On Adaptative Changes of Rates of Oxygen Consumption and Lipid Metabolism in Littorina saxatilis at Parasitic Invasions

Abstract

Effects of parasites as a biotic factor on physiological and some biochemical characteristics of gastropod molluscs Littorina saxatilis are considered. The individuals infected at young age and incapable for reproduction due to parasitic castration have a lower intensity of respiration as compared with non-infected individuals of the same size. Large infected individuals that had time to realize their reproductive potential before pathological changes in hepatopancreas do not differ in respiration from the normal individuals. Comparative analysis of the lipid fraction of liver, particularly of the fatty acid (FA) composition of total lipids and phospholipids, allowed revealing essential differences between the control and infected individuals, as well as between infected individuals of different age groups. The absence of glycogen in the liver of infected L. saxatilis, which is revealed using thin-layer chromatography, indicates functional disturbances, including those in glycogen synthesis. We suggest that the reduction of intensity of metabolism in infected individuals is connected with peculiarities of digestive process at structural changes in the hepatopancreas damaged by sporocysts. In infected molluscs the FA composition relates mainly to parasite tissues than to the liver itself. In this connection, the role of lipids in regulation of enzyme activity and permeability of cell membranes is directed first of all to maintenance of parasite metabolism. The revealed elevated synthesis of stearic acid in infected individuals can be connected with its accumulation in parasite adipose cells. The FA composition of phospholipids in infected individuals had changes that can be directed to realization of barrier function of cell membranes, specifically to restriction of the rate of oxygen diffusion into sporocysts owing to condensation of membranes. Together with adaptive changes in FA composition the ratios saturated FA : unsaturated FA and ω3 : ω6 acids in control and infected individuals were preserved at the constant level, which in any case is connected with maintenance of normal functioning of cell membranes.