[Bounds of change in unsaturation index of fatty acid composition of phospholipids at adaptation of molluscs to biogenic and abiogenic factors of external medium].

Comparative study of fatty acid composition of total phospholipids, as well as of phosphatidylcholine and phosphatidylethanolamine from hepatopancreas and leg muscle was performed on several representatives of gasteropods (Gastropoda) molluscs and bivalve (Bivalvia) mussel (Mytilus edulus). The objects of our study were marine litorins (Littorina saxsatilis) adapted to different temperature conditions of White Sea and Barents Sea, freshwater lymnaea (Lymnaea stagnalis) infested by Trematoda and mussels from White Sea and Black Sea. It was shown that depending on the existence conditions of studied tissue or lipid, the maximal change is observed in the percentage of saturated acids (4-83 %), the percentage of unsaturated acids was less expressed (1-14 %) and the changes in unsaturation index (UI) did not exceed 20 % on average. It was supposed that observed quantitative bounds of UI change under the action of different external factors is utmost for maintenance of membrane fluidity necessary for normal vital activity of cell, particularly in studied ectothermic molluscs.