Meeting Abstract

P1.81  Tuesday, Jan. 4  What makes a feather shine? A nanostructural basis for glossy black colors in feathers MAIA, R.*; D’ALBA, L.A.; SHAWKEY, M.D.; The University of Akron; The University of Akron; The University of Akron rm72@zips.uakron.edu

Colors in feathers are produced by pigments, or nanostructurally organized tissues that interact with light. One of the simplest nanostructures is a single layer of keratin overlying a linearly organized layer of melanosomes that creates iridescent colors of feather barbules through thin-film interference. Recently, it has been hypothesized that glossy (i.e. high specular reflectance) black feathers may be evolutionarily intermediate between matte black and iridescent feathers, and thus have a smooth keratin layer that produces gloss, but not the layered organization of melanosomes needed for iridescence. However, the morphological bases of glossiness remain unknown. Here we combine theoretical and empirical approaches to identify the mechanisms of gloss production in feathers. Thin-film models predicted that glossy spectra would result from a keratin layer 110-180nm thick, and a melanin layer greater than 115 nm thick. Transmission electron microscopy data show that nanostructure of glossy barbules falls well within that range, but that of matte barbules does not. Further, glossy barbules had a thinner and more regular keratin cortex, as well as a more continuous underlying melanin layer, than matte barbules. Thus, this quasi-ordered nanostructure appears to be morphologically intermediate between that of matte black and iridescent feathers, and what is perceived as gloss in its reflectance is in fact weak iridescent color.