D'Alba Liliana, Van Hemert Caroline, Spencer Karen A, Heidinger Britt J, Gill Lisa, Evans Neil P, Monaghan Pat, Handel Colleen M, Shawkey Matthew D
*Department of Biology, University of Akron, Akron, OH, USA; USGS Alaska Science Center, Anchorage, AK, USA; School of Psychology and Neuroscience, University of St. Andrews, Scotland, UK; Department of Biological Sciences, North Dakota State University, Fargo, ND, USA; Max Planck Institute for Ornithology, Seewiesen, Germany; Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
*Department of Biology, University of Akron, Akron, OH, USA; USGS Alaska Science Center, Anchorage, AK, USA; School of Psychology and Neuroscience, University of St. Andrews, Scotland, UK; Department of Biological Sciences, North Dakota State University, Fargo, ND, USA; Max Planck Institute for Ornithology, Seewiesen, Germany; Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK.
Integr Comp Biol. 2014 Oct;54(4):633-44. doi: 10.1093/icb/icu094. Epub 2014 Jul 1.
Whether melanin-based colors honestly signal a bird's condition during the growth of feathers is controversial, and it is unclear if, or how, the physiological processes underlying melanogenesis or the role of the microstructure of feathers in imparting structural color to feathers may be adversely affected by condition. Here, we report results from two experiments designed to measure the effect of condition on expression of eumelanic and pheomelanic coloration in black-capped chickadees (Poecile atricapillus) and zebra finches (Taeniopygia guttata), respectively. In chickadees, we compared feathers of birds affected and unaffected by avian keratin disorder, whereas in zebra finches we compared feathers of controls with feathers of those subjected to an unpredictable food supply during development. In both cases, we found that control birds had brighter feathers (higher total reflectance) and more barbules, but similar densities of melanosomes. In addition, the microstructure of the feathers explained variation in color more strongly than did melanosome density. Together, these results suggest that melanin-based coloration may in part be condition-dependent, but that this may be driven by changes in keratin and feather development, rather than melanogenesis itself. Researchers should be cautious when assigning variation in melanin-based color to melanin alone and microstructure of the feather should be taken into account.
在羽毛生长过程中，基于黑色素的颜色是否能真实反映鸟类的健康状况存在争议，而且目前尚不清楚黑色素生成的生理过程，或者羽毛微观结构在赋予羽毛结构色方面的作用是否会受到健康状况的不利影响。在此，我们报告了两个实验的结果，这两个实验旨在分别测量健康状况对黑顶山雀（Poecile atricapillus）和斑胸草雀（Taeniopygia guttata）中真黑色素和褐黑色素着色表达的影响。在山雀实验中，我们比较了受禽角蛋白紊乱影响和未受影响的鸟类的羽毛，而在斑胸草雀实验中，我们将对照组的羽毛与在发育过程中经历不可预测食物供应的鸟类的羽毛进行了比较。在这两种情况下，我们发现对照组的鸟类羽毛更亮（总反射率更高）且羽小枝更多，但黑素体密度相似。此外，羽毛的微观结构比黑素体密度更能有力地解释颜色变化。综合这些结果表明，基于黑色素的着色可能部分取决于健康状况，但这可能是由角蛋白和羽毛发育的变化驱动的，而不是黑色素生成本身。研究人员在仅将基于黑色素的颜色变化归因于黑色素时应谨慎，并且应考虑羽毛的微观结构。
