Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Eberhard-Gwinner-Straße, Haus 7/8, D-82319 Seewiesen, Germany.
Gen Comp Endocrinol. 2011 Feb 1;170(3):501-8. doi: 10.1016/j.ygcen.2010.11.007. Epub 2010 Nov 13.
The steroid hormone testosterone (T) plays a central role in the regulation of reproduction in animals. Although seasonal variation in T levels is well-studied, differences between day and night have only been described in relatively few species, and daily within-individual variation has been largely neglected when evaluating the relationship between T and the expression of sexual ornaments or behavior. We measured plasma T levels during day and night in a captive population of House Sparrows, and analyzed their relationship with an important male ornament--badge size. T levels were on average twice as high at night than during daytime. This was true in all seasons, and in both males and females. Disturbance of the birds at night, but not during the day, led to significantly lower T levels, suggesting a rapid drop after an individual wakes up. The relationship between T levels and badge size depended on the time when T was measured. During the breeding season, badge size was strongly positively correlated with night-time, but not with daytime T levels. This suggests that badge size signals information related to an individual's maximum potential T level such as social dominance. Our study highlights that integrative research on the endocrine control of ornament expression needs to take diel variation in hormone levels into account.
类固醇激素睾酮（T）在动物生殖调控中起着核心作用。尽管 T 水平的季节性变化已经得到了充分研究，但昼夜差异仅在少数几个物种中得到描述，并且在评估 T 与性装饰物或行为表达之间的关系时，个体内部的日常变化很大程度上被忽视了。我们在一个圈养的麻雀种群中测量了白天和夜间的血浆 T 水平，并分析了它们与一个重要的雄性装饰物——徽章大小的关系。T 水平在夜间平均比白天高两倍。这在所有季节都是如此，而且在雄性和雌性中都是如此。夜间而不是白天干扰鸟类会导致 T 水平显著降低，这表明个体醒来后 T 水平会迅速下降。T 水平与徽章大小之间的关系取决于测量 T 的时间。在繁殖季节，徽章大小与夜间 T 水平呈强烈正相关，但与白天 T 水平无关。这表明徽章大小可以反映与个体最大潜在 T 水平相关的信息，如社会优势。我们的研究强调，对装饰物表达的内分泌控制进行综合研究需要考虑激素水平的昼夜变化。
