Temperature and Diet Acclimation Modify the Acute Thermal Performance of the Largest Extant Amphibian

Abstract

The Chinese giant salamander (Andrias davidianus), one of the largest extant amphibian species, has dramatically declined in the wild. As an ectotherm, it may be further threatened by climate change. Therefore, understanding the thermal physiology of this species should be the priority to formulate related conservation strategies. In this study, the plasticity in metabolic rate and thermal tolerance limits of A. davidianus larvae were studied. Specifically, the larvae were acclimated to three temperature levels (7 °C, cold stress; 15 °C, optimum; and 25 °C, heat stress) and two diet items (red worm or fish fray) for 20 days. Our results indicated that cold-acclimated larvae showed increased metabolic capacity, while warm-acclimated larvae showed a decrease in metabolic capacity. These results suggested the existence of thermal compensation. Moreover, the thermal tolerance windows of cold-acclimated and warm-acclimated larvae shifted to cooler and hotter ranges, respectively. Metabolic capacity is not affected by diet but fish-fed larvae showed superiority in both cold and heat tolerance, potentially due to the input of greater nutrient loads. Overall, our results suggested a plastic thermal tolerance of A. davidianus in response to temperature and diet variations. These results are meaningful in guiding the conservation of this species.

Rising floor and dropping ceiling: organ heterogeneity in response to cold acclimation of the largest extant amphibian

“…We previously demonstrated cold acclimation in A. davidianus larvae, which was characterized by improved metabolic rate and locomotive performance under cold conditions [18]. In this study, we observed a comprehensive transcriptional upregulation of substrate metabolism (e.g.…”

“…The brain, liver, tail and limb accounts for a large proportion of the individual metabolic rate and are responsible for the maintenance of locomotive activities. Their cold-induced changes can explain the increased metabolic rate and lower critical temperature in the cold-acclimated A. davidianus larvae [18]. Interestingly, we observed increased cold preference in the cold-acclimated larvae (figure 1a).…”

“…Given that cardiac function is fundamental to the delivery of oxygen and nutrient to other tissues, its thermal property likely constitutes a systemic ‘ceiling’ for metabolic capacity and compensation intensity at the whole-organism level. Although this ‘ceiling’ did not constrain the basal metabolism at 7°C [18], it may become a compelling limiting factor for metabolism at cooler temperatures. Reduced heart rate is a major feature of mammal hibernation, and adaptive changes in gene expression in the heart before hibernation may be indispensable for acquiring cold resistance [52].…”

“…Their optimal growth temperature in water ranges from is 15 to 21°C [39]. Our previous studies suggested that A. davidianus larvae acclimated to 7°C showed superior cold tolerance and upregulated their metabolic capacity in comparison to their 15°C counterparts [18]. This is suggestive of cold acclimation in this species.…”

“…reducing the lower thermal limits for locomotive activity) and optimize physiological performance (e.g. encouraging respiration rate) under thermal stress [17][18][19]. It allows animals to maintain their physiological activities (e.g.…”