Effects Of High Temperature Stress On Physiology And Biochemistry Of Asian Yellow Pond Turtle(Mauremys Mutica)

The thermal environment has significant differences in different latitudes and seasons.Ectotherms distributed along the environmental gradients such as latitude gradient have formed significant thermal adaptability characteristics.The current rate of warming poses an unprecedented challenge to living things worldwide.Warm winters,heatwaves and other abnormal weather occur frequently,and global warming is increasingly severe.How the unpredictable warming climate affects the ectotherms represented by reptiles has become a research hotspot in the field of ecology.In this paper,the hatchlings of Asian yellow pond turtle(Mauremys mutica)are taken as the research object with the preferred body temperature(Tp),thermal tolerance(CTMax,CTMin)of different populations were compared and the effects of different seasons high temperature stress on oxidative stress and so on to explore how reptiles adapt to the changes in thermal environment.It provides a theoretical basis for the influence of climate warming on physiology and biochemistry of ectotherms.1.The comparison of preferred body temperature and thermal tolerance of different populations of Asian yellow pond turtle(Mauremys mutica)Preferred body temperature and thermal tolerance are important thermobiological parameters of ectotherms,which reflect the optimal adaptive and the range of possible survival temperature of ectotherms to thermal environment,are the basis of studying the influence of thermal environment on organisms.The thermophysical characteristics of ectotherms distributed along the latitude gradient may have significant geographical variation because of high plasticity.This study we use self-made temperature gradient slot(18?-40?)to measure preferred body temperature(Tp)and according to jerk determine critical hightemperature tolerance(CTMax)and critical low temperature tolerance(CTMin).The results show that Tp of the southern populations in the range of 25.04 ? to 30.39 ?,the mean of CTMax and CTMin are41.54 ? and 2.78 ?;Tp of the northern populations in the range of24.97 ? to 29.14 ?,the mean of CTMax and CTMin are 41.29 ? and1.96 ? respectively.There were no significant differences in Tp and CTMax but significant differences in CTMin between populations.It provides a theoretical basis for the study of thermobiological of Mauremys mutica.2.Oxidative responses to acute heat stress during hibernation of Asian yellow pond turtle(Mauremys mutica)Climate change is causing frequent and intensely warm winters.As a result,ectothermic animals are expected to face more frequent periods of heat stress during winter dormancy.However,how heat exposure affects oxidative stress and antioxidative defense in hibernating reptiles remains largely unknown.In this study,we explored the effect of acute heat stress(25?)on lipid peroxidation product malondialdehyde(MDA)and the antioxidant enzymes superoxide dismutase(SOD),catalase(CAT),and glutathione peroxidase(GSH-Px)in hatchlings of Asian yellow pond turtle(Mauremys mutica)from high and low latitudinal populations during hibernation at 6?.MDA content was higher in the livers of turtles from the southern population(P < 0.05),and increased further after turtles were returned to hibernation conditions(P < 0.05).MDA content in muscles of turtles from the northern population increased after heat stress(P < 0.05),but decreased to a level similar to that of the control group after moving back to 6? for 24 h(P > 0.05).SOD activity was not influenced by heat stress(P > 0.05).In livers of turtles from the southern population,CAT activity reached its highest level after heat stress for 2 h,and was significantly greater than that of turtles from the northern population at each sampling time(P < 0.05).GSH-Px activity in livers was greatest after heat exposure for 12 h in turtles from the northern population(P < 0.05).In conclusion,heat stress caused oxidative damage to Mauremys mutica during hibernation.The southern population may be more vulnerable to temperature fluctuations during hibernation,but it alsohas stronger antioxidant enzyme activity in response to the threat of heat stress.3.Effects of heat wave on oxidative stress,immunity and expression of heat shock protein(hsp70,hsp90)of Asian yellow pond turtle(Mauremys mutica)Heat waves are increasing more frequent and intense under the global warming.The ectotherms that are more vulnerable to climate change will face more frequent heat stress.However,studies on the effects of heat waves on the physiological and biochemical functions of ectotherms are still scarce.In this study,Asian yellow pond turtle(Mauremys mutica)was taken as the research object to explore the effects of heat wave on oxidative stress and immunity and the expression of hsp70 and hsp90.The results showed that the content of MDA and the activity of GSH-Px in liver were increased under the heat stress,but the activity of SOD,CAT and total antioxidant capacity(T-AOC)are increased not significantly.At the same time,the immune organ index of Mauremys mutica decreased after heat wave treatment,but there is no significant change in corticosterone level,while C4 content and lysozyme activity increased.In addition,heat wave has no significant effect on the expression of hsp70 and hsp90 genes.This study shows that heat wave can cause oxidative damage and depress immunity to of Mauremys mutica,but partial antioxidant enzymes and immune defense function are enhanced in order to cushion organism against the threat of heat wave.