![]() Because of the non-linear response of metabolic rate to temperature change, fluctuating temperatures can increase the energy demand required for cell maintenance at higher temperatures. Thermal variability can impact upon the fitness of ectotherms through effects on growth, reproduction and whole-animal performance as a consequence of the thermal sensitivity of underlying physiological processes ( Huey and Stevenson, 1979 Huey, 1982). ornatum tadpoles to maintain performance in the thermal variability inherent in their environment. Thermal independence of key traits may allow P. Temperature treatment and UV-B exposure had an interactive effect on upper critical thermal limits possibly due to the upregulation of the cellular stress response. Maintenance of performance led to a trade-off for growth under fluctuating temperatures and UV-B exposure. ornatum tadpoles were thermally insensitive for both burst swimming performance, across the range of temperatures tested, and resting metabolic rate at high temperatures independent of developmental conditions. We hypothesised that developmental responses to thermal fluctuations would increase thermal tolerance and reduce thermal dependence of physiological traits, and that trade-offs in the allocation of metabolic resources towards repairing UV-B-induced damage may limit the ability to maintain performance over the full range of temperatures experienced. Tadpoles were tested for upper critical thermal limits, thermal dependence of resting metabolic rate and maximum burst swimming performance. Tadpoles developed in either stable (24☌) or fluctuating temperatures (18–32☌) under high or low UV-B conditions. Here, we investigated how development in fluctuating versus stable temperature conditions in the presence of high or low UV-B radiation influences thermal tolerance and thermal sensitivity of performance traits of P. ![]() Ornate burrowing frog ( Platyplectrum ornatum) tadpoles develop in shallow ephemeral pools that experience high diel thermal variability (>20☌) and can be exposed to high levels of UV-B radiation. Additional stressors may limit the ability of animals to respond to these thermally challenging environments through changes to energy partitioning or interactive effects. When ectotherms face the challenge of large diel temperature fluctuations, one strategy may be to reduce the thermal sensitivity of key traits in order to maintain performance across the range of temperatures experienced. Animals may overcome the challenges of temperature instability through behavioural and physiological mechanisms in response to short- and long-term temperature changes.
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