半滑舌鳎消化系统器官发生的组织学

Histological study of the organogenesis of the digestive system of the tonguefish, Cynoglossus semilaevis

利用形态学和连续组织切片技术,对出膜后1～30d的半滑舌鳎消化系统胚后发育的组织形态学进行了系统观察和研究。研究表明,试验水温为20.0～22.0℃时,孵化后第3天,仔鱼开口摄食,消化道上皮细胞出现分化,肝脏和胰脏开始出现,鱼体开始由内源性营养转向外源性营养。孵化后第5天,卵黄囊完全被吸收,消化道明显分化成口咽腔、食道、胃、前肠和后肠,仔鱼消化系统具备了摄食和消化外源性食物的能力。此后随着鱼体的生长,粘膜层的褶皱增加,消化道上皮细胞进一步分化,肠道分段、盘旋,消化系统从功能和结构上逐步地完善成熟。开口摄食之后,先后发现在后肠出现嗜曙红颗粒,在前肠出现空泡,表明肠上皮细胞吸收了蛋白质和脂肪。继而糖元在肝脏中不断地储存。在出膜后第23天,出现胃腺,标志着稚鱼期的开始。

Histological changes of the digestive system and its associated glands were studied in tonguefish Cynoglossus semilaevis from the fast day （ fast day post-hatch dph） until 30 dph. Specimens for this study were hatched from artificially spawned broodstock and maintained in the indoor cement tanks （ 20.0 - 22.0℃ ）. At mouth opening （ 3 dph）, lengthening of the digestive tract, mucosae differentiation and pancreas and liver appearance were the most apparent elements. The yolk was gradually resorbed and disappeared on 5 dph., while the digestive tract was differentiated into five portions： buccal-pharyngeal cavity, esophagus, stomach, anterior and posterior intestine. The larval digestive system was morphologically ready to process external food at this time. During the following period of independent life the most noticeable events occurring were an increase in mucosal folding, cellular differentiation in the luminal epithelia, gut segmentation and looping. Thus, these digestive tract and associated glands became mature gradually and completed the morphological digestive features characteristic with increasing age and feeding activity. Glycogen was then progressively stored in the liver. Gastric glands were observed around 23d ph, which indicates the passage through the iuvenile oeriod.