Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland.
Gen Comp Endocrinol. 2012 Apr 1;176(2):211-4. doi: 10.1016/j.ygcen.2012.01.013. Epub 2012 Feb 2.
Exposure of mothers to risk of predation can induce phenotypic changes in offspring as shown in several species. We previously found that cross-fostered great tit (Parus major) chicks of females exposed to increased predation risk were smaller and lighter, but had faster wing growth than control cross-fostered chicks, possibly improving predator-escaping abilities. Here we examined the possible role of maternal steroids deposited in eggs as an underlying mechanism. We collected eggs from female great tits under either experimentally increased predation risk (PRED) or control treatments (CON) and analyzed the concentration of testosterone, androstenedione, and progesterone in the yolks. PRED eggs contained lower levels of testosterone than CON eggs, but levels of androstenedione and progesterone did not differ. The smaller size and mass of chicks found in the previous study may thus be explained by the lower testosterone concentrations, since yolk testosterone is known to boost growth and development. Alternatively, testosterone may act as a modulator of differential investment into morphological traits, rather than a simple growth enhancer, explaining lower body mass in conjunction with the accelerated wing growth. This could possibly occur concurrently with other hormones such as corticosterone.
母亲面临捕食风险会使后代出现表型变化，这在多个物种中都有体现。我们之前发现，处于捕食风险增加环境中的麻雀（Parus major）代孵雏鸟比对照组的代孵雏鸟体型更小、体重更轻，但翅膀生长速度更快，这可能提高了它们躲避捕食者的能力。在这里，我们研究了卵内母体类固醇作为潜在机制的可能作用。我们收集了处于增加捕食风险（PRED）或对照（CON）处理下的麻雀雌鸟的卵，并分析了卵黄中的睾酮、雄烯二酮和孕酮浓度。PRED 组的卵中睾酮浓度低于 CON 组，但雄烯二酮和孕酮的浓度没有差异。因此，前一项研究中发现的雏鸟体型较小和体重较轻可能可以用较低的睾酮浓度来解释，因为已知卵黄中的睾酮可以促进生长和发育。或者，睾酮可能作为形态特征差异投资的调节剂发挥作用，而不是简单的生长促进剂，这可以解释为什么体重较低，同时翅膀生长速度较快。这种情况可能与皮质酮等其他激素同时发生。
