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Structural color production by constructive reflection from ordered collagen arrays in a bird (Philepitta castanea:
Richard O Prum1, Randall L Morrison2, Gary R Ten Eyck1
1Department of Systematics and Ecology, and Museum of Natural History, The University of Kansas, Lawrence, Kansas 66045-2454.
Abstract:
Ordered hexagonal arrays of parallel collagen fibers produce the brilliant green structural color of the fleshy, supraorbital caruncles of male Velvet Asity (Philepitta castanea; Aves: Eurylaimidae). The collagen arrays are organized in larger macrofibrils that are packed irregularly within cone-shaped papillae that cover the surface of the caruncle. The color of the caruncle conforms closely to the wavelengths predicted by applying Bragg's Law of constructive reflection to measurements of the size and spatial organization of the collagen arrays. These observations constitute a novel mechanism of structural color production in animals. These collagen arrays are convergently similar to the smaller, highly structured collagen arrays in the mammalian cornea, which exploit the same physical mechanism to produce optical transparency. © 1994 Wiley-Liss, Inc.
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