Effect of broodstock diets on total lipids and fatty acid composition of larvae of gilthead sea bream (Sparus aurata L.) during yolksac stage.

Total lipid content and total lipid fatty acid compositions were studied in larvae at the yolksac stage of gilthead sea bream from two different broodstocks. The two broodstock diets had the same total lipid content but were different with respect to their fatty acid levels.There were differences in the fatty acid composition of total lipids in the two groups of larvae, reflecting the influence of fatty acid levels in the diets fed to the broodstock. The main fatty acids in both larvae lots during yolksac stage were 16:0, 18:1n-9 and 22:6n-3.The desaturation index Δx = [P + Σ (n - x) - Σ (n - x) diet]/P allowed the determination of the relative importance of the Δ9, Δ6, Δ5 and Δ4 desaturations during the egg and larval yolksac stages.The levels of total lipid fatty acids in eggs and larvae during yolksac period were almost constant and very low desaturation and elongation activities were apparent.A competitive inhibition was observed between the fatty acids of the n-6 series with respect to the ones of the n-3 series in those eggs and larvae from broodstock whose diet contained a high proportion of linoleic acid and its derivatives.