DataSheet1_A prenatal acoustic signal of heat reduces a biomarker of chronic stress at adulthood across seasons.csv

During development, phenotype can be adaptively modulated by environmental conditions, sometimes in the long-term. However, with weather variability increasing under climate change, the potential for maladaptive long-term responses to environmental variations may increase. In the arid-adapted zebra finch, parents emit “heat-calls” when experiencing heat during incubation, which adaptively affects offspring growth in the heat, and adult heat tolerance. This suggests that heat-call exposure may adjust individual phenotype to hot conditions, potentially compromising individual sensitivity to cool weather conditions. To test this hypothesis, we manipulated individual prenatal acoustic and postnatal thermal experiences during development, and sought to assess subsequent chronic responses to thermal fluctuations at adulthood. We thus measured heterophil to lymphocyte (H/L) ratios in adults, when held in outdoor aviaries during two summers and two winters. We found that birds exposed to heat-calls as embryos, had consistently lower H/L ratios than controls at adulthood, indicative of lower chronic stress, irrespective of the season. Nonetheless, in all birds, the H/L ratio did vary with short-term weather fluctuations (2, 5 or 7 days), increasing at more extreme (low and high) air temperatures. In addition, the H/L ratio was higher in males than females. Overall, while H/L ratio may reflect how individuals were being impacted by temperature, heat-call exposed individuals did not show a stronger chronic response in winter, and instead appeared more resilient to thermal variability than control individuals. Our findings therefore suggest that heat-call exposure did not compromise individual sensitivity to low temperatures at adulthood. Our study also reveals that prenatal sound can lead to long-term differences in individual physiology or quality/condition, as reflected by H/L ratios, which are consistent with previously-demonstrated reproductive fitness differences.

在数据集的开发过程中，表型可能会受到环境条件的适应性调节，有时这种调节作用是长期的。然而，随着气候变化下气象变率的增加，对环境变化产生不良长期响应的可能性也在提高。在适应干旱环境的斑马雀中，父母在孵化期间遭遇高温时会发出‘热呼叫’，这种适应性调节会影响后代在高温下的生长和成年后的耐热性。这表明，热呼叫的暴露可能调节个体表型以适应炎热条件，从而可能损害个体对凉爽天气条件的敏感性。为了验证这一假设，我们在发育过程中操纵了个体胚胎期的声学体验和出生后的热体验，并试图评估成年后对温度波动的慢性反应。因此，我们在两个夏季和两个冬季将成年鸟保持在户外鸟舍中，测量了异嗜细胞与淋巴细胞（H/L）比率。我们发现，作为胚胎接触热呼叫的鸟类，其成年后的H/L比率显著低于对照组，这表明无论季节如何，慢性压力均较低。尽管如此，在所有鸟类中，H/L比率均随短期（2、5或7天）天气波动而变化，在极端（低温和高温）空气温度下增加。此外，雄性的H/L比率高于雌性。总体而言，尽管H/L比率可能反映了个体受到温度的影响程度，但接触热呼叫的个体在冬季并未显示出更强的慢性反应，反而似乎比对照组更能抵抗温度变化。因此，我们的研究结果提示，热呼叫的暴露并未损害成年个体对低温的敏感性。本研究还揭示，胚胎期的声音可以导致个体生理或质量/状况的长期差异，这由H/L比率体现，并与先前证明的繁殖力差异相一致。