Adaptation Of The Digestive Tract Of Phrynocephalus Vlangalii To High Altitude

The Qinghai-Tibetan Plateau is characterized by hypothermia and hypoxia because of its unique geographical environment.Animals dwelling on high altitude have a long series of adaptations,especially ectotherms,which is a hot topic of current researches on reptile biology and evolution.However,the morphology and possible adaptive characteristics and transcriptome of digestive tract have not been found so far.In this thesis,the toad-headed agama living at Qinghai-Tibet Plateau(Phrynocephalus vlangalii)(Reptilia: Agamidae),which can occupy from altitude 2700 m to 4500 m and is believed as a good candidate on the topic,is sampled and studies.Digestive tract plays an important role in the process of energy budget.Therefore,Objective to investigate the adaptation of the digestive tract to energy limitation at high altitude in variable temperature animals,this study selected two populations of P.vlangalii at high and low altitudes,and studied the tissue structure and argyrophilic cells of their digestive tract using anatomical and paraffin section techniques to find the sites with obvious differences.And proteomic analysis was performed on the parts with significant differences to identify proteins that play a key role in the metabolism of nutrients and to investigate their adaptation systems to high altitude energy limitation.The research contents of this paper are as follows:1?The total digestive tract length of Maduo population was significantly larger than that of Delingha population,but there was no altitude difference between sexes in the digestive tract,and there was no interaction between sexes and populations.2?The length of the gastrointestinal part of the digestive tract of P.vlangalii differed significantly between high and low elevation populations: the length of both the stomach and ileum of the Maduo population was significantly greater than that of the Delingha population.There was no sex difference in the length of each part of the digestive tract,and there was no significant sex-population interaction.3?The number of duodenal villi in Maduo population of P.vlangalii was significantly greater than that in Delingha population;the length,width,and surface area of small intestinal villi in the duodenum and jejunum of the Maduo population were significantly greater than those of the Delingha population;the length of ileum in Maduo population was remarkably greater than that in Delingha population.The results indicated that the digestion and absorption ability of the high-altitude population of P.vlangalii was greatly enhanced.There were no sex differences in the number,length,width and surface area of villi in jejunum and ileum.4?The number of argyrophilic cells in the gastric body and duodenum of the Maduo population of P.vlangalii was significantly greater than that of the Delingha population,and the results indicated that the digestive capacity of P.vlangalii at high altitude was enhanced.There was no sex difference in the number of argyrophilic cells in various parts of the digestive tract,and there was no significant sex-population interaction.5?Gene Ontology study of distinguishingly expressed proteins revealed that many distinguishingly expressed proteins appeared in the digestive tract of the high altitude population of P.vlangalii,where the up-regulated proteins were involved in redox processes,glutathione metabolic processes,oxidoreductase activity,cofactor binding and catalytic activity;the functions of remarkably reduce-expressed proteins were mainly immune responses and processes,membrane attack complexes and other immune-related processes.6?Kyoto Encyclopedia of Genes and Genomes Pathway study of distinguishingly expressed proteins implied that distinguishingly expressed proteins were mainly gathered in metabolic pathways,natural killer cell-mediated cytotoxicity,amino acid metabolism,retinol metabolism,and other metabolic pathways.In summary,the digestive tract of P.vlangalii underwent significant changes in order to accommodate to the energy restriction caused by hypothermia and hypoxia at high altitude.The length of the digestive tract,the morphological structure of the small intestinal villi and the number of argyrophilic cells in the high-altitude population of P.vlangalii were significantly increased;the metabolic function of their intestines was significantly enhanced,especially the absorption,transport and metabolism of fat,which allowed them to obtain more energy.In addition,the immune capacity of the intestinal tract of the high-altitude population of P.vlangalii was reduced,decreasing the energy input to immunity.This adaptive change in the digestive tract of P.vlangalii adjusts the energy expenditure and income trade-offs,addressing to some extent the selective pressure of energy limitation at high altitude.