A. E. Veselov

Age Dynamics of Lipid Status of Juveniles of Atlantic Salmon (Salmo salar L.) from the Varzuga River

Heterogeneity of zero class (0+) of Atlantic Salmon Salmo salar from the compared biotopes of the Varzuga R. (the Kola Peninsula) is revealed by the content of TAG, PL, 18:2n-6,18:3n-3, the sum of monoenoic FA, and parameters of CS/PL and TAG/PL retained in elder age groups of parr (1+ and 2+). It depends on the quality of food resources and hydrological conditions. The increase in the level of PS, one of the principal regulators of activity of Na+/K+-ATPase—a key enzyme of osmoregulation—in parrs 1+ and, to a greater extent, in smolts is supposed to be the formation of one of the biochemical mechanisms of preadaptation of fish to a marine environment. Salmon juveniles 3+ differ from the fish of junior age groups in a higher content of PUFA (20:4n-6, 20:5n-3, 22:6n-3), a considerable decrease in TAG, in parameter TAG/PL, and the sum of monoenoic FA related to smoltification and preparation for life in a marine environment. Multidirectional variations of concentrations of minor phospholipids (PI, LPC, SPM) in salmon juveniles depending on age and habitat may indicate the change in viscosity of biomembranes and, accordingly, of activity of some enzymes bound with membranes.

The effect of environmental conditions on the dynamics of fatty acids in juveniles of the Atlantic salmon (Salmo salar L.)

The dynamics of fatty acid composition have been studied in differently aged salmon juveniles (0+, 1+, 2+ parrs and 3+ smolts) inhabiting two biotopes of the Varzuga River (the White Sea basin) differing in ecological conditions. Differences in the levels of linoleic (18:2n-6), linolenic (18:3n-3), and oleic (18:1n-9) acids have been revealed. It has also been shown that 3+ smolts have an increased content of long-chain fatty acids—arachidonic (20:4n-6), eicosapentaenoic (20:5n-3), and docosahexaenoic (22:6n-3)—characteristic of the composition of marine-type lipids.

Parameters of energy metabolism in juveniles of Atlantic salmon Salmo salar living in the mainstream and in the tributary of the Varzuga River (the Kola Peninsula)

In juveniles of Atlantic salmon Salmo salar of two age groups (0+ and 1+) living in the mainstream and in the tributary of the subarctic Varzuga River, the activity of some enzymes was determined (cytochrome c oxidase, malate dehydrogenase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, and 1-glycerophosphate dehydrogenase), reflecting the intensity of the direction of principal pathways of carbohydrate metabolism and of synthesis of ATP. The effect of environmental conditions on growth and development of different age groups is different. Underyearlings (0+) living in the tributary are characterized by an advanced locomotor performance and growth rate. They possess a higher level of aerobic and anaerobic energy metabolism and assimilation of carbohydrates for synthesis of structural and stock compounds in comparison with yearlings living in the mainstream. No significant differences are found between two-summer-old fish (1+) from different habitats in parameters of energy metabolism. This demonstrates that the living conditions for them in the tributary are not so favorable as from underyearlings. The food items in the tributary are small and numerous, i.e., are more available for salmon underyearlings. Parrs 1+ feed on large invertebrates and feeding in the mainstream is preferable. The differences in parameters of energy metabolism of juvenile salmon manifesting themselves in the first year of life make the basis for the fact that the subsequent smoltification of parrs and migration for feeding occur at different ages—2+, 3+, or 4+. This contributes to the formation of the complex age structure of the Varzuga stock of salmon.

Lipid status of fingerlings of the Atlantic salmon Salmo salar from different microbiotopes of the Varzuga River

Mechanisms of formation of phenotypic groups of fingerlings of the Atlantic salmon are investigated, related to diversity of embryos and subsequent start possibilities of dispersion of larvae to microbiotopes differing in their life conditions. The fingerlings of salmon, which after hatching and dissolution of the yolk sac moved from the mainstream of the Varzuga River to mouths of its tributaries, had an increased level of triacylglycerols and a higher growth rate than the juveniles remaining in the coastal zone of the river. The revealed differences between the compared groups of fingerlings by the spectrum of stock and structural lipids are mainly connected with distinctions of feeding of juveniles of the same age. The found stable differences by lipid spectra in fingerlings of salmon from the investigated biotopes of the Varzuga in July, August, and October are considered as biochemical prerequisites of the origin of different phenotypic groups of juveniles. Subdivision of fingerlings into phenotypic groups may further on influence the oncoming of the smoltification time of juveniles at the age 2+, 3+, and 4+. Accordingly, this is reflected in formation of the complex age structure (by the number of years spent in the river and in the sea) of the Varzuga population of Atlantic salmon.

Intracellular protein degradation in the development of the atlantic salmon Salmo salar L.

Through the example of the Atlantic salmon Salmo salar L. we provide here the quick details on the universal and specific features of the proteolytic apparatus in the skeletal muscles of fish. Among the numerous muscle tissue proteases, the most comprehensively studied are those which determine the protein degradation levels in the efficiently growing and developing muscles of the salmon juveniles and by this way regulate the protein accumulation rates in muscles and the overall growth processes in the organism, namely, the lysosomal cathepsins B and D and calcium-dependent proteases (calpains). We have detected the age-related differences in the activity of the intracellullar proteases in salmon muscles, which suggest the important role of the proteolysis regulation in growth and the specific role for the certain proteolytic enzymes. For example, we have obtained data indicating the negative correlation between the cathepsin D and calpains activity levels in muscle tissue and the weight gain rate in the salmon of different age groups. The detected positive correlation between the cathepsin B activity and the morphometric indices in juvenile fish is apparently indicative of the key role of this enzyme in the metabolism of proteins of the predominantly nonmyofibrillar nature.

Rheoreaction as a mechanism of formation of phenotypic groups of underyearlings of the Atlantic salmon Salmo salar

Experimental investigation on rheoreaction as a behavioral mechanism in the formation of phenotypic groups of underyearlings of the Atlantic salmon Salmo salar is performed. Juveniles of the Atlantic salmon are investigated at the age 0+ from the coastal group and from the tributary group in the period of its primary distribution from redds. The underyearlings from the tributary group differ from the coastal fish in increased critical current velocity, the fact that among them the most portion of individuals have a positive type of rheoreacrtion, and the fact that they prefer currents more often. The behavioral mechanism of spatial separation of the spreading juveniles at confluence of two currents is revealed: stronger individuals with the positive type of rheoreaction and the expressed rheopreferendum mainly move against the flow at a higher speed and manage to get into a tributary. The weaker fish with static and negative dynamic types of rheoreaction, having no expressed rheopreferendum, prefer the flow with lower current rate and turn out to be in the coastal zone of the mainstream.

Heterogeneity of lipids and fatty acids of fingerlings of Atlantic salmon Salmo salar L. different in weight and size

Lipid and fatty acid spectra have been investigated in fingerlings of Atlantic salmon distinguished by weight and length characteristics and degree of fatness. Heterogeneity in terms of fatty acids in the studied groups of fingerlings is shown which indicates the differences in the rates of biochemical reactions of synthesis and modification of lipids and fatty acids caused by phenotypic diversity. Specificities of the metabolic processes in the studied groups of salmon fingerlings are related to the qualitative variety of nutrition spectra and the availability of food in the biotope.

Activity of metabolic enzymes and muscle-specific gene expression in parr and smolts Atlantic salmon Salmo salar L. of different age groups

This study was conducted to characterize the energy metabolism level and the features of muscle growth regulation during the development of Atlantic salmon (Salmo salar) inhabiting the Indera River (Kola Peninsula, Russia). The activities of aerobic and anaerobic enzymes (cytochrome c oxidase and lactate dehydrogenase) and carbohydrate metabolism enzymes (glucose-6-phosphate dehydrogenase, glycerol-3-phosphate dehydrogenase, and aldolase) were measured in muscle and liver tissue. Gene expression levels of myosin heavy chain (MyHC), myostatin (MSTN-1a), and myogenic regulatory factors (MRFs—MyoD1a, MyoD1b, MyoD1c, Myf5, myogenin) were measured in the white muscles of salmon parr of ages 0+, 1+, 2+, and 3+ and smolts of ages 2+ and 3+. Multidirectional changes in the activity of enzymes involved in aerobic and anaerobic energy metabolism with age were shown in the white muscles of the parr. The cytochrome c oxidase activity was higher in muscles of underyearlings (0+) and yearlings (1+) and decreased in 2+ and 3+ age groups. The activity of lactate dehydrogenase, in contrast, increased with age. The patterns of changes in expression levels of MyoD1a, MyoD1b, myogenin, MyHC, and MSTN-1a at different ages of the parr were similar. Particularly, the expression of these genes peaked in the yearling parr (1+) and then decreased in elder groups. The differences were revealed in parameters studied between the parr and smolts. The level of aerobic and anaerobic metabolism enzyme activities was higher in the white muscles of smolts than in parr. The activity of carbohydrate metabolism enzymes was decreased in the smolts’ livers. The expression levels of MyHC, MyoD1a, MyoD1b, and myogenin were lower in smolts at age 2+ compared to parr. These findings expand our knowledge of age-related and stage-related features of energy metabolism and muscle development regulation in young Atlantic salmon in their natural habitat. The results might be used for monitoring of the salmon population during restoration and rearing.

Activities of cytochrome c oxidase and mitochondrial lactate dehydrogenase isozymes and Cox1, Cox2, Cox4, and Cox6 gene subunit expression in cold adaptation of Salmo trutta L.

Characteristic changes in some parameters of white muscle mitochondria (mitochondrial volume, activity of cytochrome c oxidase (COX, EC 1.9.3.1) and the level of Cox1, Cox2, Cox4, and Cox6 subunit gene expression and activity and kinetic characteristics of mitochondrial lactate dehydrogenase isozymes (mtLDH, EC 1.1.1.27)) in adaptation to seasonal decrease in temperature from 16 to 6°C of one-year juvenile brown trout Salmo trutta L. from rivers of Lake Onega basin were investigated. A 1.5-fold increase in the activity of COX, and the increase in the levels of gene expression of both Cox4 and Cox6 nuclear subunits and increased activity of mitochondrial LDH isozymes, which have a low affinity towards lactate, has been shown. The possible role of nuclear and mitochondrial subunits of cytochrome c oxidase in improving the efficiency of the enzyme in molecule biogenesis and further modulation of its activity, as well as regulation of pyruvate formation to maintain the required rate of oxidative phosphorylation in mitochondria under low temperature were discussed.

The ecology of the freshwater form of the Atlantic salmon Salmo salar L., the brown trout Salmo trutta L., and the freshwater pearl mussel Margaritifera margaritifera L. in Syuskyuyanyoki River (Basin of Lake Ladoga)

The locations and the area of the spawning–growing grounds have been assessed in the Syuskyuyanyoki River (the basin of Lake Ladoga), as has the population density of the juveniles of the freshwater form of the Atlantic salmon and the brown trout. The Atlantic salmon spawns at present on the rapids downstream of the hydroelectric power plant because of the insurmountable dam; the population density of this species has decreased dramatically. Only the landlocked form of the brown trout was found; the anadromous form was not. The brown trout has resettled along the major part of the river. We suggest that there are two subpopulations of the freshwater pearl mussel that differ with regard to the host for their larvae. The intensity of invasion of the juveniles of salmonids by the larvae of the freshwater pearl mussel and the survivability of glochidia did not depend on the host species. The growth rate of the mollusks and the age–size structure of the freshwater pearl mussel population have been assessed.