Meeting Abstract

33.1  Sunday, Jan. 5 08:00  The ontogeny of an iridescent nanostructure composed of hollow melanosomes SHAWKEY, MD*; D’ALBA, L; XIAO, M; BUCHHOLZ, R; University of Akron; University of Akron; University of Akron; University of Mississippi shawkey@uakron.edu

Iridescent feathers are among the most colorful objects in nature and are model systems for the evolution of sexually selected traits. Their colors are produced by coherent light scattering from linear or crystalline arrangements of melanosomes (melanin-containing organelles). Hollow melanosomes, an evolutionary innovation largely restricted to birds, contain an optically powerful combination of high and low refractive indices (from the melanin and air, respectively) that enables production of brighter and more saturated colors than solid melanosomes. However, despite their significance to avian color evolution and potential utility as optical biomaterials, little is known about the ontogeny of either the melanosomes themselves or the nanostructures they comprise. We used light and electron microscopy to characterize nanostructural development in regenerating feathers of wild turkeys, a species with iridescent color produced by a hexagonally close-packed array of hollow melanosomes. We found that melanosomes form as solid bodies in melanocytes. Later in development, largely after placement in developing barbules, their interiors dissolve and leave hollow cores. These now hollow melanosomes are initially disorganized in the barbule, but become close-packed as they are trapped between two layers of polymerizing keratin. These data thus provide further evidence that structurally colored tissues are self-assembled and represent novel pathways of development that could provide inspiration for new materials.