Anuran larvae show phenotypic plasticity in age and size at metamorphosis as a response to temperature variation. The capacity for temperature-induced developmental plasticity is determined by the thermal adaptation of a population. Multiple factors such as physiological responses to changing environmental conditions, however, might influence this capacity as well. In anuran larvae, thyroid hormone (TH) levels control growth and developmental rate and changes in TH status are a well-known stress response to sub-optimal environmental conditions. We investigated how chemically altered TH levels affect the capacity to exhibit temperature-induced developmental plasticity in larvae of the African clawed frog (Xenopus laevis) and the common frog (Rana temporaria). In both species, TH level influenced growth and developmental rate and modified the capacity for temperature-induced developmental plasticity. High TH levels reduced thermal sensitivity of metamorphic traits up to 57% (R. temporaria) and 36% (X. laevis). Rates of growth and development were more plastic in response to temperature in X. laevis (+30%) than in R. temporaria (+6%). Plasticity in rates of growth and development is beneficial to larvae in heterogeneous habitats as it allows a more rapid transition into the juvenile stage where rates of mortality are lower. Therefore, environmental stressors that increase endogenous TH levels and reduce temperature-dependent plasticity may increase risks and the vulnerability of anuran larvae. As TH status also influences metabolism, future studies should investigate whether reductions in physiological plasticity also increases the vulnerability of tadpoles to global change.

中文翻译：

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改变的甲状腺激素水平影响林蛙和非洲爪蟾幼虫温度诱导的发育可塑性能力

Anuran 幼虫在变态时显示出年龄和大小的表型可塑性，作为对温度变化的响应。温度诱导的发育可塑性能力取决于种群的热适应能力。然而，多种因素，例如对不断变化的环境条件的生理反应，也可能影响这种能力。在无尾蚴幼虫中，甲状腺激素 (TH) 水平控制着生长和发育速度，并且 TH 状态的变化是众所周知的对次优环境条件的应激反应。我们研究了化学改变的 TH 水平如何影响非洲爪蛙 (Xenopus laevis) 和普通蛙 (Rana temporaria) 幼虫表现出温度诱导的发育可塑性的能力。在这两个物种中，TH 水平影响生长和发育速率并改变温度诱导的发育可塑性能力。高 TH 水平将变质性状的热敏感性降低了 57% (R. temporaria) 和 36% (X. laevis)。X. laevis (+30%) 的生长和发育速率对温度的响应比 R. temporaria (+6%) 更具可塑性。生长和发育速度的可塑性有利于异质栖息地中的幼虫，因为它可以更快地过渡到死亡率较低的幼虫阶段。因此，增加内源性 TH 水平和降低温度依赖性可塑性的环境压力可能会增加无尾蚴幼虫的风险和脆弱性。由于 TH 状态也会影响新陈代谢，