鲇仔、稚鱼消化系统胚后发育的组织学观察研究

通过石蜡包埋切片法对鲇(SilurusasotusL.)仔、稚鱼消化系统胚后发育进行了较系统的组织切片观察。本研究描述了全长5.0～22.5mm的鲇摄食器官、消化器官胚后发育的组织学结构特征。观察发现,1～3日龄为内源性营养阶段,卵黄囊很大,2日龄消化道出现裂缝状腔隙,3日龄基本贯通但未开始摄食;4～6日龄为混合营养阶段,卵黄囊被逐步吸收,主要靠吞食轮虫、小型枝角类等为食;6日龄以后卵黄囊消失,进入外源性营养阶段,捕食能力增强。观察还发现,鲇前咽顶壁始终平直无粘膜皱褶;颌齿和咽齿为斜生尖锥状的同型齿,数量多、排列紧密,与相应的骨骼牢固地骨性固着;后咽、食道的粘膜上皮内粘液细胞极多,深层结缔组织肌肉层发达。这些构造适应于鲇的完全吞食摄食方式。胃腔小,前肠膨大、中肠粘膜上皮细胞纹状缘发达,肝脏和胰脏发育速度较快。胃的消化功能较弱,主要储存、消化场所为前肠,吸收场所在中肠。鱼苗4～6日龄下塘适宜,6～8日龄可开始诱其摄食人工饲料。

Histological studies on post-embryonic development of digestive system in larval catfish Silurus asotus

Silurus asotus L. is widely distributed in China, but no study was reported on its digestive system during post-embryonic development in terms of histology. The paper illustrated the post-embryonic developmental histology of digestive system in catfish Silurus asotus L. by means of paraffinsection. The histological characteristics of feeding organ and digestive organ were described in larvae at 5.0-22.5 mm in total length. In 3 days after hatching, the digestive duct in the larvae is formed but no food is intaken when the catfish is in endotrophic stage. In 4-6 days after hatching, the mixotrophic stage, the yolk is absorbed fairly well and the larvae begin to ingest food from the environment. From day six on, the yolk disappears gradually, and the fish have the ability of swallowing fry of other species and exdoerophic stage begins. The epithelium of prepharynx is always plane that no mucous fold is found. Jaw teeth and pharyngeal teeth are taper-like, combined with the bone firmly, and when catfish is catching other small fishes, both teeth can cooperate effectively. A large number of mucous cells exist in mucous epitheloum of postpharynx and oesophagus. Muscle under submucous layer is developed in postpharynx and oesophagus. All these histological features facilitate the feeding habit of swallowing. The taste buds are seldom in mucous epithlium of digestive duct. Gastric cavity is small. The forepart of intestine is inflated in volume. The mucous epithelium of middle intestine is very developed. Liver and pancreas grow fast. By observation, the main section for digesting is in anterior intestine, and the main section for absorbing is in middle intestine. In this paper, some comparison is also made between catfish and other species in distinct characteristics of digestive system.