Z. A. Nefedova

Lipid status and feeding habits of salmonid juveniles in the year preceding seaward migration as factors controlling their future smoltification

Juveniles of coho salmon Oncorhynchus kisutch (Walb.) and mykiss Parasalmo mykiss (Walbaum) of the same age (1+) become differentiated as early as eight months before smoltification and seaward migration by their lipid level, feeding habits, and size and weight parameters. It is found that juveniles of coho salmon and mykiss with a high lipid status have a greater (on average) length and weight and consume more calorific food items. The juveniles with a lower lipid status have a lower length and weight and consume less calorific organisms. It is presumed that a considerable part of juveniles with a high lipid status will migrate seaward next year. The role of the trophic factor in development of this differentiation and, accordingly, in determination of smoltification dates is discussed.

Dynamics of lipid content during early development of freshwater salmon Salmo salar L.

Dynamics of lipid and phospholipid content was studied during early development of freshwater salmon Salmo salar L. from blastodisc formation (3 h) to hatching (108 days) as well as in eggs before fertilization. High and stable content of total lipids including structural phospholipids as well as relatively high content of triglycerides and its slight increase at the time of hatching have been demonstrated, which can indicate their utilization as the main energy source after hatching under conditions of deficient food and low fry activity for some time. Accumulation of a certain level of lipids in eggs before spawning is required for embryonic development and high survival after hatching. The significance of increasing and decreasing levels of structural lipids modulating membrane enzyme activities in metabolic changes before hatching is discussed.

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.

Modifications of gill lipid composition in littoral and cultured blue mussels Mytilus edulis L. under the influence of ambient salinity

Changes of the lipid composition (mainly of membrane lipids) in gills in response to various seawater salinities were studied in two groups of mussels Mytilus edulis L. from the White Sea, living under different environmental conditions (intertidal zone and artificial substrates used in aquaculture). Modifications in the lipid composition involved the basic indices characteristic of the physical state of biological membranes, and minor components of the lipid bilayer, which perform regulatory functions, indicating that the lipid metabolism of the bivalves has undergone acclimation transformations in response to salinity. It is demonstrated that the response to critical salinity (5 ppt) in membrane lipids was similar in the two investigated groups of mussels, whereas with salinities of 15, 35, and 45 ppt the pattern of fluctuations in the lipid composition depended on the initial habitat (intertidal zone or aquaculture).

Lipid Status of the Two High Latitude Fish Species, Leptoclinus maculatus and Lumpenus fabricii

A comparative study of the lipid status (i.e., the total lipid and phospholipid concentrations and the percentage of fatty acids of the total lipids) of adult specimens of daubed shanny (Leptoclinus maculatus) from Svalbard waters (Isfjord) and slender eel blenny (Lumpenus fabricii) from the White Sea (Onega Bay and Tersky shore) was performed to study the metabolism and functions of lipids of these fishes in ontogeny and under various ecological conditions. Slender eel blenny from both areas of the White Sea were distinguished by a high level of sphingomyelin compared with the daubed shanny from Svalbard, and the amount of total phospholipids was higher in slender eel blenny from Onega Bay than in slender eel blenny from the Tersky shore. The extent of saturation and the signature of polyenic fatty acids varied according to the specific species of the Stichaeidae family under study. These results demonstrate the differences in the trophoecological and hydrobiological conditions of habitations of these species and highlighted the importance of considering certain trends in the lipid profiles of these fishes as specific features of the organization of the ecological and biochemical mechanisms of adaptation.

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.

The lipid status of young of the year mykiss Parasalmo mykiss and coho salmon Oncorhynchus kisutch

The young of the year mykiss Parasalmo mykiss and coho salmon Oncorhynchus kisutch which perform downstream migration and which stay in the coastal zone during the period of primary dispersion represent different phenotypic groups. They differ in weight, length, and lipid status. Such differentiation is a factor controlling the formation of intrapopulation diversity and of the life strategy of fish. It may determine the timing of smoltification in the future and, further on, of the return for spawning. There were found some analogies and differences in characteristics of lipid metabolism in the investigated species. The content of total lipids decreases by autumn in underyearlings of both species. Furthermore, changes in the content of particular lipid fractions are multidirectional and various scaled, seemingly being related to physiological preparation for the wintering.

Modulating role of lipids and their fatty acids in adaptation of the White Sea mussels Mytilus edulis L. to environmental salinity change

Role of lipids and fatty acids (FA) in littoral and sublittoral White Sea mussels Mytilus edulis L. was studied at various stages of reproductive cycle in the phenotypic adaptation (acclimation) to changes of the sea water salinity. The obtained data indicate differences in the mussel lipid and fatty acid spectra, which are connected both with their location (littoral or sublittoral) and with the spawning period stage (3b—release of gametes or 3c—resorption of residual sex products). Lipids and FA of both mussel groups respond to the salinity changes to the greater degree at the 3b than at the 3c stage. In the littoral mussels at the 3b and 3c stages there were revealed differently directed changes in the content of membrane lipid—cholesterol—and in the cholesterol: phospholipids ratio. In the sublittoral mussels that are less adapted to extreme action of abiotic factors, more significant changes were found in the lipid and FA compositions.

Lipid status of larvae and adults of the White Sea herring Clupea pallasii marisalbi Berg (Clupeiformes, Clupeidae)

37 The population of the White Sea herring Clupea pallasii marisalbi Berg (Clupeiformes, Clupeidae) is one of the closest forms of the Pacific herring and one of the most important commercially valuable fishes of the White Sea. The growth of the herring stock in recent years is due to its gradual recovery (after the death in the early 1960s) of the White Sea eelgrass, whose thickets serve as spawning and development sites of eggs as well as foraging and growth sites of her ring larvae and fries [1]. Biochemical studies on the White Sea herring are practically absent. However, such studies could help answer the question as to whether different groups of herring are characterized by biochemical heterogeneity. It is known that lipids play an important role in the formation of the bio chemical status of organisms. They are essential struc tural components of biological membranes, are involved in energy processes in cells and in the regula tion of biochemical reactions and physiological pro cesses, are the precursors of the biosynthesis of steroid hormones, etc. [2, 7].