Organisms exhibit reversible physiological adjustments as a response to rapidly changing environments. Yet such plasticity of the phenotype is gradual and may lag behind environmental fluctuations, thereby affecting long-term average performance of the organisms. By supplying energy and essential compounds for optimal tissue building, food determines the range of possible phenotypic changes and potentially the rate at which they occur. Here, we assess how differences in the dietary supply of essential lipids modulate the phenotypic plasticity of an ectotherm facing thermal fluctuations. We use three phytoplankton strains to create a gradient of polyunsaturated fatty acid and sterol supply for Daphnia magna under constant and fluctuating temperatures. We used three different fluctuation periodicities to unravel the temporal dynamics of gradual plasticity and its long-term consequences for D. magna performance measured as juvenile somatic growth rate. In agreement with gradual plasticity theory, we show that in D. magna, fluctuation periodicity determines the differential between observed growth rates and those expected from constant conditions. Most importantly, we show that diet modulates both the size and the direction of the growth rate differential. Overall, we demonstrate that the nutritional context is essential for predicting ectotherm consumers' performance in fluctuating thermal environments.

中文翻译：

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食品质量塑造面临温度变化的变温动物的逐渐表型可塑性

作为对快速变化的环境的反应，生物体表现出可逆的生理调整。然而，表型的这种可塑性是渐进的，可能滞后于环境波动，从而影响生物体的长期平均性能。通过为最佳组织构建提供能量和必需化合物，食物决定了可能的表型变化的范围以及它们发生的速度。在这里，我们评估必需脂质膳食供应的差异如何调节面临热波动的变温动物的表型可塑性。我们使用三种浮游植物菌株在恒定和波动的温度下为大型溞创建多不饱和脂肪酸和甾醇供应的梯度。我们使用三种不同的波动周期来揭示逐渐可塑性的时间动态及其对D. magna性能（以幼年体细胞生长率衡量）的长期影响。与渐进可塑性理论一致，我们表明，在D. magna中，波动周期性决定了观察到的增长率与恒定条件下预期增长率之间的差异。最重要的是，我们表明饮食可以调节生长速率差异的大小和方向。总的来说，我们证明营养背景对于预测变温动物消费者在波动的热环境中的表现至关重要。