灰鲳仔稚鱼消化系统的发育

对出膜后1~35 d灰鲳仔稚鱼的消化系统进行了形态学和组织学观察。初孵仔鱼具有很大的卵黄囊,消化管为一简单的直形盲管。2日龄仔鱼消化系统中肠区首先开始分化,内面可见纹状缘。3日龄仔鱼胃区膨大,卵黄消失,肠道分化出小肠和直肠。侧囊在4日龄仔鱼时出现分化。5日龄仔鱼观察到幽门盲囊的初始结构,油球消失,从内源性营养向外源性营养过渡基本完成。6日龄仔鱼摄食主动。14日龄稚鱼肝脏分为两叶,体积增大,胰脏体积增大,胃弯曲呈"U"形,幽门盲囊指状分支已增加到几十个。22日龄稚鱼肠道弯曲更多,在胸腹腔中肠道盘曲程度已接近幼鱼。28日龄稚鱼侧囊背腹形成一纵隔,出现角质剌。35日龄稚鱼胃腺已十分丰富,侧囊结构也已完善,标志着灰鲳消化系统更趋完善。

Histological studies on development of digestive system in larval and juvenile dark pomfret(Pampus cinereus)

Morphological and histological studies have been made on the digestive system of dark pomfret (Pampus cinereus)from the first day to the 35 th day after being hatched.In newly hatched larva,yolk sac was large and the digestive tract was a straight diverticulum.The histological differentiation occurred first in mid-gut of DAH 2 larva,and striated borders also appeared on the free surface of epithelial cells of the mid-gut.On DAH 3,the stomach of larva inflated,yolk disappeared and intestine was differentiated into small intestine and rectum.The esophageal sac first appeared on DAH 4.The original structure of pyloric caeca could be observed,whereas fat ball disappeared,and the transition from endogenous nutrition to exogenous one was mostly finished on DAH 5.Larva began to ingest exogenous food on DAH 6.On the 14th day,the liver of juvenile fish was separated into two lobes.The volume of the liver and pancreas increased,while the stomach was twisted into "U"-like shape.and the number of the rami of the pylorie caeca increased to dozens.Intestine of the 22-day juvenile fish had more delete flexion,similar with that of young fish.The mediastinum and horny spine were observed in the esophageal sac of the 28-day juvenile.The powerful gastric gland and esophageal sac appeared in 35-day juvenile fish,suggesting that the structure and function of the digestive system of dark pomfret have been developed.