INCORPORATION AND METABOLISM OF C-14-LABELED POLYUNSATURATED FATTY-ACIDS IN JUVENILE GILTHEAD SEA BREAM SPARUS-AURATA L INVIVO

The incorporation, and the capacity for desaturation and elongation in vivo, of intraperitoneally-injected, C-14-labelled n-3 and n-6 C18 and C20 PUFAs were investigated in juvenile gilthead sea bream, Sparus aurata. The results indicate that juvenile gilthead sea bream have only limited ability to convert C18 PUFAs to C20 and C22 HUFAs in vivo. The data are consistent with the results from nutritional studies on larvae, post-larvae and fingerlings that have shown that gilthead sea bream require the provision of preformed eicosapentaenoic and docosahexaenoic acids in the diet. The impairment in the desaturase/elongase pathway was quantitatively and qualitatively similar to that found in turbot, Scophthalmus maximus, being at the level of the DELTA5-desaturase. The low activity of DELTA5-desaturase combined with the consistent finding that arachidonic acid is selectively retained in membrane phosphatidylinositol suggests that, in addition to eicosapentaenoic and docosahexaenoic acids, gilthead sea bream may also have a requirement for preformed arachidonic acid in the diet.