| In ectotherms,temperature affects all activities of the organism,and reversible thermal adaptation is considered to be an important mechanism for buffering the influence of temperature changes.This adaptability enables individuals to respond to environmental changes through behavioral and physiological adjustment.In recent years,the temperature on the Qinghai-Tibet Plateau has shown an obvious upward trend,and the frequency of extreme weather has also increased significantly.Nanorana pleskei is an endemic amphibian species on the Qinghai-Tibet Plateau.It is widely distributed on the plateau and can be used as a representative species to study the adaptability of amphibians to environmental changes on the plateau.In this study,the N.pleskei was used as the research sample,the acclimation temperatures were increased to 20.5?and 25.0?on the basis of the average day and night temperature(12.1±0.5?)in August in the field for the past five years(2015-2019),heat wave were also set,the field group was the control group,while the temperature increased to 20.5?(ETem20 group,Elevated temperature to 20.5?),temperature increased to 25.0?(ETem25 group,Elevated temperature to 25.0?)and the heat wave group(the diurnal temperature fluctuation range was 15.0-26.6?)were the experimental groups,to measure the thermal biology,locomotor performance,oxidative stress,antioxidant defense system and Hsp70 mRNA and Hsp90 mRNA expressions in liver and muscle under these temperature patterns,so as to explore the adaptation mechanism of N.pleskei to high temperature and heat wave in the background of plateau climate warming.The results of thermal biology and locomotor performance indicated that,compared with the field group,the thermal preference(Tpref),critical thermal maximum(CTmax)and range of tolerable temperature(?CT)were significantly increased in ETem20 group,ETem25 group and heat wave group,while critical thermal minimum(CTmin)was significantly decreased.Besides,compared with the wild group,there was no obvious difference in the total distance of jumping under different temperatures and heat wave,but the longest time decreased significantly and the swimming speed increased significantly.In this study,it was found that thermal preference of the frogs changed,the tolerable temperature range was wider,the burst performance increased,but the stamina decreased in different temperatures and heat wave when compared with the wild group.The results of the level of oxidative damage and the activities of key enzymes in the antioxidant protection system showed that,compared with the field group,the level of lipid peroxide(MDA)in the liver of the ETem20 and muscle of the ETem25 and the level of H2O2 in the liver of the ETem20 and liver and muscle of the ETem25 were significantly increased.In addition,compared with the field group,the activities of glutathione peroxidase(GPX),glutathione reductase(GR),catalase(CAT),superoxide dismutase(SOD)and total antioxidant capacity(T-AOC)in liver were significantly increased in ETem20,while those in muscle of the ETem20 were significantly decreased.The activities of GPX,SOD and T-AOC were notably enhanced,and the activities of GPX and GR were greatly enhanced in muscle of the ETem25 when compared with the field group.Besides,compared to field group,the activities of GPX,GR and SOD were expressively decreased in liver and muscle,while the activities of CAT were expressively increased in liver but expressively decreased in muscle of heat wave group.Furthermore,compared to field group,the expressions of Hsp70 mRNA and Hsp90 mRNA in the liver or muscle of N.pleskei were markedly increased in different temperatures and heat wave.These results indicated that,compared with the wild group,domestication of different temperature patterns caused different degrees of stress of N.pleskei,which was manifested in the change of oxidative damage,antioxidant enzyme activity and the increase of Hsp70 mRNA and Hsp90 mRNA expression in different tissues,especially under high temperature conditions.Most amphibians show plasticity in thermal biology and locomotor performance,which may be the main strategy for them to adapt to environmental temperature changes.It is of great significance to study the adaptability of thermal biology and locomotor performance of N.pleskei under high temperatures and heat wave for their fate prediction and effective protection.Our results suggested that the frogs can adapt to the warming of plateau climate and the increase of heat wave intensity by changing their preferred temperature,enhancing their thermal tolerance and locomotor performance.The results of biochemistry and molecular biology showed that N.pleskei could cope with the oxidative stress caused by the temperature rise and heat wave by enhancing the antioxidant enzyme activity and the expression of Hsp70 and Hsp90 mRNA.These results can provide a reference for the study of adaptation of other plateau amphibians and the protection of the Qinghai-Tibet Plateau ecosystem. |
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