Igor N. Bakhmet

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).

Effect of copper and cadmium ions on heart function and calpain activity in blue mussel Mytilus edulis

The heart rate and calpain activity of blue mussels Mytilus edulis from the sublittoral zone, exposed to different levels of water-borne copper and cadmium, was investigated in a long-term experiment. The content of cadmium and copper in the blue mussel was determined using flame and graphite Atomic absorption spectroscopy. The observed concentrations ranged from 2.5 to 89.1 μg/g dry weight for cadmium and from 6.1 to 51.0 μg/g dry weight for copper in the control and highest concentration, respectively. Initially, increase in cardiac activity in response to copper and Cadmium exposure was observed under all pollutant concentrations (5–250 and 10–500 μg/L, respectively). The calpain-like activity in gills and hepatopancreas of the mussels treated with metals changed in dose- and time-dependent manner: from a sharp rise at the 250 μg/L concentration of copper on the first day to a significant decrease under the effect of Cadmium in the concentration of 500 μg/L on the third day of the experiment. These results suggest that: (i) heart rate oscillation may reflect active adaptation of blue mussels to contamination and (ii) animals have different sensitivity to copper and Cadmium according to the role of the metals in the mussels’ life activity.

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.

Lipid composition in response to temperature changes in blue mussels Mytilus edulis L. from the White Sea

Alterations of membrane lipid composition (cholesterol, phospholipids and their fatty acids) in response to various temperature changes were studied in blue mussels Mytilus edulis L. from the White Sea. Lipid composition changes after acute temperature stress, especially a temperature drop, included a significant reduction of the membrane phospholipid content directly (1 h) after return to the initial temperature, which was presumably a consequence of a non-specific stress reaction in the mussels. A longer recovery period (24 h) as well as long-term temperature acclimation (14 days) induced changes in gill fatty acid composition (for instance, a rise in phospholipid unsaturated fatty acids under low temperature impact), indicating ‘homeoviscous adaptation’ to maintain the membranes in response to temperature fluctuations. Moreover, the gill cholesterol level in mussels varied especially at long-term temperature exposure.

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 …

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.