Meeting Abstract
95.3 Thursday, Jan. 7 Evolutionary Photonics Of Avian Amorphous Color-Producing Nanostructures SARANATHAN, V.*; PRUM, R. O.; Department of Ecology and Evolutionary Biology, Peabody Museum of Natural History, and Center for Research on Interface Structures and Phenomena (CRISP), Yale University, New Haven, CT; Department of Ecology and Evolutionary Biology, Peabody Museum of Natural History, and Center for Research on Interface Structures and Phenomena (CRISP), Yale University, New Haven, CT Vinodkumar.Saranathan@yale.edu
Non-iridescent structural colors in feather barbs form an important aspect of the avian phenotype and are frequently used in sexual and social communication. They are produced by quasi-ordered/amorphous photonic (color-producing) nanostructures of beta-keratin and air. In order to understand their biological function and evolution, however, we need to physically characterize organismal structural color production using a precise 3D knowledge of the nanostructure. However, current techniques like SEM/TEM do not provide 3D data. We used Small Angle X-ray Scattering (SAXS) to characterize the spatial organization of avian barb photonic nanostructures. We collected SAXS data from ~210 distinct structurally colored plumage patches belonging to ~150 avian species at the Advanced Photon Source, Argonne National Labs. We use single light scattering theory to predict the optical reflectance directly from the SAXS structural information, which are not only congruent with reflectance measurements, but offer substantial improvements over 2D-Fourier analysis of TEMs. Phylogenetic analysis suggests that barb structural colors have indpendently evolved at least 40 times across the avian phylogeny. Using SAXS, we are also reliably able to distinguish between the two classes of barb nanostructures–spheres and channels. We discuss these results in light of the putative self-assembly of these avian barb nanostructures through phase separation kinetics of beta-keratin from the cellular cytoplasm.
