Comparative Study On Morphology And Histology Of Digestive Tract Of Three Species Of Triplophysa In The Yarlung Zangbo River

The Qinghai-Tibet Plateau had a special geographical environment and poor climatic conditions.Triplophysa was one of the dominant species of fish in the Qinghai-Tibet Plateau.There were few research on the digestive system of Triplophysa.The digestive system was not only an important place of the fish on food processing and utilization,but also the basis for growth and survival.In this study,the digestive tract structure of the three species of fish were studied by anatomy,light microscopy and electron microscopy,and compare the morphological and histological structures of them.This paper explores the characteristics of the structure and function,feeding habits and environmental impacts of the digestive system of the plateau,and aims to promote the basic biology,digestive physiology and nutrition and feed science of the genus Loach.In order to explore the structure different of the digestive tract of the three kinds of fish;to accumulate the basic biological data for the conservation and germplasm conservation of the Triplophysa.The experimental results are as follows:1.Morphology structure of digestive tractThe digestive tracts of three species of fish were composed of oropharyngeal cavity,esophagus,stomach and intestine.All of them were "U" type stomach.Besides,no pyloric caecum was found.These intestines were short and could be divided into three parts-foregut,midgut and hindgut.The mouth of T.orientalis was smaller and the oropharyngeal cavity length was longer.Intestinal of T.orientalis was short and curved two times,intestine length and standard body length ratio(IL/DL)was 0.64±0.08.Intestinal of T.orientalis curved four times,intestine length and standard body length ratio(IL/DL)was the maximum,0.70±0.059,which was significantly different from that of T.stewarti(P<0.05).The stomach length and digestive tract length ratio(SL/DL)of T.stewarti was the largest.Intestinal of T.stewarti was longest and curved two times,intestine length and standard body length ratio(IL/DL)was 0.64±0.08 and shortest.2.Histological structure of digestive tractThe basic histological structure of the digestive tract was consistent,from the inside out was divided into four layers: mucosa,submucosa,muscle,serosa.The esophageal surface of three kinds of fish distributed many large mucosal folds,mucosal epithelium was multilayer squamous epithelium mucosa and arranged Irregular.The boundaries between lamina propria and the submucosa of the three fish-specific were not significant,and the submucosa of T.orientalis had many longitudinal smooth muscle fibers.Esophageal muscle was striated.Circular muscle was inside and longitudinal muscle was outside.Serosa was thin,composed of mesothelial cells and connective tissue,and easy to fall off.The epithelium of stomach was a typical monolayer columnar epithelium,and no goblet cells.Only the cardiac and caeca stomach has gastric gland.Thickness of mucosa and muscle in stomach of T.stewarti was greatest.The forgut was with many strips of mucosal folds,rich in goblet cells.Submucosal for the loose connective tissue,showing chylous tubes,capillaries and so on.Thickness of mucosa of foregut of T.stewarti was the highest,meanwhile thickness of muscle of foregut of T.orientalis was the highest.he basic structure of the midgut was similar with the forgut.Thickness of mucosa in midgut and hindgut of T.stewarti was the largest,following by T.stenura and T.Orientalis.The anus for stratified squamous epithelium mucosa layer,and muscular layer consists of cyclic of muscle.