The Early Development Of Digestive System And The Activity Of Digestive Enzymes And Gene Expression In Percocypris Pingi

Percocypris Pingi is a fierce carnivorous fish peculiar to the upper reaches of the Yangtze River.In order to reveal the relationship between the morphological structure and function of the early digestive system,the early morphological development of the digestive system of 1-90 dah(days after hatching,dah)Percocypris Pingi was observed by histological method,and the activities of major digestive enzymes and gene expression patterns were studied by double antibody sandwich method and real-time fluorescence quantitative PCR.The main results are as follows:1、Under laboratory rearing conditions(water temperature 20.6±0.7 ℃),the intestinal morphological changes of Percocypris Pingi were observed.The results showed that the intestinal tract was undifferentiated when pectoral fin primordial phase(1 dah).The intestinal passage of the swim bladder(5 dah,total length:12.50±0.36mm),and the two fold points in the dorsal fin formation period(30dah,total length: 21.96±1.21mm)and the formation period of the hip fin(33 dah,total length: 23.56±1.33mm),and then "Z" form in the intestinal tract.There was no obvious change in morphology.In the course of intestinal development,the ratio of intestinal length/total length of Percocypris Pingi decreased at first and then increased.The ratio of intestinal length/total length of Percocypris Pingi was higher(0.50±0.04)before opening,and then gradually decreased to the lowest(0.39±0.03)until 25 dah.The ratio of the dorsal fin formation period(30 dah,0.41±0.03)gradually increased to 0.50±0.03(43dah),and the difference of the juvenile stage(46-90dah)ratio was not significant,mean reached0.53±0.15.Based on the ratio of length to length of the intestine and the ratio of all intestinal segments,the growth rate of the foregut,the posterior intestine and the total length was almost identical,and the growth rate of the midgut was faster than the total length,the foregut and the posterior intestine.2、The early development of digestive system of Percocypris pingi was observed by conventional paraffin tissue section and HE staining technique.The digestive system of the first hatched larvae was undifferentiated,and located on the back of the yolk sac.In the branchial period(3 dah,total length: 11.66±0.43mm),the buccopharynx begined to differentiate and the goblet cells and taste buds begined to appear,while the oesophagus,intestines,liver and pancreas also begined to differentiate.The goblet cells and the first fold in the oesophagus was appearanced at the swim bladder(5 dah,total length: 12.50±0.36mm),where the fold and the striate edge of the intestine begined to appear at this time.At one chamber air bladder stage(7 dah,total length:13.23±0.43mm),the larvae were fed,and goblet cells were found in the intestines.The buccopharynx and oesophagus were basically completed at two chamber air bladder stage(20 dah,total length: 16.87±1.07mm).The development of intestinal tract was basically completed at formation of dorsal fin stage(25 dah,total length:19.96±1.08mm).In addition,the development of liver and pancreas was completed at formation of ventral fin stage(37 dah,total length: 25.45±1.26mm).3、In this paper,the specific activity of trypsin,chymotrypsin,amylase and lipase in the early development stage of Percocypris pingi was analyzed by double antibody sandwich method.The results showed that the specific activity of trypsin,chymotrypsin,amylase and lipase were detected at hatching stage(1 dah,total length:9.94±0.54mm),indicating that the larvae and juveniles of the Percocypris pingi had the ability of initial digestion of live feed at 1 dah.The activity of trypsin,chymotrypsin,amylase and lipase increased first and then decreased,and the activity of amylase and lipase appeared at second fold points(33 dah,total length:23.56±1.33mm)in the intestinal tract,and the specific activity of trypsin and chymotrypsin was peak in the development of the tissue structure of the liver and pancreas(37 dah,total length: 25.45±1.26mm).4、The real-time expression of try,chy and amy of Percocypris pingi was analyzed by real-time fluorescence quantitative PCR at 1-90 dah.The results showed that the expression of try and chy increased first and then decreased,and reached the maximum at two chamber air bladder stage(15 dah,14.94±0.52mm).The expression of amy was stable before the opening(1-5 dah)at a high level(0.82±0.02),and then the expression of amy decreased gradually(90dah,0.73±0.02)until the end of the experiment.In conclusion,under the condition of laboratory feeding(water temperature20.6±0.7℃),the Percocypris pingi was in the formation period of the formation of anal fin stage(33 dah,total length: 23.59±1.33mm).When the two chamber air bladder stage(20 dah,total length: 16.87±1.07mm),the differentiation of the oropharynx cavity and esophagus was basically completed.the formation of dorsal fin stage(25 dah,total length: 19.96±1.08mm).the development of intestinal tract was basically completed.The development of the liver and pancreas was basically completed when the formation of ventral fin stage(37 dah,25.45±1.26mm).the specific activity of trypsin and chymotrypsin reached the peak at the formation of anal fin stage,and the specific activity of amylase and lipase reached the peak when the formation of ventral fin stage.the expression level of try and chy remained at a high level(1.43±0.02.1.26±0.02)during the formation of anal fin stage-the formation of ventral fin stage.Therefore,in the production practice,it was suggested that bait conversion could be done during this period.