锯缘青蟹卵黄发生期卵巢和肝胰腺脂类的变化

Changes in lipid class and fatty acid compositions in the ovaries and hepatopancreas of the mud crab Scylla serrata during the vitellogensis of the second ovarian maturation

锯缘青蟹 2次卵巢发育时的卵黄发生旺期与卵黄发生初期相比 ,卵巢指数和卵巢脂肪含量 (%卵巢干重或湿重 )均显著增加 ,积累了大量的脂类 ,而这一时期的肝胰腺指数和肝胰腺脂肪含量均无显著变化 ,说明在卵黄发生时期 ,肝胰腺吸收的脂肪均及时转运到正在发育的卵巢 .卵黄发生期 ,卵巢或肝胰腺磷脂 /总脂的百分含量 ,均无显著变化 ,肝胰腺中游离脂肪酸逐步增加 ,甚至在卵黄发生后期超过甘油三酯的含量 .卵黄发生阶段 ,无论肝胰腺或卵巢 ,其磷脂长链多不饱和脂肪酸显著高于中性脂 ,而饱和脂肪酸含量相对较低 ;肝胰腺脂类脂肪酸组成的最主要变化是中性脂的n3系列的长链多不饱和脂肪酸 ,尤其是C2 2∶6n3显著降低 .卵黄发生初期 ,肝胰腺磷脂与卵巢中性脂的脂肪酸组成 (肝胰腺转运脂肪时 ,首先要将吸收或储存的脂类转换成磷脂 ,才能运出 )无显著差异 ,但卵黄发生旺期 ,肝胰腺磷脂的长链多不饱和脂肪酸显著高于卵巢中性脂的含量 .文中讨论了这些变化的原因 .

From the first vitellogensis to the second vitellogensis, total lipid contents(mg/g body wet weight ) and lipid concentration (% wet or dry ovarian weight) of the ovary, are significantly increased (P<0,05), and the neutral lipids(NL) and polar lipids(PL) occupy all increased total lipids, and may mainly be from the diet source, because total lipid contents and lipid concentration of the hepatopancreas are no significant changes. NL [mainly triacylglycerils (TG), cholesterol and small amount of free fatty acids (FFA)] in ovaries is about 60% of total lipids,and PL (mainly phosphatidylcholine PC and phosphtidylethanolamine PE) is about 40%. During vitellogensis stages, polar lipid(mainly also PC and PE) concentration(% total lipids ) in hepatopancreas is more than 30%, and NL (mainly TG, FFA and small amout of cholsterol) is less than 70%, nevertheless,it is noteworthy that FFA content increased during the vitellogensis, and its content is even more than that of TG in late vitellogensis. In the ovary or hepatopancreas,major fatty acids are C16∶0,C16∶1, C18∶0, C18∶1,C20∶1,C20∶4,C20∶5 and C22∶5,however, PL contains larger amount of long-chain polyunsaturated fatty acids (L-PUFA),such as C20∶4,C20∶5 and C22∶6 than that of NL. In the ovary, C20∶5 percentage decreases significantly and monounsaturate fatty acids increase significantly during the vitellogensis; in the hepatopancreas, the major changes of the fatty acids content are n3 L-PUFA, especially C22∶6 of NL decreases significantly during the vitellogensis. In the first vitellogensis,no significant difference is fond between the fatty acid content of PL(%PL) in hepatopancreas and that of NL in ovaries, indicating that lipid transported from hepatopancreas is mainly accamulated in NL; but in the second vitellogensis, L-PUFA content of NL (%NL), mainly C20∶4 and C20∶5 is much less than that of PL in hepatopancreas, this fact sugests that the large amount of phospholipid in the ovary from the hepatopancres is selectively incorpoirated L-PUFA of lipid into the lipovitellin at the expence of the decreace of these fatty acids of NL.