The association of eicosapentaenoic and docosahexaenoic acids in the main phospholipids of different-age Sparus aurata larvae with growth

Tissue fractions of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of 5-36-day-old Sparus aurata larvae, fed various levels of (n-3) highly unsaturated fatty acids (HUFA), were examined. Regression analyses were performed separately on eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels in these different phospholipids with larval growth as a means of evaluating their possible physiological value. PC and PE were the major phospholipid groups in larvae from this study. Their levels in fish were independent of diet although their composition was markedly influenced by the (n-3) HUFA content in the food they consumed. Larval phosphatidylcholine EPA/DHA ratios generally reflected those of the diet, suggesting that levels of assimilation of these essential fatty acids were similar. In contrast, the PE fraction, although a lesser constituent than PC, demonstrated the highest level (% of phospholipid) of (n-3) HUFA, mainly due to its selective incorporation of DHA. As a result there appears to be a relationship, independent of age, between the suggested patterns of EPA and DHA assimilation and growth. In the PC fraction, EPA and DHA were similarly incorporated and demonstrated high regression values (r² > 0.73). In contrast, DHA was preferentially assimilated into the PE fraction and was highly correlated with growth in 5-36-day-old larvae (0.77 and 0.80, respectively) while the EPA of PE was poorly associated with this parameter (0.24 and 0.27, respectively). The comparable or higher assimilation of DHA over EPA into the main larval phospholipids accompanied by good correlations with growth implies that DHA may have higher biological value in S. aurata larvae. In addition, the PE fraction may be particularly relevant in growth since there appears to be a higher assimilation of DHA into this phospholipid.