Yoshioka S, Nakano T, Nozue Y, Kinoshita S
Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan.
J R Soc Interface. 2008 Apr 6;5(21):457-64. doi: 10.1098/rsif.2007.1268.
Colour patterns of animals' bodies are usually produced by the spatial distribution of pigments with different colours. However, some animals use the spatial variation of colour-producing microstructures. We have studied one distinctive example of such structurally produced colour patterns, the wing of the Madagascan sunset moth, to clarify the physical rules that underlie the colour variation. It is known that the iridescent wing scale of the sunset moth has the alternate air-cuticle multilayer structure that causes optical interference. The microscopic and optical investigations of various parts of the wing have confirmed that the thickness of the cuticle layers within the scale largely varies to produce the colour pattern. However, it varies in very different ways between the dorsal and ventral sides of the hind wing; the thickness gradually varies on the dorsal side from scale to scale, while the abrupt changes are found on the ventral side to form distinctive borders between differently coloured areas. It is also revealed that an unusual coloration mechanism is involved in the green part of the ventral hind wing: the colour is caused by higher order optical interference of the highly non-ideal multilayer structure. The physical mechanism of the colour pattern formation is briefly discussed with the several mathematical models proposed so far.
动物身体的颜色图案通常由不同颜色色素的空间分布产生。然而，一些动物利用产生颜色的微观结构的空间变化。我们研究了这种由结构产生的颜色图案的一个独特例子——马达加斯加日落蛾的翅膀，以阐明其颜色变化背后的物理规律。众所周知，日落蛾的虹彩翅鳞片具有交替的空气 - 角质层多层结构，会引起光学干涉。对翅膀各个部分的微观和光学研究证实，鳞片内角质层的厚度变化很大，从而产生颜色图案。然而，后翅的背侧和腹侧变化方式非常不同；背侧鳞片之间的厚度逐渐变化，而腹侧则有突然变化，在不同颜色区域之间形成明显的边界。研究还表明，后翅腹侧绿色部分涉及一种不寻常的着色机制：颜色是由高度非理想多层结构的高阶光学干涉引起的。结合目前提出的几个数学模型，简要讨论了颜色图案形成的物理机制。
