Data from: Stress hormones mediate predator-induced phenotypic plasticity in amphibian tadpoles

Amphibian tadpoles display extensive anti-predator phenotypic plasticity, reducing locomotory activity and, with chronic predator exposure, developing relatively smaller trunks and larger tails. In many vertebrates, predator exposure alters activity of the neuroendocrine stress axis. We investigated predator-induced effects on stress hormone production and the mechanistic link to anti-predator defences in Rana sylvatica tadpoles. Whole-body corticosterone (CORT) content was positively correlated with predator biomass in natural ponds. Exposure to caged predators in mesocosms caused a reduction in CORT by 4 hours, but increased CORT after 4 days. Tadpoles chronically exposed to exogenous CORT developed larger tails relative to their trunks, matching morphological changes induced by predator chemical cue; this predator effect was blocked by the corticosteroid biosynthesis inhibitor metyrapone. Tadpole tail explants treated in vitro with CORT increased tissue weight, suggesting that CORT acts directly on the tail. Short-term treatment of tadpoles with CORT increased predation mortality, likely due to increased locomotory activity. However, long-term CORT treatment enhanced survivorship, likely due to induced morphology. Our findings support the hypothesis that tadpole physiological and behavioural/morphological responses to predation are causally interrelated. Tadpoles initially suppress CORT and behaviour to avoid capture, but increase CORT with longer exposure, inducing adaptive phenotypic changes.两栖动物蝌蚪展现出显著的抗捕食者表型可塑性（anti-predator phenotypic plasticity），可降低自身运动活性；当长期暴露于捕食者环境时，其躯干相对更小、尾部相对更大。在多数脊椎动物类群中，捕食者暴露会改变神经内分泌应激轴（neuroendocrine stress axis）的活动水平。本研究以林蛙（Rana sylvatica）蝌蚪为研究对象，探究了捕食者诱导的应激激素生成变化，及其与抗捕食者防御机制之间的机制关联。 在自然池塘环境中，蝌蚪的全身皮质酮（corticosterone, CORT）含量与捕食者生物量呈正相关。在中宇宙（mesocosms）实验体系中，暴露于笼养捕食者的蝌蚪，其CORT水平在4小时内出现下降，但在4天后显著升高。 长期暴露于外源性皮质酮的蝌蚪，其尾部相对于躯干的比例显著增大，这与捕食者化学信号诱导的形态变化相一致；而皮质酮生物合成抑制剂美替拉酮（metyrapone）可阻断这一由捕食者诱导的形态效应。体外使用CORT处理的蝌蚪尾外植体组织重量增加，表明CORT可直接作用于尾部组织。 短期用CORT处理的蝌蚪捕食致死率升高，这大概率源于其运动活性增强；但长期CORT处理则提升了蝌蚪的存活率，这可能是其诱导的形态变化带来的适应性益处。本研究结果支持如下假说：蝌蚪针对捕食者的生理、行为与形态响应存在因果关联。蝌蚪最初会抑制CORT水平与行为以避免被捕食，但随着暴露时间延长会升高CORT水平，进而诱导适应性表型变化。