A Comparative Study On The Thermal Acclimatization And Physio-biochemical Characteristics Of Strauchbufo Raddei Tadpoles From Different Altitudes

Strauchbufo raddei belongs to Amphibia,Anura,Bufonidae,Strauchbufo.It is a widely distributed species in northern China and one of the most commonly used animals for basic research in biology,medicine and ecology.Previous studies have focused on feeding habits,reproduction and responses to heavy metal pollution et al.However,under the background of global warming,there is no reports on the thermal adaptability and physio-biochemical characteristics of Strauchbufo raddei tadpoles.The ability of amphibians to respond to thermal acclimation determines their ability to adapt to the surrounding thermal environment and the fate with climate change in future.Therefore,we selected the tadpoles of Strauchbufo raddei in high altitude population(2292 m in Gui De,Qing Hai)and low altitude population(1488 m in Yong Jing,Gan Su)to study the responses to thermal acclimatization.These tadpoles of Strauchbufo raddei was acclimated to different temperature(14,18,22,26,30?)for two weeks.To explore and compare the effects of temperature on the early growth of tadpoles at high and low altitudes,we measured the main growth and development indexes of Strauchbufo raddei tadpoles from high and low altitudes,including total body length,body width,tail height,tail length,body weight,and developmental stage.The thermal tolerance of Strauchbufo raddei tadpoles,including the critical thermal maximum(CTmax),critical thermal minimum(CTmin),preferred temperature,avoidance temperature,lethal thermal maxima(LTM)and acclimation response ratio(ARR)were measured to realize and compare the physiological response and thermal tolerance characteristics of tadpoles at high and low altitudes and to evaluate their vulnerability to global climate change in the future.In addition,we also measured the standard metabolic rate(SMR),maximum burst swimming speed and the activities of key metabolic enzymes including citrate synthase(CS),lactate dehydrogenase(LDH),cytochrome c oxidase(CCO)and ATPase in the main metabolic pathways of Strauchbufo raddei tadpoles from high and low altitudes so that we can explore the thermal adaptation strategy of metabolism and locomotion of tadpoles.The results of growth and development experiments showed that acclimation temperature had significant effects on the total body length,body width,tail length,body weight of Strauchbufo raddei tadpoles at high and low altitudes.With the increase of acclimation temperature,the growth and developmental stage of tadpoles were accelerated.22?is suitable for Strauchbufo raddei tadpoles to growth in the low altitude group,while 26?is more suitable for Strauchbufo raddei tadpoles to growth in the high altitude group.In general,there are some differences in the response of tadpole growth and development to temperature between high and low altitude population.The tadpoles of Strauchbufo raddei from high altitude were larger,accumulated more energy and metamorphosed faster than those in low altitude area.The results of thermal tolerance experiment showed that the thermal tolerance of Strauchbufo raddei tadpoles was significantly affected by acclimation temperature.The results as follows:(1)The CTmax of Strauchbufo raddei tadpoles in high and low altitude groups increased with the increase of acclimation temperature,while the CTmin decreased with the decrease of acclimation temperature.(2)The maximum thermal tolerance amplitude of tadpoles in the low altitude group was 29.93?,while the maximum thermal tolerance amplitude of tadpoles in the high altitude group was31.52?.(3)At 14-30?,the thermal tolerance area of tadpoles in the low altitude group was 470.5?²,and that in the high altitude group was 491.6?².(4)The avoidance temperature,lethal thermal maxima,preferred temperature and the range of preferred temperature of tadpoles increased with the increase of acclimation temperature.(5)The acclimation response ratio of CTmax,CTmin,avoidance temperature and lethal thermal maxima of Strauchbufo raddei tadpoles in high altitude group was higher than that in low altitude group.That is to say,the effect of acclimation temperature on the high altitude group was greater than that in low altitude group.The results showed that the tadpoles of Strauchbufo raddei in high altitude had higher thermal tolerance and plasticity than those tadpoles from low altitude.We speculated that the tadpoles in low altitude areas were more vulnerable to global warming than those in high altitude areas.The experimental results of locomotion and metabolic showed that:(1)The burst swimming speed of tadpoles in different acclimation temperature groups at high and low altitudes increased firstly and then decreased with the increase of test temperature,and the maximum burst swimming speed of tadpoles in the high altitude group was larger than that in the low altitude group.(2)The maximum burst swimming speed(V_max')of tadpoles in the high altitude group was higher than that in the low altitude group.And the thermal performance width(B80)and optimal temperature range(B95)of tadpoles were better than those of the low altitude group.(3)The standard metabolic rate of tadpoles acclimated to low temperature was significantly higher than that of tadpoles acclimated to high temperature.And the standard metabolic rate of tadpoles in the low altitude group was higher than that in the high-altitude group at other temperature acclimation conditions except 22?acclimation condition.(4)The activity of CS and CCO increased with the decrease of acclimation temperature,and the low temperature acclimation resulted in CS and CCO compensation.Compared with CS,CCO had a lower degree of adaptation.The activity of LDH increased with the increase of acclimation temperature,without obvious compensation.The tail ATPase activity increased firstly and then decreased with the increase of acclimation temperature.Based on the findings mentioned above we suggest that the tadpoles of Strauchbufo raddei at high and low altitudes possess the features for them to adapt to their own environment and the tadpoles at high altitude have stronger thermal adaptability.