Lipid composition and vitamin content of wild female Litopenaeus vannamei in different stages of sexual maturation

Abstract

Wild Litopenaeus vannamei females in different stages of sexual maturation were sampled, including spent females and their nauplii, for determination of the lipid content, lipid class (LC) composition, fatty acid (FA) composition, vitamin C content and vitamin E content. Free FA (FFA), triacylglycerol (TAG), phosphatidylcholine (PC) and sterol esters (SE) were the dominant LC in the midgut gland. TAG and phospholipids (PL), mainly PC and phosphatidylethanolamine (PE), were the dominant ovarian LC. Neutral lipids (NL) prevailed over polar lipids (POL) in midgut gland lipids, while ovarian lipids displayed an inverse relationship. An increase in ovarian TL was observed from stage 0 (immature) to stage 1 (early maturing). Later, from stage 1 to stage 2 (mid maturing), a decrease in midgut gland TL was observed. TAG was most responsible for these changes in TL. Lipids were preferentially transferred to the nauplii, which contained relatively high TAG and PC levels. In both midgut gland and ovaries, 16:00, 18:00, 16:1 n−7, 18:1 n−9, arachidonic acid (ARA; 20:4 n−6), eicosapentaenoic acid (EPA; 20:5 n−3) and docosahexaenoic acid (DHA; 22:6 n−3) were the principal FA. All tissues and nauplii displayed n−3> n−6 and EPA>DHA relationships, and contained high proportions of n−3 highly unsaturated FA ( n−3 HUFA). During sexual maturation, the sum of poly-unsaturated FA (PUFA) decreased in the ovaries due to the decrease in n−6 PUFA such as ARA. The sum of mono-unsaturated FA (MUFA), on the other hand, increased in the ovaries. AA levels were high in immature, maturing and mature ovaries. They were low in the ovaries of spent females and nauplii. Vitamin E levels were low in immature ovaries, increased substantially during ovarian maturation, and then decreased again upon spawning. High vitamin E levels were retained in the nauplii. The findings of this study, combined with those reported in related studies, suggest the importance of n−3 HUFA for larval development, of vitamin C for egg development and hatching, and of vitamin E for ovarian maturation and larval development. These nutrients cannot be synthesised de novo by shrimp, and should be included at high levels in the broodstock diet.