Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013, USA.
J R Soc Interface. 2013 Mar 20;10(83):20121065. doi: 10.1098/rsif.2012.1065. Print 2013 Jun 6.
Many animals extract, synthesize and refine chemicals for colour display, where a range of compounds and structures can produce a diverse colour palette. Feather colours, for example, span the visible spectrum and mostly result from pigments in five chemical classes (carotenoids, melanins, porphyrins, psittacofulvins and metal oxides). However, the pigment that generates the yellow colour of penguin feathers appears to represent a sixth, poorly characterized class of feather pigments. This pigment class, here termed 'spheniscin', is displayed by half of the living penguin genera; the larger and richer colour displays of the pigment are highly attractive. Using Raman and mid-infrared spectroscopies, we analysed yellow feathers from two penguin species (king penguin, Aptenodytes patagonicus; macaroni penguin, Eudyptes chrysolophus) to further characterize spheniscin pigments. The Raman spectrum of spheniscin is distinct from spectra of other feather pigments and exhibits 17 distinctive spectral bands between 300 and 1700 cm(-1). Spectral bands from the yellow pigment are assigned to aromatically bound carbon atoms, and to skeletal modes in an aromatic, heterocyclic ring. It has been suggested that the penguin pigment is a pterin compound; Raman spectra from yellow penguin feathers are broadly consistent with previously reported pterin spectra, although we have not matched it to any known compound. Raman spectroscopy can provide a rapid and non-destructive method for surveying the distribution of different classes of feather pigments in the avian family tree, and for correlating the chemistry of spheniscin with compounds analysed elsewhere. We suggest that the sixth class of feather pigments may have evolved in a stem-lineage penguin and endowed modern penguins with a costly plumage trait that appears to be chemically unique among birds.
许多动物提取、合成和精炼用于显色的化学物质，其中一系列化合物和结构可以产生多样化的色彩调色板。例如，羽毛颜色涵盖了可见光谱，主要来自五类化学物质（类胡萝卜素、黑色素、卟啉、鹦鹉色素和金属氧化物）的色素。然而，产生企鹅羽毛黄色的色素似乎代表了第六种、特征描述较差的羽毛色素类别。这种色素类别，在这里被称为“spheniscin”，由一半现存的企鹅属展示；这种色素较大且丰富的色彩展示极具吸引力。我们使用拉曼和中红外光谱分析了来自两种企鹅物种（王企鹅，Aptenodytes patagonicus；马可罗尼企鹅，Eudyptes chrysolophus）的黄色羽毛，以进一步表征 spheniscin 色素。spheniscin 的拉曼光谱与其他羽毛色素的光谱不同，在 300 到 1700 厘米(-1)之间有 17 个独特的光谱带。黄色色素的光谱带归因于芳香结合的碳原子，以及芳香杂环的骨架模式。有人认为，企鹅色素是一种蝶呤化合物；黄色企鹅羽毛的拉曼光谱与之前报道的蝶呤光谱大致一致，尽管我们尚未将其与任何已知化合物匹配。拉曼光谱可以提供一种快速且非破坏性的方法，用于调查不同类别羽毛色素在鸟类系统发育中的分布，并将 spheniscin 的化学性质与其他地方分析的化合物相关联。我们认为，第六类羽毛色素可能在一个主干线企鹅中进化，并赋予现代企鹅一种昂贵的羽毛特征，这种特征在鸟类中似乎是化学上独一无二的。
