Impact of algal diets and emulsions on the fatty acid composition and content of selected tissues of adult broodstock of the Chilean scallop Argopecten purpuratus (Lamarck, 1819)

The impact of dietary fatty acids on the fatty acid composition and content in different organs (digestive gland, adductor muscle and male and female gonad) of Argopecten purpuratus was evaluated during the process of gonad maturation under controlled laboratory conditions. A mixed algal diet of Isochrysis galbana (clone T-Iso), Pavlova lutheri, Chaetoceros gracilis and Tetraselmis suecica was either fed alone (Al) or supplemented with 50% lipids (expressed as % of the algal dry weight (DW)) using an emulsion rich in 22:6n - 3 (Al + EmDHA) or an emulsion rich in 20:5n - 3 (Al + EmEPA). Results showed the algal diet having the greatest impact on the fatty acid composition (mainly an increase of 18:1n - 9, 18:2n - 6; 18:3n - 3 and a decrease of 20:5n - 3) of the digestive gland and female gonad, moderate in the male gonad while the fatty acid composition of the adductor muscle was hardly affected. Our data indicated that 16:1n - 7 and 18:1n - 9 were partially elongated to 18:1n - 7 and 20:1n - 9, respectively. The supplementation of the algal diet with EmDHA or EmEPA (which contained 45% and 19% 22:6n - 3, respectively) increased significantly the concentration of 22:6n - 3 (mg g^-1 DW) in the digestive gland, female gonad and male gonad with 78%, 57% and 51%, respectively, for (Al + EmDHA)-fed scallops and 18%, 33% and 19%, respectively, for (Al + EmEPA)-fed scallops, while the 22:6n - 3 concentration in the adductor muscle was not affected. Broodstock conditioning was associated with a significant increase of the lipid content in the female and to a lesser extent in the male gonad. The significant increase (as compared to the initial sample) of the 22:6n - 3 concentration in the digestive gland, female gonad and eggs of A. purpuratus fed 22:6n - 3-rich lipid illustrated that recently ingested fatty acids did significantly contribute to the lipid accumulation process in the maturing female gonad. The similarities between the fatty acid composition of the female gonad and digestive gland suggest that lipids were transferred from the lipid-rich digestive gland to the female gonad.