美洲黑石斑鱼(Centropristis striata)消化系统胚后发育的组织学观察

Histological Observation on Post-Embryonic Development of Digestive System of Centropristis striata

中文关键词: 美洲黑石斑鱼  仔鱼  消化系统  组织学

英文关键词: Centropristis striata  Larval  Digestive system  Histology

中文摘要:

      通过形态学与连续组织切片的方法，对美洲黑石斑鱼(Centropristis striata) 1–34 d仔鱼消化系统的胚后发育进行系统观察，分析描述鱼体消化道(食道、胃与肠道)以及消化腺(肝脏与胰腺)的发育过程。对1–15 d仔鱼连续取样，每次取样30尾，15 d后隔天取样，每次取样15尾。结果显示，在水温为(24±1)℃、盐度为30–32的条件下，初孵仔鱼卵黄囊体积很大，消化管为封闭的管状结构。美洲黑石斑鱼孵出3 d后，口裂形成、开始摄食，肛门与外界连通，消化道逐渐分化形成食道、胃及肠道，肝脏、胆囊和胰腺也逐渐形成。7 d后，卵黄囊与油球基本消失，食道、胃部以及肠道黏膜褶皱开始形成，消化道黏膜上皮细胞逐渐分化，肝脏出现脂肪颗粒，仔鱼具备了基本的摄食能力。11 d时，仔鱼食道可见黏液细胞，随日龄的增加上皮组织中黏液细胞数量迅速增多，褶皱日益丰富；胃部分化形成贲门部、胃本体与幽门部，胃壁褶皱不断增多、伸长；肝脏血窦与中央静脉明显。20 d时，鱼体胃腺形成，说明胃部消化、吸收蛋白质的能力增强；肠道次级黏膜褶皱出现，肠圈与褶皱更加复杂化；胰脏分布有大量酶原颗粒。32 d时，仔鱼消化道组织结构分明，自腔面向内依次为黏膜层、黏膜下层、肌层与浆膜层，消化道与消化腺结构和功能逐步完善。仔鱼3–7 d为内源性营养向外源性营养过渡期，应及时提供充足适口的生物饵料，仔鱼20 d后可以逐渐驯化投喂微型配合饲料。

英文摘要:

      The development of the digestive system of Centropristis striata and its associated glands were examined histologically from the first day (first day post-hatch, dph) until 34th day after hatching. Sampling was performed daily between 1 dph and 15 dph with sampling size around 30 fish. After that, sampling frequency was reduced to once every other day until 34 dph with sampling size of 15 fish. The newly-hatched larvae were reared in tanks with continuous supply of oxygen. Meanwhile salinity was about 30–32 and water temperature was maintained at (24±1)℃. It was found that the yolk sac of newly-hatched larvae was relatively large, while the digestive tract was a closed straight tube with a smooth lumen dorsally attached to the yolk sac. The mouth and anus formed and opened on the 3 dph, and followed by a 4-day period of mixed endogenous-exogenous feeding. Most of the yolk sac reserves were consumed rapidly; during this period, prey capture began and the digestive system continued to develop. Specifically, the digestive tract of larvae was differentiated into esophagus, stomach and intestine, and the digestive glands (1iver, gall-bladder and pancreas) began to form. Yolk sac and oil globule almost disappeared at 7 dph, and the nutritional requirements of the larvae has gradually made the transition from endogenous to exogenous. Mucous cells could be found in the epithelia of the oesophagus at 11dph, and the number of cells kept increasing during the larval development. Stomach was gradually differentiated into cardiacus, gastric body and pyloricus. At the same time, sinusoid and central veins of liver were clearly distinguishable. Gastric gland formed at 20 dph, which indicated the beginning of exogenous protein digestion. Increased wrinkles in the mucous layer and thicker muscles were detected in the intestine. Meanwhile, pancreas was abundant in zymogen granules spreading on the surrounding areas of the intestine. The structures and functions of digestive tract and digestive glands gradually became full-functional. It was concluded that C. striata larvae should be supplied with adequate and palatable food when they enter exogenous feeding period, and domesticated to feed formula feed after 20 dph. The findings on the development of the digestive system lead to a better understanding of the ontogeny of C. striata, which would be useful for improving the larval rearing techniques of this promising Centropristis species and therefore diversifying the freshwater aquaculture.