九龙江口潮间带大弹涂鱼食性及其消化管组织结构

On feeding habits and histological structure of digestive tract of the mudskipper,Boleophthalmus pectinirostris,in intertidal zone of Jiulong River Estuary

本文对九龙江口北岸潮间带大弹涂鱼幼鱼和成鱼的食性作了周年分析,并观察了消化管的组织结构。大弹涂鱼所摄食的食物共有10个类群,其中生物类群至少有94种。主要摄食底栖硅藻和有机碎屑,系属植食性的底栖鱼类。个数百分比和出现频率百分组成较高的硅藻有布纹藻、菱形藻和舟形藻。摄食强度季节变化明显。体长42.4mm 以上,保持植食性不变,比肠长相对稳定。胃腺仅分布于贲门胃的粘膜层中,消化管的组织学特征与其食性相适应。

The present paper deals with the food composition,the seasonal variation of feeding intensity,and the relationship between the digestive tract and the feeding habits of mudskipper,Boleophthalmuspectinirostris.Mudskippers,young and adult(42.4～107.5mm in body length)were collectedmonthly in tidal mudflat of Haicang,Jiulong River Estuary,from September 1989 to August 1990.The results show that the herbivorous mudskipper feed on 10 groups of food items,among which ben-thic diatoms and organic detritus are important food for both the young and adult.The feeding intensi-ty varies with seasons obviously,the fullness coefficient of stomach and the percentage of stomachwith food are the highest in summer and the lowest during winter.The relative length of the intestine(the ratio of the intestine length to body length)is 1.35～1.43,the intestine in herbivorous mudskip-per is longer than in omnivorous or carnivorous fishes.The buccopharyngeal cavity,oesophagus,car-diac stomach,pyloric stomach,small intestine and rectum can be distinguished.Histologically,the di-gestive tract comprises four base layers——mucosa,submucosa,tunica muscularis and serosa.Thebuccopharyngeal cavity and the oesophagus are covered by stratified squamous epithelium containingmucus-secreting cells.In the I shaped stomach,the mucosa is constituted by simnple columnar epitheli-um.Simple tubular gastric glands are present in the cardiac stomach,but are completely missing in thepytoric stomach.The muscularis of the cardiac stomach is mainly composed of striated muscle fibres asin the oesophagus,whereas two smooth muscle fibres,the inner circular and the outer longitudinal,substitute the striated ones in the pyloric stomach and the intestine.The pyloric sphincter appears be-tween the pyloric stomach and the small intestine.The mucosa of the intestine consists of simplecolumnar epithelium intercalated with numerous goblet cells.The bile duct and the pancreatic ductlapped together externally by a common sheath of connective tissue,enter the anterior end of the smallintestine.A valve-like rectal sphincter marks the beginning of the rectum.The histological peculiari-ties of the digestive tract are adapted to its herbivorous habits.