Home – Home – Jornals – Contemporary Problems of Ecology 2018 number 3

The critical analysis of literature data on the distribution, morphology and phylogeography of the Pacific lamprey ( Lethenteron camtschaticum ) and five species of marine and anadromous fish such as navaga ( Eleginus nаvaga ), pollock ( Theragra chalcogramma ), Asian smelt ( Osmerus mordax dentex ), Pacific herring ( Clupea pallasii ), and pond smelt ( Hypomesus olidus ) has been performed. The results show that all these species colonized the North European seas, distributing along the Arctic coastline of Eurasia after the glacier retreat. The reasons which may impede the dispersal of these species in the Atlantic Ocean, such as preference for a cold environment, presence of competitors and decrease of the evolutionary potential, are discussed.

The features of the morphoecological and genetic polymorphism of whitefish ( Coregonus lavaretus L.) from the Keret’ River (White Sea basin) are discussed. According to morphological characteristics this whitefish population is homogeneous. At the same time, the differentiation with the lake whitefish populations of European Russia and Siberia was detected. The differences of the parameters associated with the movement and orientation of individuals in space (body height, length and position of the fins, interorbital distance) were revealed. For the first time the data of the craniological analysis were described for the White Sea whitefish. The results of the mitochondrial ND1 fragment polymorphism analysis confirmed the assumption of the heterogenous origin of the whitefish from the Keret’ River: the descendants of three different phylogenetic lines were found in the population.

We analyzed the partial sequences of the mitochondrial COI gene along with the amino acid sequences of the subunit I of cytochrome oxidase, encoded by this gene region, in representatives of 11 genera of salmonoid fish. For amino acid sequences, two alternative networks were constructed with outgroups represented by either Esocoidei or Osmeroidei as the supposed ancestral groups. In this way, Osmeroidei appear to be closer to the salmonoid fish than Esocoidei, and their presence in the network as an outgroup explains much better the available data on the morphology and karyology of salmonoids. A number of the results of this study are fundamentally new. In particular, slowing down of the molecular evolution of grayling (Thymallidae) is shown. We conclude that char ( Salvelinus ) is the closest to the ancestor modern genus of salmonoids. The hypothesis of the phylogenetic proximity of the genera Brachymystax, Hucho and Salmo has been confirmed. We also discuss the possibility of namely the changes in the amino acid sequence of the cytochrome oxidase subunit I may lead to postzigotic reproductive isolation between taxa.

The paper elucidates the features of colonization by whitefish ( Coregonus lavaretus L.) of water bodies of European Russia in connection with the Pleistocene glaciation events. Based on the data on the frequencies and phylogenetic relationships of mitochondrial DNA haplotypes, a significant role of migrants from the western periglacial refugia was shown. The first large refugium was located in the North Atlantic, and the other was placed in the South-East Baltic. Until the last glaciation, the maximum of which was observed about 20 thousand years ago, there were also migrations from Siberia. However, at present the descendants of these migrants in the water bodies of north-west Russia are not dominant. The size of the refugium may be an important condition for the successful spreading of the whitefish.

Two fish species, reared in aquaculture, pink salmon Oncorhynchus gorbuscha and whitefish Coregonus lavaretus , as well as ten species from natural habitats, whitefish C. lavaretus , tugun Coregonus tugun , broad whitefish Coregonus nasus , least cisco Coregonus sardinella , vendace Coregonus albula , boganid charr Salvelinus boganidae , charr Salvelinus alpinus complex, northern pike Esox lucius , sharp-snouted lenok Brachymystax lenok and taimen Hucho taimen were studied. The content of two long-chain polyunsaturated omega-3 fatty acids (PUFA), eicosapentaenoic (20:5n-3, EPA) and docosahexaenoic (22:6n-3, DHA) in muscle tissue of fish and in their food (intestine contents) was compared. In the aquacultures of whitefish and pink salmon, the content of the sum of EPA and DHA in food was significantly higher, than that in muscle tissue of the fish, which indicated losses of PUFA in the two-link food chain of aquaculture during their transfer to the upper trophic level. The losses of EPA and DHA in aquaculture, supported by numerous literature data, meant an inefficient usage of given sources of PUFA and an aggravation of a global deficit of these biochemicals in human diet. When studying natural fish populations, in many cases an accumulation of EPA and DHA in the biomass compared to the food was found, although contrary phenomena also took place. Basing on our and literature data, an existence of certain optimal physiologically adequate species-specific level of PUFA in fish muscle tissue was supposed. If a level of PUFA in the muscles was lower than the optimal one, their storing (bioaccumulation) from the food and/or de novo synthesis took place. In a case of exceeding the optimal level, the content of EPA and DHA in biomass approached to maximum species-specific values, but a part of these PUFA, obtained from food, either was not assimilated, or was catabolized. According to the data obtained, species from order Salmoniformes had the optimal level of 2-6 mg g-1 wet weight. As found, in aquaculture the approach to maximum values of EPA + DHA content was accompanied by their losses (scattering) in the food chains, while in natural ecosystems the maximum values of PUFA content in fish biomass were achieved by their accumulation from lower trophic levels. For boganid charr S. boganidae , the highest content of EPA + DHA in muscle tissue among all known fish species, 32.78 mg g-1 of wet weight, was recorded.

We studied the composition and content of fatty acids (FA) in the muscle, liver and reproductive tissues of males and females of perch from the Krasnoyarsk reservoir at the late stages of the reproductive cycle. The dynamics of the FA composition of perch muscle tissue was determined by a seasonal change in food sources composition, whereas the FA composition of the liver and gonad was influenced by the reproductive cycle and had differences between males and females. Multivariant analysis showed a redistribution of the FA between gonads and liver tissue. The nutritive value of perch muscle tissue, as a source of long-chain polyunsaturated fatty acids, did not depend on the reproductive stage.

No qualitative and quantitative differences in the profiles of fatty acids of their main groups between freshwater resident (the Orzega River, Onega Lake Basin) and anadromous (the Indera River, White Sea Basin) forms of young brown trout were found. The alterations in a rate of conversion of food derived 18:2ω-6 and 18:3ω-3 fatty acids into the long-chain and physiologically active - 20:4ω-6, arachidonic, and 22:6ω-3, docosahexaenoic, fatty acids were revealed. Freshwater residential young of brown trout (parr, at 3+ age) from the Orzega River were distinguished by higher index of 20:4ω-6/18:2ω-6. Anadromous form of the young of brown trout (smolts, at 4+ age) from the Indera River had higher ration of essential fatty acids - 22:6ω-3/18:3ω-3 and of polyunsaturated fatty acids - ω-3 to ω-6. The latter correlated with higher weight-length characteristics of the studied individuals.

A comparative analysis of lipid and fatty acids contents in certain portions of female gonads - front, central and tail - of prespawning pink salmon Oncorhynchus gorbusha was made. The heterogeneity of eggs was determined on the lipid status of certain portions of ovaries: in front portion - high level of physiologically important eicosapentaenoic 20:5 (n-3) and docosahexaenoic 22:6 (n-3) fatty acids, which coincided with higher intensity of lipid metabolism as evidenced higher ratio of 16:0/18:1(n-9); in central portion - low level of the general lipids due to phospholipids (including phosphatidylcholine, phosphatidylethanolamine, sphingomyelin) and cholesterol; and in tail portion - high amount of certain phospholipids (phosphatidylcholine, phosphatidylethanolamine, lysophosphatidylcholine, sphingomyelin, phosphatidylinositol). Heterogeneity found in certain portions of ovaries indicated asynchronism in biochemical processes in oocytes of these portions that might affect the ability of fertilization, growth and development of embryos and further differentiation of young fish.

Delayed maturation was observed in some diploid females reared in farming cages. Only males (fully mature and failing to mature) and intersexes were found among triploids. In this connection possible mechanisms of genetic sex determination in pink salmon as well as the possibility of using triploids for regulation of sizes of artificial pink salmon populations are discussed. A conclusion that use of triploids of pink salmon in aquaculture is unefficient has been made.