Decreased 20:4n-6/20:5n-3 ratio in sperm from cultured sea bass, Dicentrarchus labrax, broodstock compared with wild fish

The fatty acid composition of the four main phospholipid classes, phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphatidylinositol (PI), from the sperm of broodstock sea bass fed either a commercial pelleted diet or fed 'trash fish' were compared with sperm from wild fish. The phospholipids were very unsaturated, with total polyunsaturated fatty acids (PUFA) accounting for 35% of PC, 60% of PE, 85% of PS and 43-51% of PI. Docosahexaenoic acid was the major PUFA in PC, PE and PS, and arachidonic acid in PI. The fatty acids from the wild fish and broodstock fed 'trash fish' were generally very similar, but the fish fed a commercial diet had elevated 20:5n - 3 and decreased 20;4n - 6 reflecting the fish oil component of the diet. Consequently, ratios of 20:4n - 6/20:5n - 3 were greatly decreased in the phospholipids of fish reared on the commercial diet, especially in PI, where the ratio fell from 7.2 to 1.2. The possible functional consequences of these changes are discussed in relation to prostaglandin formation and egg and larval viability.