Effects of Simulated Heat Wave on Oxidative Physiology and Immunity in Asian Yellow Pond Turtle (Mauremys mutica)

Global warming has led to an increase in the frequency, duration, and intensity of heat waves in the summer, which can cause frequent and acute heat stress on ectotherms. Thus, determining how ectothermic animals respond to heat waves has been attracting growing interest among ecologists. However, the physiological and biochemical responses to heat waves in reptiles, especially aquatic reptiles, are still poorly understood. The current study investigated the oxidant physiology, immunity, and expression levels of heat shock proteins (HSP) mRNA after exposure to a simulated heat wave (1 week, 35 ± 4°C), followed by a recovery period (1 week, 28 ± 4°C) in juvenile Asian yellow pond turtle (Mauremys mutica), a widely farmed aquatic turtle in East Asia. The contents of malondialdehyde (MDA) in the liver and muscle were not significantly affected by the heat wave or recovery. Of all antioxidant enzymes, only the activity of glutathione peroxidase (GSH-Px) in muscles increased after heat wave, while the total superoxide dismutase (T-SOD), catalase activity (CAT), and total antioxidant capacity (T-AOC) did not change during the study. The organo-somatic index for the liver and spleen of M. mutica decreased after the heat wave but increased to the initial level after recovery. In contrast, plasma lysozyme activity and serum complement C4 levels increased after the heat wave, returning to the control level after recovery. In addition, heat waves did not alter the relative expression of HSP60, HSP70, and HSP90 mRNA in the liver. Eventually, heat wave slightly increased the IBR/n index. Therefore, our results suggested that heat waves did not lead to oxidative damage to lipids in M. mutica, but deleteriously affected the turtles’ immune organs. Meanwhile, the constitutive levels of most antioxidative enzyme activities, HSPs and enhanced blood immune functions might protect the turtles from the threat of heat waves under the current climate scenarios.

Variation in reproductive output as a function of maternal age and weather conditions in the cultured Asian yellow pond turtle, Mauremys mutica

Biotic factors (e.g., maternal age) and abiotic factors (e.g., weather) play vital roles in reproduction. However, there is little information about the combined effects of maternal age and weather on the reproductive output of cultured Asian yellow pond turtles, Mauremys mutica. To address this issue, we surveyed and compared the reproductive output of 13-year-old and 25-year-old female turtles on non-rainy and rainy days. The results showed that older females produced larger eggs than younger females regardless of the weather conditions. Females laid larger clutch sizes (number of eggs per nest) under non-rainy conditions compared with those under rainy conditions. However, the variation in clutch frequency (number of clutches per day) was independent of maternal age and weather. There was no effect of an interaction between maternal age and weather on egg mass, clutch size or clutch frequency. Our results suggest that maternal age and weather had significant effects on egg mass and clutch size, respectively. These results imply that maternal age, together with weather conditions (mainly conditions of rain), can affect the reproductive output of M. mutica. Our results provide useful information for the artificial breeding and stock management of M. mutica.