Natalia Fokina

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).

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.

Biochemical response of blue mussels Mytilus edulis L. from the white sea to rapid changes in ambient temperature

The effect of rapid changes in ambient temperature on the biochemical profile of the blue mussel, Mytilus edulis L., was studied under aquarian conditions. It was shown that modifications in the content of reserve and structural lipids and their fatty acids, activity of lysosomal enzymes (β-glycosidase, cathepsins B and D), cytosolic calcium-dependent proteases (calpains) and phase II enzymes of xenobiotic transformation (glutathione S-transferase) reflect a nonspecific compensatory response of bivalves to the stress-inducing effect of environmental factors and indicate a metabolic rearrangement which occurs in mussels within the first hours of temperature changes. High initial level of glutathione S-transferase activity in control mussels as well as elevation of glutathione concentration during experiment may promote favorable recovery of mussels from the hypometabolic state.

Role of lipids in adaptation of mussels Mytilus edulis L. of the White Sea to rapid changes in temperature

155 Bivalves Mytilus edulis L., as well as all inhabitants of the coastal sea area, possess adaptive features that allow them to withstand frequent fluctuations in abii otic environmental factors, including temperature, especially during the low tide [1, 2]. Taking into account the fact that lipids play a major role in the temperature adaptation of poikilothermic organisms [3], the purpose of this work was to study the compenn satory modifications at the level of lipid composition and expression of several genes of lipid metabolism in the gills of the White Sea mussels M. edulis in response to rapid changes in ambient temperature. Mussels were collected from the mariculture coll lectors in Kruglaya Bay (Kandalaksha Gulf, White Sea) at a depth of 1.5–2.0 m in April (0–3°C) and August (8°C) of 2012. Aquarium experiments to study the influence of temperatures were arranged on the basis of the Kartesh White Sea Biological Station of the Zoological Institute. The animals were acclimaa tized to the laboratory conditions for 72 h. Water temm perature corresponded to the temperature of natural water at the time of experiments and was 0–3 and 8°C. Then, the water temperature in the aquarium was increased from 0–3 to 8°C (in April) and reduced from 8 to 0–3°C (in August). Samples were collected after 11 and 244h exposure. Thereafter, the mussels were returned to the original temperature conditions: 0–3 and 8°C. Gill samples were taken for the bioo chemical and molecular analyzes (n = 5) 1, 24, and 72 h later. Water in the aquarium was aerated and changed daily, supplementary feeding was not perr formed. The composition of total lipids and individual phospholipid fractions and the fatty acid profile of phospholipids of M. edulis gills were studied by TLC, HPLC, and gassliquid chromatography, respectively [4–6]. The analysis of gene expression of proteins involved in lipid metabolism, such as Δ55, Δ66, and AM236589.2) was performed by realltime PCR in an iCycler thermocycler (BiooRad, United States). Gene expression level was calculated relative to the reference gene 28S rRNA (GB: Z29550.1) [7]. The significance of differences was assessed using the nonparametric Wilcoxon–Mann–Whitney test. Differences were considered significant at p ≤ 0.05 [8]. Seasonal features in the control groups of M. edulis studied manifested themselves mainly in the content of storage lipids triacylglycerols (TAG), the level of which was significantly higher in the gills of mussels collected in summer (table). It is known …

Does the membrane pacemaker theory of metabolism explain the size dependence of metabolic rate in marine mussels

ABSTRACT According to the membrane pacemaker theory of metabolism (MPT), allometric scaling of metabolic rate in animals is determined by the composition of cellular and mitochondrial membranes, which changes with body size in a predictable manner. MPT has been elaborated from interspecific comparisons in mammals. It projects that the degree of unsaturation of membrane phospholipids decreases in larger organisms, thereby lowering ion permeability of the membranes and making cellular, and thus whole-animal metabolism more efficient. Here, we tested the applicability of the MPT to a marine ectotherm, the mussel Mytilus edulis at the intraspecific level. We determined effects of body mass on whole-organism, tissue and cellular oxygen consumption rates, on heart rate, metabolic enzyme activities and on the lipid composition of membranes. In line with allometric patterns, the organismal functions and processes such as heart rate, whole-animal respiration rate and phospholipid contents showed a mass-dependent decline. However, the allometry of tissue and cellular respiration and activity of metabolic enzymes was poor; fatty acid unsaturation of membrane phospholipids of gill tissue was independent of animal size. It is thus conceivable that most of the metabolic allometry observed at the organismal level is determined by systemic functions. These whole-organism patterns may be supported by energy savings associated with growing cell size but not by structural changes in membranes. Overall, the set of processes contributing to metabolic allometry in ectotherms may differ from that operative in mammals and birds, with a reduced involvement of the mechanisms proposed by the MPT. Summary: The membrane pacemaker theory of metabolism applies only to systemic functions in the blue mussel Mytilus edulis.

Seasonal changes in lipid class content in mussels Mytilus spp. from Rakkfjorden in the Norwegian Sea and Kandalaksha Bay of the White Sea

The aim of the study was to increase knowledge regarding baseline biology of Arctic mussels (Mytilus spp.) in terms of lipid class content at different stages of reproductive development throughout the year. Lipid composition in the mantle and digestive glands were studied in mussels from the intertidal and subtidal zones of mussel beds located in the Norwegian Sea and the White Sea. Thin-layer chromatography was used to quantify phospholipids, triacylglycerols, sterols and their esters. The differences in climatic and hydrological conditions between the studied geographical locations of mussel beds were reflected not only in the timing and duration of the mussel’s reproductive stages, mainly active gametogenesis (stage II) and maturity (stage III), but also in the lipid composition of mussel mantle and digestive gland. The differences in environmental conditions between intertidal and subtidal zones of the studied mussel beds were also reflected in the lipid composition of mussels from both geographic locations, and determined the modifications of their lipid composition during the reproductive development. Although environmental conditions caused specificity in the distribution of the lipid composition in the mantle and digestive gland of Arctic Mytilus spp., the lipid composition variations that accompany the reproductive processes in bivalve mollusks were not affected.

Lipid Composition Modifications in the Blue Mussels (Mytilus edulis L.) from the White Sea

Studying biochemical indicators in response to various environmental factors allows revealing the metabolic adaptive strategy of the organism’s tolerance and survival under a variety of environmental impacts. This review analyses both the authors’ own data and the available literature on the problem of biochemical adaptations of the lipid composition in marine bivalves, particularly blue mussels, Mytilus edulis L., to various environmental impacts. Modifications in the composition of lipids and their fatty acids in blue mussels caused by short-term (under laboratory conditions) and chronic (field monitoring) exposure to natural and human factors indicate that homeostasis is maintained in cell membranes and the organism’s energy requirements and facilitate the adaptation and tolerance of the mussels to environmental disturbances. The lipid and fatty acid composition indices in White Sea intertidal mussels which reflect their chronic exposure to a wide variety of environmental factors are discussed and compared to data on changes in the lipid composition of blue mussels exposed to some environmental factors (salinity, anoxia, metals) in aquarium experiments. The lipid profile plays an important role in the adaptation of blue mussels to new conditions in the habitat, and it can be used as a biochemical marker for indicating the organism’s physiological state.