| Schizopygopsis youughusbaudi Regan belongs to Cypriniformes,Cypriniidae,Schizothoracinae,Schizopygopsis,which is one of the Schizothoraxes endemic to China,It’s how to adapt to poor nutrition,low temperature,and strong ultraviolet rays are scientific issues in the course of its long-term evolution that deserve attention.However,the research about the adaptation mechanism of the Schizothorax to the nutritional utilization of bait in the plateau poor nutrition environment has not been reported.Therefore,a available bait was used to a bait-restricted simulation experiments,which only alter the number of feedings without changing the amount of each feeding.Our experiments aim to simulating that the fish’s encounter with insufficient of bait in the wild environment.The first-age fish fed with feed No.1 was selected as the test fish,which divided into four groups: F1,F2,F3 and F4,then No.1 bait was changed by No.2 bait to feed for 5 weeks.Make ues of anatomy,histology,histochemistry,transcriptomics,physiological and biochemical determination to explore its adaptation mechanism.The main results are as follows:1.The results of anatomical studies showed that the total length of Schizopygopsis youughusbaudi did not change significantly(P>0.05)in all groups,but for the weight of F4 group decreased significantly at 35 th d(P<0.05).In addition,the survival rate of all groups were all 100%.The gut of the fish adapting to bait-restricted by prolonging gut emptying and reducing the speed of the bait in the gut,moreover does not endanger it’s life.2.The results of histological studies showed that the fish’s gut structure changed adaptively and could adapt to the bait-restricted.When the bait-restricted(F3,F4),the foregut,midgut,and hindgut of the fish would increased the nutrient absorption area and digestive enzyme activity adjust gut activity to maintain the nutrient absorption capacity,and make full use of the nutrients from the bait.3.The results of physiological and biochemical measurements and histochemical studies showed that an upward and downward adaptive adjustment trend of the fish’s whole gut digestive enzyme activity with time,which showed that increasing digestive enzyme activity is a strategy for Schizopygopsis youughusbaudi to adapt to bait-restricted.The number of Glu-positive cells in the foregut,midgut and hindgut showed an adaptive adjustment trend with time too,which does not affected when bait-restricted.4.The results of transcriptomics research showed that the mapping rate was80.59%∽88.23% after comparison with the reference whole genome.The analysis by KEGG and GO found that up-regulating the catalytically active enzymes and solute carrier family genes of the digestive system,thereby improving the digestion and absorption of proteins,fats and carbohydrates,increasing the transportation of essential amino acids,mineral ions and vitamins,which were the fish’s response to bait-restricted.5.A scoring system was established to comprehensively evaluate the gut function and adaptability of Schizopygopsis youughusbaudi with bait-restricted(The formula was:Ai/(?)Ai*100*OS)in this paper.The results showed that the fish had the best gut function in the F3 group,with all total score exceeding 72.6216 points.Based on the high plasticity of the gut,the fish gut has strong plasticity and adaptability to the bait-restricted.In addition,it’s could considered that feeding once every 2 days is a better method to cultivar adult fish of Schizopygopsis youughusbaudi in the short term. |
