Effect of different dietary levels of docosahexaenoic acid (DHA, 22:6ω-3) on the DHA composition of lipid classes in sea bass larvae eyes J.C. Navarro 1 *, L.A. McEvoy 2 , M.V. Bell 2 , F. Amat 1 , F. Hontoria 1 and J.R. Sargent 2 1 Instituto de Acuicultura de Torre de la Sal (CSIC), 12595 Ribera de Cabanes, (Castell ´ on) Spain 2 NERC Unit of Aquatic Biochemistry, Stirling University, Stirling FK9 4LA, Scotland, United Kingdom The effect of different dietary levels of docosahexaenoic acid (DHA, 22:6ω-3) on the corresponding composition of lipid classes of the eyes of sea bass, Dicentrarchus labrax, larvae was studied using Artemia nauplii enriched with different products: oil emulsions, liposomes, a dry microalga and baker’s yeast. DHA was found to be a major constituent of phosphatidylserine and phosphatidylethanolamine of visual tissues. The different DHA dietary levels were markedly reflected in the fatty acid composition of the lipid classes of eyes, suggesting a dose-dependent relationship between DHA in the food and in visual tissue lipids of sea bass larvae. The possible implications of this dietary effect are discussed. KEYWORDS: DHA (22:6ω-3), Eye lipids, Larvae, Sea bass, (Dicentrarchus labrax) INTRODUCTION Artemia nauplii lack long-chain polyunsaturated fatty acids (PUFA) essential for marine fish and crustacean larvae, and need to be supplemented, i.e. enriched, with these fatty acids. The enrichment process involves the incubation of the nauplii in media containing PUFA in the form of microparticles, yeast, algae, or, more often, emulsions (Watanabe et al., 1982). The nauplii are passive filter feeders that store the enrichment products in their digestive tract, thus offering the possibility of producing live diets containing different levels of essential fatty acids, and facilitating the study of nutritional effects in larval fish (Izquierdo et al., 1989; Koven, 1991; Navarro et al., 1993, 1995). Docosahexaenoic acid (DHA, 22:6ω-3) is very abundant in lipids from neural and visual tissue (Bell and Tocher, 1989; Bell and Dick, 1991) and is avidly retained in vertebrates in general (Anderson et al., 1990; Bazan and Scott, 1990). Thus the lipid composition of neural tissue may be a good indicator of nutritional deficiencies. Navarro et al. (1993b, 1995) have already described dietary influences of ω-3 PUFA in the fatty acid lipid class composition of *Author to whom correspondence should be addressed (e-mail: jcnavarro@iats.csic.es). 0967–6120 © 1997 Chapman & Hall Aquaculture International 5, 509–516 (1997)