title: A nanostructural basis for gloss of avian eggshells.
abstract: The role of pigments in generating the colour and maculation of birds' eggs is well characterized, whereas the effects of the eggshell's nanostructure on the visual appearance of eggs are little studied. Here, we examined the nanostructural basis of glossiness of tinamou eggs. Tinamou eggs are well known for their glossy appearance, but the underlying mechanism responsible for this optical effect is unclear. Using experimental manipulations in conjunction with angle-resolved spectrophotometry, scanning electron microscopy, atomic force microscopy and chemical analyses, we show that the glossy appearance of tinamou eggshells is produced by an extremely smooth cuticle, composed of calcium carbonate, calcium phosphate and, potentially, organic compounds such as proteins and pigments. Optical calculations corroborate surface smoothness as the main factor producing gloss. Furthermore, we reveal the presence of weak iridescence on eggs of the great tinamou (Tinamus major), an optical effect never previously documented for bird eggs. These data highlight the need for further exploration into the nanostructural mechanisms for the production of colour and other optical effects of avian eggshells.
authors.affiliation: Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325, USA brani.igic@gmail.com.
authors.forename: Branislav
authors.initials: B
authors.lastname: Igic
authors.affiliation: Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325, USA.
authors.forename: Daphne
authors.initials: D
authors.lastname: Fecheyr-Lippens
authors.affiliation: Department of Polymer Science, The University of Akron, Akron, OH 44325, USA.
authors.forename: Ming
authors.initials: M
authors.lastname: Xiao
authors.affiliation: School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
authors.forename: Andrew
authors.initials: A
authors.lastname: Chan
authors.affiliation: Department of Zoology and Laboratory of Ornithology, Palacký University, Olomouc 77146, Czech Republic.
authors.forename: Daniel
authors.initials: D
authors.lastname: Hanley
authors.affiliation: Organismic and Evolutionary Biology Graduate Program, Department of Psychology, University of Massachusetts Amherst, Amherst, MA 01003, USA Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA.
authors.forename: Patricia R L
authors.initials: PR
authors.lastname: Brennan
authors.affiliation: Department of Zoology and Laboratory of Ornithology, Palacký University, Olomouc 77146, Czech Republic.
authors.forename: Tomas
authors.initials: T
authors.lastname: Grim
authors.affiliation: School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
authors.forename: Geoffrey I N
authors.initials: GI
authors.lastname: Waterhouse
authors.affiliation: Department of Psychology, Hunter College and the Graduate Center, The City University of New York, New York, NY 10065, USA.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Hauber
authors.affiliation: Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Shawkey
mesh_terms: D000818:Animals; D001717:Birds; D002119:Calcium Carbonate / Q000378:metabolism*; D002130:Calcium Phosphates / Q000378:metabolism*; D004527:Egg Proteins / Q000378:metabolism*; D049329:Nanostructures / Q000648:ultrastructure*; D010063:Ovum / Q000378:metabolism / Q000648:ultrastructure; D010858:Pigmentation / Q000502:physiology*
chemical_list: D002130:Calcium Phosphates; D004527:Egg Proteins; C015753:chorion proteins; C020243:calcium phosphate; D002119:Calcium Carbonate
keywords: eggshell; gloss; iridescence; nanostructure; structural colour; tinamou