there are extremely little convincing data about the origin, etiology, pathogenesis, and possible consequences of this dangerous disease, so it is necessary to expand comprehensive interdisciplinary research using modern experimental and communication methods. This will allow the development of effective measures to deal with this disease and propose a system for monitoring and predicting the future state of Atlantic salmon populations.

The general ideas regarding ecological biochemical adaptations in aquatic organisms are based on the results obtained by using a set of field and experimental methods over decades of research on members of marine and freshwater fish fauna and on their food items (mollusks, crustaceans) carried out by Science School in Ecological Biochemistry. Examples of biochemical adaptations in aquatic organisms are provided. Certain conclusions are drawn regarding the common and specific pattern of the metabolic adaptive response in the studied organisms growing and developing under normal conditions and upon changes in the environment. The results improve our understanding of the mechanisms behind ecological biochemical adaptations and their role in maintaining homeostasis in aquatic organisms.

A comparative study of the fatty acids composition in the feed and food lump from the rectum, and in muscles and internal fat of rainbow trout Parasalmo mykiss (Walbaum, 1792) grown on various diets in June and Septem-ber was carried out. Differences in content of dietary fatty acids in diet 1 and diet 2 were found. Monounsaturated fatty acids predominated in diet No. 1. A significantly higher level of saturated and ω3 polyunsaturated fatty acids in diet No. 2 was recorded. Concentration of ω6 polyunsaturated fatty acids in diets was equal. Despite the differences in the fatty acid composition of the diet, a decreased concentration of fatty acids in the intestines for the two groups of fish was similar and did not depend on the month of the study. Polyunsaturated fatty acids were absorbed more effectively in rainbow trout. Monounsaturated fatty acids showed a low level of assimilation. Significant differences in the content of saturated fatty acids in the food lump from the rectum and in feed was not stated. Monounsaturated fatty acids dominated in muscles and visceral fat of rainbow trout compared to other fatty acids. In June concentration of ω3 polyunsaturated fatty acids increased in the muscles of trout species of group No. 2 (143.9 ± 8.9 mg/g lipids), while concentration of monounsaturated fatty acids increased in the internal fat of the fish of group No. 1 (310.8 ± 10.8 mg/g lipids). This fact corresponded to the predominance of these classes of fatty acids in the feed of the fish. Concentration of mono- and polyunsaturated fatty acids in the tissues of the two groups of the fish increased by the end of the exper-iment. Monounsaturated fatty acids were mainly stored in the internal fat of trout, while polyunsaturated fatty acids were deposited in the muscles of the fish.

The effect of two light regimes, 16L:8D (16 h light : 8 h dark) and continuous (24 h light : 0 h dark), on the growth rates and gene expression level of myogenic regulatory factors (Myf5, MyoG, MyoD1a, MyoD1b, MyoD1c), myosin heavy chain (MyHC), and myostatin paralogs (MSTN1a and MSTN1b) in the muscles of Atlantic salmon yearlings reared for 3.5 months (from July to October) in the fish hatchery conditions were investigated. The control group consisted of salmon yearlings reared in the tanks of the same hatchery using standard technology without additional lighting. Despite the fact that there were no significant differences in body mass between the studied fish groups at the end of the experiment, additional lighting had a positive effect on the duration and intensity of fish growth in the autumn period with a decrease in water temperature. In autumn, the expression levels of the MyHC, MyoG, MyoD1, and MSTN1b paralogs were significantly higher in fish from the experimental groups with additional lighting compared to those in the control group. The revealed intergroup differences in the simultaneous expression of the studied genes indicate differences in the mechanisms of muscle growth regulation in fish depending on the lighting conditions. Patterns in the seasonal dynamics of genes’ expression levels that regulate muscle growth, which are similar for salmon yearlings’ groups kept under different lighting conditions, were established.

The article presents information about the formation and development of the leading science school in Ecological Biochemistry of Animals, which is primarily composed of research associates, graduate and post-graduate students of the Environmental Biochemistry Laboratory of IB KarRC RAS, representing several generations of researchers united by common scientific interests. Studies of the science school team are mostly concerned with the biochemical and molecular-genetic mechanisms behind the development of adaptive reactions in organisms of various ecological and phylogenetic groups. The article provides information on the main scientific results and publications of the science school team regarding ecological and biochemical adaptations of organisms, mainly aquatic ones. Examples of the biochemical adaptations in aquatic organisms are given.