Hepatopancreatic contributions of lipids and carotenoids to vitellogenesis in the intertidal anomuran crab, Emerita asiatica (Milne Edwards)

Abstract

In decapod crustaceans, lipids and the associated carotenoid pigments form an integral part of yolk to serve as nutrients during embryogenesis. This study reports on the analysis of different lipid classes and the major carotenoids in the ovary, hepatopancreas and hemolymph and their fluctuation during different phases of ovarian maturation in an anomuran crab, Emerita asiatica. Neutral lipids including triglycerides (TG) and free fatty acids (FFA) formed the bulk of ovarian lipids. Important fatty acids are Saturated fatty acids (SFA) 16:0 and 18:0, Monounsaturated fatty acids (MUFA) 16:1n7 and 18:1n9, and Polyunsaturated fatty acids (PUFA) 20:5n3 and 22:6n3. While phospholipids increased during maturation, glycolipids decreased. Cholesterol level in ovary increased initially, but declined during later stages. Dominant pigments, β-carotene and astaxanthin, steadily increased during ovarian maturation within the ovary, although canthaxanthin declined drastically towards last stage. In hepatopancreas, however, TG and FFA showed gradual decrease during maturation. Palmitic acid, palmitoleic acid and eicosapentaenoic acid are the predominant fatty acids in hepatopancreas, showing a steady decline during ovarian maturation. Other lipid classes such as glycolipids also showed a decline in hepatopancreas. Both β-carotene and astaxanthin in hepatopancreas declined from the first stage of ovarian development, suggesting translocation to ovary. The overall metabolic changes of lipids and carotenoids in hepatopancreas, hemolymph and ovary are indicative of their accumulation within developing eggs to provide metabolic energy and substrates for membrane formation, and to serve as precursors for pigment formation respectively, during embryogenesis.