通过光谱与视觉模型研究动物体色

Using spectra and visual modeling to study animal coloration

体色是动物进行种内和种间信息交流的重要性状特征。与人类的三基色视觉系统不同,许多动物都具有四面体颜色系统,包括人眼无法探测的紫外光区域。动物体色是动物生态学中的一项重要研究内容,以人类主观角度对动物体色进行描述和分类,可能会导致研究结果的偏差,甚至得出错误结论。该文以赤红山椒鸟(Pericrocotus flammeus)为实例,通过分段光谱分析,对动物体色的色调、色度、亮度以及各波段的亮度进行量化;通过构建先进的动物视觉模型以考虑环境光线的影响和动物视网膜对不同波段光线的敏感度和捕获能力,同时将颜色斑块直观投射在四面体颜色空间和罗宾逊投影中,以量化颜色跨度和空间容量等参数,真正实现从动物的视觉角度分析动物体色。

Animal coloration has many adaptive functions and plays an important role in signal communication both among intra- and interspecies. For example, it has been widely used in mate choice, intrasexual competition, and as aposematic or cryptic coloration in predator avoidance. Many colors and pigments also function in microbial resistance, structural support, photoprotection, and thermoregulation. Differing from human vision, based on RGB system, many other animals have tetrachromatic vision system, which includes the ultraviolet （UV） range that is undetectable by human eyes. Previous studies showed that ultraviolet is important in some species＇ social signaling and communication. Moreover, cone inner segments of most classes of vertebrate contain an oil droplet, which acts as a cut-off filter absorbing wavelengths below a critical value, and transmitting longer wavelengths. Animal and human vision is significantly different in that the classification of color by human standards may be a misleading for measuring animal coloration. Here, we illuminate how to use fiber spectrophotometer to quantify animal coloration, and analyze it by spectra analysis and visual modeling. As an example, we obtained plumage reflectance spectra from male and female scarlet minivets （Pericrocotus flammeus）. This bird species is sexually dimorphic that the males have plumage color in black and red, while the females have grey and yellow accordingly. These plumage colors are typically generated from melanin and carotenoid pigments, which have an effect on antioxidant activity. Analysis of spectra segments provides hue, chroma, brightness and relative brightness of each wave range. Visual modeling maps color patches on tetrahedral color space and Robinson projection, meanwhile, calculates color span and color space volume which describe the color contrast and color diversity, respectively. In visual modeling, ambient light irradiance and spectral sensitivity of animal retinas are included, which provides an objective evaluation of coloration of animal vision.