褐菖鲉仔、稚鱼消化系统发育的组织学观察

Histological studies on development of the digestive system in larval and juvenile Sebastiscus marmoratus

为探究卵胎生鱼类褐菖鲉(Sebastiscusmarmoratus)的仔、稚鱼消化系统组织学特点,采用常规组织切片技术,并用HE染色和组织化学染色,比较分析了产出后0～50d的褐菖鲉仔、稚鱼消化系统发育的组织学变化。结果显示:褐菖鲉初产仔鱼已分化出口咽腔,并具有初始的食道、胃、肠、肝脏和胰脏; 2日仔鱼肛门与外界相通,食道扩大,开始摄食,进入混合性营养期; 3～4日仔鱼幽门盲囊出现,食道内壁出现黏膜皱褶5～6个,胃黏膜皱褶5个,肝细胞团区域扩大; 5～6日仔鱼卵黄囊和油球耗尽,进入外源性营养期,食道黏膜上皮出现杯状细胞,肠道弯曲,可区分前中肠和后肠两部分;10～14日仔鱼食道环肌层明显,黏膜皱褶增加到7～12个,胃壁四层结构基本形成,肠道黏膜皱褶加深,纹状缘清晰可见,肝细胞分裂迅速,数量显著增加,体积增大,出现肝血窦和胰岛; 28～30日稚鱼出现胃腺和胃小凹,已具功能性胃,标志着稚鱼期的开始,此时胰岛细胞数量和酶原颗粒增多,消化能力显著提高;47～50日稚鱼已基本具有成鱼胃的特征,肠道纹状缘发达,肝细胞呈多边形,细胞内含大量脂肪颗粒,消化系统从结构和功能上已趋于完善。由此可见,褐菖鲉仔鱼和稚鱼消化系统的发育具有卵胎生鱼类发育较早的特点,与其消化功能的完善密切相关。

Sebastiscus marmoratus as a marine economical teleost, research on the development of the larvae and juveniles of this species become important. In this study, the developmental characteristics of digestive system in S. marmoratus from 0 to 50 days post-parturition (dpp) were described by the method of tissue sectioning technique, HE (hematoxylin-eosin) staining and histochemical staining. The results showed that the initial digestive system appeared to have a differentiated buccopharyngeal cavity after parturition. At 2 dpp, the larvae began feeding, and the digestive tube opened to the outside initially, and the larvae entered the endo-exotrophic period. The pyloric caeca appeared at 3?4 dpp, while 5~6 mucosal folds appeared in esophagus, and five mucosal folds appeared in stomach and hepatic cell mass grew. At 5?6 dpp, the yolk sac was completely absorbed, meaning the larvae began getting into exotrophic period Ⅰ(without a functional stomach). Meanwhile, goblet cells were observed in esophagus, and intestine can be divided into promesenteron and hindgut. At 10?14 dpp, circular layers of striated muscle were obviously observed and 7?12 mucosal folds appeared in esophagus;stomach had a basic structure, brush border became clear and there were a few hepatic sinusoids in a bigger liver, which was good for the digestion and absorption of exogenous food. At 28?30 dpp, the gastric glands and gastric pits appeared, which was the signs of the juvenile stage. With the increase of the number of islet cells and zymogen granules, the digestion was greatly improved. At 47?50 dpp, the digestive system gradually improved as a functional and structural one, which resembled that of adults. These results showed that the development of the digestive system in S. marmoratus started early like other ovoviviparous teleosts and was relative with the improving function of its digestion.