Abstract
Investigating how highland amphibians respond to changes in ambient temperature may be of great significance for their fate prediction and effective conservation in the background of global warming. Here, using field individuals as the control group, we investigated the influence of high temperatures (20.5 and 25.5°C) and heat wave (15–26.6°C) on the thermal preference, critical thermal limits, locomotor performance, oxidative stress, and antioxidant enzyme activities in high-altitude frog Nanorana pleskei (3,490 m) endemic to the Qinghai-Tibet Plateau (QTP). After 2 weeks of acclimation to high temperatures and heat wave, the thermal preference (Tpref), critical thermal maximum (CTmax), and range of tolerable temperature significantly increased, while the critical thermal minimum (CTmin) was significantly decreased. The total time of jump to exhaustion significantly decreased, and burst swimming speed significantly increased in frogs acclimated in the high temperature and heat wave groups compared with the field group. In the high temperature group, the level of H2O2 and lipid peroxide (malondialdehyde, MDA), as well as the activities of glutathione peroxidase (GPX), glutathione reductase (GR), catalase (CAT), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC) significantly increased in the liver or muscle. However, in the heat wave group, the MDA content significantly decreased in the liver, and antioxidants activities decreased in the liver and muscle except for CAT activities that were significantly increased in the liver. These results indicated that N. pleskei could respond to the oxidative stress caused by high temperatures by enhancing the activity of antioxidant enzymes. The heat wave did not appear to cause oxidative damage in N. pleskei, which may be attributed to the fact that they have successfully adapted to the dramatic temperature fluctuations on the QTP.
Highlights
In the background of global warming, the annual average air temperature in Qinghai Tibet Plateau (QTP) is increasing, with increase in frequency and intensity of extreme temperature events (Stocker et al, 2014; Zhao et al, 2014; Yi et al, 2018)
Niu et al (2018) investigated oxidative stress and antioxidant defense in hibernating N. parkeri, and the results showed that the level of oxidative stress and oxidative damage was significantly increased, but that the total antioxidant capacity was significantly decreased compared with the summer frogs
The frogs were placed in a custom-made cuboid-shaped glass tank (120 cm × 15 cm × 30 cm) containing 10-cm deep water collected from the field, and a ruler with an accuracy of.1 cm was fixed at the bottom of the tank to record the distance of swimming
Summary
In the background of global warming, the annual average air temperature in Qinghai Tibet Plateau (QTP) is increasing, with increase in frequency and intensity of extreme temperature events (Stocker et al, 2014; Zhao et al, 2014; Yi et al, 2018). Poikilothermic vertebrates, such as amphibians and nonavian reptiles, have behavioral and weak physiological thermoregulatory mechanisms, their growth, reproduction, foraging, immunity, and competitiveness are affected by environmental temperatures (Panov and Mcqueen, 1998; Cherkasov et al, 2006; Pörtner and Farrell, 2008; Peng et al, 2020). Understanding how highland amphibians respond to climate warming and heat wave events may have great significance for their effective conservation
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