Open AccessFine structural dependence of ultraviolet reflections in the King Penguin beak horn
Author(s) -
Dresp Birgitta,
Langley Keith
Publication year - 2006
Publication title -
the anatomical record part a: discoveries in molecular, cellular, and evolutionary biology
Language(s) - English
Resource type - Journals
eISSN - 1552-4892
pISSN - 1552-4884
DOI - 10.1002/ar.a.20314
Subject(s) - ultraviolet , beak , wavelength , optics , photonic crystal , photonics , signal (programming language) , materials science , optoelectronics , ultraviolet light , reflectivity , biology , physics , computer science , ecology , programming language
The visual perception of many birds extends into the near‐ultraviolet (UV) spectrum and ultraviolet is used by some to communicate. The beak horn of the King Penguin ( Aptenodytes patagonicus ) intensely reflects in the ultraviolet and this appears to be implicated in partner choice. In a preliminary study, we recently demonstrated that this ultraviolet reflectance has a structural basis, resulting from crystal‐like photonic structures, capable of reflecting in the near‐UV. The present study attempted to define the origin of the photonic elements that produce the UV reflectance and to better understand how the UV signal is optimized by their fine structure. Using light and electron microscopic analysis combined with new spectrophotometric data, we describe here in detail the fine structure of the entire King Penguin beak horn in addition to that of its photonic crystals. The data obtained reveal a one‐dimensional structural periodicity within this tissue and demonstrate a direct relationship between its fine structure and its function. In addition, they suggest how the photonic structures are produced and how they are stabilized. The measured lattice dimensions of the photonic crystals, together with morphological data on its composition, permit predictions of the wavelength of reflected light. These correlate well with experimentally observed values. The way the UV signal is optimized by the fine structure of the beak tissue is discussed with regard to its putative biological role. © 2006 Wiley‐Liss, Inc.