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 an d C20 PUFAs were investigated in juvenile gilthead sea bream, Sparus a urata. The results indicate that juvenile gilthead sea bream have only limited ability to convert C18 PUFAs to C20 and C22 HUFAs in vivo. Th e data are consistent with the results from nutritional studies on lar vae, post-larvae and fingerlings that have shown that gilthead sea bre am require the provision of preformed eicosapentaenoic and docosahexae noic acids in the diet. The impairment in the desaturase/elongase path way was quantitatively and qualitatively similar to that found in turb ot, Scophthalmus maximus, being at the level of the DELTA5-desaturase. The low activity of DELTA5-desaturase combined with the consistent fi nding that arachidonic acid is selectively retained in membrane phosph atidylinositol suggests that, in addition to eicosapentaenoic and doco sahexaenoic acids, gilthead sea bream may also have a requirement for preformed arachidonic acid in the diet.