Acclimatory responses of thermal physiological performances in hatchling yellow pond turtles (Mauremys mutica)

Abstract

Temperature is a crucial environmental factor that can strongly impact animal physiology. Here, we acclimated hatchling of Asian yellow pond turtles (Mauremys mutica) to one of two different temperatures (25 or 30°C) for four weeks to determine temperature acclimation effects on their physiology. All four measured physiological variables (righting time, resting metabolic rate, critical thermal minimum and critical thermal maximum) were significantly affected by temperature acclimation. Turtles acclimated to 25°C righted themselves more slowly and had a lower mean metabolic rate than 30°C-acclimated turtles. Turtles acclimated to 25°C were more resistant to low temperatures, but less resistant to high temperatures than 30°C-acclimated turtles, as measured by critical thermal limits. The thermal resistance range (i.e., the difference between critical thermal minimum and maximum) did not differ between the two acclimation groups. Compared with other semi-aquatic turtles, M. mutica had relatively higher acclimation response ratios for its critical thermal minimum and critical thermal maximum. Our results indicate that acclimation to relatively moderate temperatures could also produce significant responses in the thermal physiology of turtles.

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

“…Thus, the ten turtles from the recovery group experienced 1 week heat wave exposure and 1 week recovery. Overall, the thermal regime of the control group covered the set-point temperature range of M. mutica (25-29 • C, unpublished data), and the thermal peak during the heat wave was approximately 2 • C below the critical thermal maximum of M. mutica (approximately 41 • C, according to Lu et al, 2020).…”

“…One possible explanation was exhaustion of the cellular stress responses indicated by the decreased hepatosomatic index as described above. Another possible reason may be that the heat wave climax or the duration of heat stress was insufficient to activate high expression of HSPs, and high-temperature resistance of hatchling M. mutica would be elevated after warm acclimation (Lu et al, 2020). Future work to explore whether 1-week heat waves would enhance turtle tolerance to high temperatures is warranted.…”

“…The Asian yellow pond turtle (Mauremys mutica) is an aquatic turtle distributed in China, Japan, and Vietnam. It has been classified as "endangered" on the IUCN red list but is commonly cultured in southern China due to its high economic value as food, pets, and in traditional Chinese medicine (Lu et al, 2020;Wei et al, 2020). Recent studies have shown that extreme heat stress could downregulate the expression of immunity-associated genes in M. mutica, which may be the main reason underlying the increased morbidity and mortality rates associated with extreme heat events in turtle farms (Wei et al, 2020;Gao et al, 2021).…”