Blas Julio, Baos Raquel, Bortolotti Gary R, Marchant Tracy A, Hiraldo Fernando
Department of Biology, University of Saskatchewan, Sask., Canada S7N 5E2.
Gen Comp Endocrinol. 2006 Sep 1;148(2):172-80. doi: 10.1016/j.ygcen.2006.02.011. Epub 2006 Apr 19.
The post-natal development of the adrenocortical response to stress was investigated in European white storks. Sixty wild nestlings aged 24-59 days old were subjected to a standardized capture and restraint protocol, and the time-course pattern of the response to stress was assessed through determination of circulating corticosterone in blood samples collected at five fixed times during the 45-min period following capture. The time course of the response was best fit to a third-order function of handling time, and showed a strong effect of age. Although age did not affect baseline titers and all birds showed a positive post-capture increase in circulating corticosterone, age had a positive effect on the relative increase from baseline titer, the recorded time to reach maximum level, and the acute concentration after 10 min following capture and restraint. While young nestlings displayed very little response to capture, the response near fledging resembled the typical adrenocortical pattern widely reported in fully developed birds. Our results concur with those found in altricial and semi-altricial species, and suggest that non-precocial birds follow a similar mode of development of the hypothalamic-pituitary-adrenal (HPA) axis. The fact that HPA sensitivity to stress is functional suggests that young storks gradually develop emergency responses of adaptive value and are able to overcome acute perturbations in spite of their parental dependence, at least during the last two-thirds of post-natal development. According to the Developmental Hypothesis, such gradual changes would allow nestlings to respond to perturbations as a function of the specific behavioral and physiological abilities of their age. The potential sources of stress that nestlings have to face during development (i.e., weather conditions, dietary restrictions, and social competition) are discussed according to developmental changes in behavioral and physiological abilities.
对欧洲白鹳肾上腺皮质对应激反应的产后发育进行了研究。60只年龄在24至59天的野生雏鸟接受了标准化的捕捉和约束方案，并通过测定在捕捉后45分钟内五个固定时间采集的血样中循环皮质酮来评估对应激反应的时间进程模式。反应的时间进程最适合处理时间的三阶函数，并显示出年龄的强烈影响。尽管年龄不影响基线水平，且所有鸟类在捕捉后循环皮质酮均有阳性增加，但年龄对相对于基线水平的相对增加、达到最大水平的记录时间以及捕捉和约束后10分钟的急性浓度有积极影响。幼雏对捕捉的反应很小，而接近 fledging 时的反应类似于在完全发育的鸟类中广泛报道的典型肾上腺皮质模式。我们的结果与在晚成雏和半晚成雏物种中发现的结果一致，并表明非早成雏鸟类遵循类似的下丘脑 - 垂体 - 肾上腺（HPA）轴发育模式。HPA对应激的敏感性具有功能这一事实表明，幼鹳逐渐发展出具有适应性价值的应急反应，并且尽管它们依赖父母，但至少在产后发育的最后三分之二时间里能够克服急性干扰。根据发育假说，这种逐渐变化将使雏鸟能够根据其年龄的特定行为和生理能力对干扰做出反应。根据行为和生理能力的发育变化，讨论了雏鸟在发育过程中必须面对的潜在应激源（即天气条件、饮食限制和社会竞争）。
