Ruuskanen Suvi, Groothuis Ton G G, Schaper Sonja V, Darras Veerle M, de Vries Bonnie, Visser Marcel E
Section of Ecology, Department of Biology, University of Turku, Finland; Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), The Netherlands.
Groningen Institute for Evolutionary Life Sciences, University of Groningen, The Netherlands.
Gen Comp Endocrinol. 2016 Sep 1;235:29-37. doi: 10.1016/j.ygcen.2016.05.026. Epub 2016 May 30.
Global warming has substantially changed the environment, but the mechanisms to cope with these changes in animals, including the role of maternal effects, are poorly understood. Maternal effects via hormones deposited in eggs, have important environment-dependent effects on offspring development and fitness: thus females are expected to adjust these hormones to the environment, such as the ambient temperature. Longer-term temperature variation could function as a cue, predicting chick rearing conditions to which yolk hormone levels are adjusted, while short-term temperature variation during egg formation may causally affect hormone transfer to eggs. We studied the effects of ambient temperature on yolk androgens (testosterone and androstenedione) and thyroid hormones (thyroxine and triiodothyronine) in great tits (Parus major) using data from unmanipulated clutches from a wild population and from aviary birds (ad libitum food) exposed to different experimental temperature treatments during five years. Both in the wild and in captivity, longer-term pre-laying ambient temperature was not associated with clutch mean yolk hormone levels, while the way androstenedione and thyroxine levels varied across the laying sequence did associate with pre-laying temperature in the wild. Yolk testosterone levels were positively correlated with short-term temperature (during yolk formation) changes within clutches in both wild and captivity. We also report, for the first time in a wild bird, that yolk thyroxine levels correlated with a key environmental factor: thyroxine levels were negatively correlated with ambient temperature during egg formation. Thus, yolk hormone levels, especially testosterone, seem to be causally affected by ambient temperature. These short-term effects might reflect physiological changes in females with changes in ambient temperature. The adaptive value of the variation with ambient temperatures pre-laying or during egg formation should be studied with hormone manipulations in different thermal environments.
全球变暖已极大地改变了环境，但动物应对这些变化的机制，包括母体效应的作用，却鲜为人知。通过沉积在卵中的激素产生的母体效应，对后代的发育和适应性具有重要的环境依赖性影响：因此，预计雌性会根据环境，如环境温度来调整这些激素。长期的温度变化可能作为一种线索，预测雏鸟饲养条件，据此调整卵黄激素水平，而在卵形成过程中的短期温度变化可能会因果性地影响激素向卵中的转移。我们利用来自野生种群未受操控的窝卵数数据以及来自在五年中接受不同实验温度处理的笼养鸟类（自由采食）的数据，研究了环境温度对大山雀（Parus major）卵黄雄激素（睾酮和雄烯二酮）和甲状腺激素（甲状腺素和三碘甲状腺原氨酸）的影响。在野外和圈养环境中，产卵前的长期环境温度均与窝卵数平均卵黄激素水平无关，而在野外，雄烯二酮和甲状腺素水平在产卵序列中的变化方式与产卵前温度有关。在野外和圈养环境中，卵黄睾酮水平均与窝卵数内（卵黄形成期间）的短期温度变化呈正相关。我们还首次在野生鸟类中报告，卵黄甲状腺素水平与一个关键环境因素相关：甲状腺素水平与卵形成期间的环境温度呈负相关。因此，卵黄激素水平，尤其是睾酮，似乎会受到环境温度的因果性影响。这些短期影响可能反映了雌性随着环境温度变化而发生的生理变化。产卵前或卵形成期间随环境温度变化的适应性价值，应通过在不同热环境中进行激素操纵来研究。
