Lipid metabolism in destalked prawn Penaeus japonicus: Induced maturation and transfer of lipid reserves to the ovaries.

Abstract

Double tracer experiment using radioactive fatty acids was conducted in order to verify the transfer of lipid reserves to the ovaries during the ovarian maturation of the prawn Penaeus japonicus. The prawns were fed with a diet containing both palmitic acid (16:0)-3H and linolenic acid (18:3ω3)-14C, held for 1 day, and then maintained for 5 days with and without destalking. One day after feeding of the diet, both lipids-3H and lipids-14C were mainly distributed in the hepatopancreas as phosphatidylcholines (PC) and free fatty acids (FA) and in the muscle as PC. Bilateral destalk-ing resulted in the induction of ovarian maturation and also the increase in ovarian radioactive triglycerides (TG) and PC with a concomitant decrease in hepatopancreatic radioactive TG and PC. Thus, the destalking enhanced a transfer of body lipid reserves, particularly hepatopancreatic lipids, to the ovaries which accumulated TG and PC as the major lipid classes. From the 3H/14C ratios of ovarian PC and TG, it is likely that the major ovarian PC accumulated during the induced ovarian maturation are rich in ω3-fatty acids, possibly 18:30, 20:5ω3, 22:6ω3, etc., rather than 16:0 and its metabolites, whereas the major ovarian TG consist of 16:0 and its metabolites rather than ω3-fatty acids as acyl groups.