刀鲚幼鱼消化系统的组织形态学结构

采用光镜和扫描电镜观察长江刀鲚(Coilia nasus)幼鱼消化系统组织形态学结构。结果显示,刀鲚体长,口裂大,含有犬齿状的颌齿和尖锥状的腭齿,具有5对鳃弓,鳃耙长度明显大于鳃丝且表面附着不规则绒毛状细齿;胃呈"Y"型,胃与肠连接处具有16～21个指状环形幽门盲囊;肠为直肠,较短,比肠长为0.241±0.080;肝分为两叶,胰为独立的器官。刀鲚口咽腔为复层鳞状上皮,含有腺体、大量椭圆形黏液细胞、少量杯状细胞及味蕾;胃黏膜都为典型的单层柱状上皮,含有较多由上皮凹陷形成的胃小凹和胃腺;幽门盲囊具有20～25个丰富的褶皱,占满大部分幽门盲囊腔,黏膜层具有微绒毛;中肠黏膜上皮最发达,形成的褶皱细长且连接成网状,单层柱状上皮与复层扁平上皮交替分布。观察结果表明,刀鲚消化系统具有典型肉食性鱼类特征。

Morphology and Histology of the Digestive System in the Larvae of Coilia nasus

The morphology and histology of digestive system of Coilia nasus were studied using light microscopy and scanning electron microscopy. The digestive tract could be divided into the buccal-pharynx cavity, esophagus, stomach, intestine and anal portions. The specimen examined had a big mouth crack, canine-shaped jaw teeth, cone-shaped palatal teeth, but no pharyngeal teeth were observed. The specimen contained 5 pairs gill arch, and the length of gill raker whose surface being coated with irregular small tooth was greater than that of gill filament. The shape of stomach was like a "Y". 16-21 multi-finger pyloric caeca were observed in conjunctive site of the stomach and intestine. The intestine was short and rectum. The ratio of intestine length to body length was 0.241±0.080. Liver was divided into two parts. Histological studies showed that the wall of digestive tract was composed of mucosa, submucosa, muscle layer, and serosa layers. The mucosa epithelium of the buccal-pharynx cavity of this species was stratified squamous, with abundant rounded mucous cells. The taste buds, glands, and goblet cells were observed in the oral cavity. Mucosa epithelium of stomach was simple columnar, and well-developed gastric glands and gastric pits were present in the stomach. The pyloric caeca mucosa had about 20-25 wrinkles covered with microvilla, and these wrinkles filled in most part of the pyloric caeca cavity. The three portions of the intestine showed histological differences. Mucous epithelium of intermediate intestine was well developed, and both stratified squamous epithelium and simple columnar epithelium were observed. Mucosal foldings were slender and linked into a mesh. The results suggest that the digesting system of C. nasus shows typical characteristics of carnivorous fish.