Iridescent plumage in satin bowerbirds: structure, mechanisms and nanostructural predictors of individual variation in colour
Iridescent plumage in satin bowerbirds: structure, mechanisms and nanostructural predictors of individual variation in colour
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DOI：
10.1242/jeb.01988
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发表时间：
2006-01-01
影响因子：
2.8
通讯作者：
Montgomerie, R
中科院分区：
文献类型：
--
作者：
Doucet, SM;Shawkey, MD;Montgomerie, R
彩虹色是由不同折射率材料的交替层的光波相干散射产生的。在鸟类中，当光线从角蛋白、黑色素和空气的交替层散射时，羽毛小羽就会产生彩虹色。这些层的结构和组织，以及因此具有不同类型羽毛虹彩的鸟类的外观，差异很大。不同类型的虹彩颜色之间的一个主要区别在于它们是由单对层还是由多对层产生。多层虹彩（例如蜂鸟所表现出的虹彩）已经得到了相对较好的表征，但单层虹彩直到最近才被成功建模。在这里，我们使用电子显微镜、光谱测定法和薄膜光学模型来研究成年雄性缎纹园丁鸟 Ptilonorhynchus violaceus 小的光泽、紫外蓝色虹彩羽毛颜色。成年男性的扁平小羽枝由表面角蛋白层组成，其上覆盖有几个颗粒厚的黑色素层。基于角蛋白层厚度及其两个相关界面（空气/角蛋白和角蛋白/黑色素）的薄膜模型生成与测量光谱紧密匹配的预测反射光谱。此外，从该模型预测的色调与测量的色调呈正相关。正如我们的薄膜模型所预测的那样，随着入射角和反射角的增加，测量的色调会向较短的波长转变。此外，我们发现小枝纳米结构的个体差异可以预测色调和紫外色度的测量变化。因此，我们表征了缎纹园丁鸟小羽枝的微观结构，揭示了这些小羽枝中产生紫外线虹彩的机制，并提供了虹彩羽毛颜色个体差异的纳米结构基础的第一个证据。
Iridescence is produced by coherent scattering of light waves from alternating layers of materials of different refractive indices. In birds, iridescent colours are produced by feather barbules when light is scattered from alternating layers of keratin, melanin and air. The structure and organization of these layers, and hence the appearance of bird species with different types of plumage iridescence, varies extensively. One principal distinction between different types of iridescent colours is whether they are produced by a single pair of layers or by multiple pairs of layers. Multi-layer iridescence, such as that displayed by hummingbirds, has been relatively well characterized, but single-layer iridescence has only recently been modeled successfully. Here we use electron microscopy, spectrometry and thin-film optical modeling to investigate the glossy, ultraviolet-blue iridescent plumage colouration of adult male satin bowerbirds Ptilonorhynchus violaceus minor. The flattened barbules of adult males are composed of a superficial keratin layer overlying a melanin layer that is several granules thick. A thin-film model based on the thickness of the keratin layer and its two associated interfaces (air/keratin and keratin/melanin) generates predicted reflectance spectra that closely match measured spectra. In addition, hues predicted from this model are positively correlated with measured hues. As predicted from our thin-film model, measured hues shifted to shorter wavelengths at increasing angles of incidence and reflectance. Moreover, we found that individual variation in barbule nanostructure can predict measured variation in both hue and UV-chroma. Thus, we have characterized the microstructure of satin bowerbird barbules, uncovered the mechanisms responsible for producing ultraviolet iridescence in these barbules, and provided the first evidence of a nanostructural basis for individual variation in iridescent plumage colour.