CHARACTERISTICS OF THE MORPHOLOGY AND HISTOLOGY OF DIGESTIVE TRACT OF TRIPLOPHYSA TIBETANA, TRIPLOPHYSA STENURA AND TRIPLOPHYSA STEWARTI

The study investigated the atomical and histological structures of the digestive tract of T. tibetana, T. stenura and T. stewarti, and found that the digestive tracts of three species fish were composed of oropharyngeal cavity, esophagus, stomach and intestine. All of them were " U” type stomach without pyloric caecum. The short intestines could be divided into three parts of foregut, midgut and hindgut. T. stewarti had the largest stomach length and digestive tract length ratio (SL/DL) but with the shortest intestine length and standard body length ratio (IL/DL) that was significantly difference with the other two species (P<0.5). The average intestinal coefficients ofT. tibetana, T. stenura and T. stewarti were 0.64±0.08, 0.70±0.06 and 0.51±0.07, respectively. Thickness of mucosa and muscle in stomach of T. stewartiwas were the greatest. Thickness of mucosa in foregut of T. stewarti was the highest, meanwhile, thickness of muscle in foregut of T. tibetana was the highest. Thickness of mucosa in midgut and hindgut of T. stewarti was the largest, following by T. stenura and T. tibetana. Overall, the digestive tract structures and characteristics of three species of fish indicate that they should be carnivorous fish.