Influence of High Temperatures and Heat Wave on Thermal Biology, Locomotor Performance, and Antioxidant System of High-Altitude Frog Nanorana pleskei Endemic to Qinghai-Tibet Plateau

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.

Impact of rising temperature on physiological and biochemical alterations that affect the viability of blood cells in American bullfrog crossbreeds

“…This phenomenon indicated that at 27 °C, frog body cells produced higher levels of hydrogen peroxide than at other environmental temperatures. The results of this study are consistent with the findings of He et al [ 26 ], who reported that exposure to high temperature environments and heat waves increased hydrogen peroxide levels in both the liver and muscle of Nanorana pleskei frogs.…”

“…The antioxidant system generally consists of enzymatic antioxidants, such as catalase, glutathione peroxidase, glutathione reductase, and superoxide dismutase, as well as non-enzymatic antioxidants, such as glutathione etc. [ 26 ]. The measure of total antioxidant power can be determined using all the antioxidants which were present in samples [ 63 ].…”

“…Generally, levels of reactive oxygen species remain stable, but if there is a transient increase, and they are not promptly removed, heightened reactive oxygen species can lead to oxidative stress [ 24 , 25 ]. When frogs are exposed to high environmental temperature, they experience oxidative stress and their total antioxidant capacity decreases [ 26 ]. Numerous studies have found that oxidative stress promotes cell death [ 27 ].…”

Potential Effects of High Temperature and Heat Wave on Nanorana pleskei Based on Transcriptomic Analysis

“…Cold acclimation reduces antioxidant defense in N. pleskei [ 32 ]. However, N. pleskei may have well adapted to the significant temperature fluctuation, according to a study on the impact of high temperatures and heat waves on thermal biology, locomotor performance, and antioxidant system [ 33 ]. The range of tolerated temperature, thermal preference, and critical thermal maximum all dramatically increased after two weeks of heat wave acclimation, whereas the critical thermal minimum significantly dropped [ 33 ].…”