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.

Department of Biology and Integrated Bioscience Program The University of Akron Akron OH 44325 USA

Department of Polymer Science The University of Akron Akron OH 44325 USA

Department of Psychology Hunter College and the Graduate Center The City University of New York New York NY 10065 USA

Department of Zoology and Laboratory of Ornithology Palacký University Olomouc 77146 Czech Republic

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

School of Chemical Sciences The University of Auckland Private Bag 92019 Auckland New Zealand

Zobrazit více v PubMed

Hunt S, Bennett AT, Cuthill IC, Griffiths R. 1998. Blue tits are ultraviolet tits. Proc. R. Soc. Lond. B 265, 451–455. (10.1098/rspb.1998.0316) DOI

Maia R, D'Alba L, Shawkey MD. 2011. What makes a feather shine? A nanostructural basis for glossy black colours in feathers. Proc. R. Soc. B 278, 1973–1980. (10.1098/rspb.2010.1637) PubMed DOI PMC

Fox H, Vevers G. 1960. The nature of animal colours. London, UK: Sidgwick and Jackson Limited.

Newton I. 1704. Opticks. London, UK: William Innys.

Shawkey MD, Hill GE. 2006. Significance of a basal melanin layer to production of non-iridescent structural plumage color: evidence from an amelanotic Steller's jay (Cyanocitta stelleri). J. Exp. Biol. 209, 1245–1250. (10.1242/jeb.02115) PubMed DOI

Bagnara JT, Fernandez PJ, Fujii R. 2007. On the blue coloration of vertebrates. Pigment Cell Res. 20, 14–26. (10.1111/j.1600-0749.2006.00360.x) PubMed DOI

Kinoshita S. 2008. Structural colors in the realm of nature. Singapore: World Scientific.

D'Alba L, Kieffer L, Shawkey MD. 2012. Relative contributions of pigments and biophotonic nanostructures to natural color production: a case study in budgerigar (Melopsittacus undulatus) feathers. J. Exp. Biol. 215, 1272–1277. (10.1242/jeb.064907) PubMed DOI

Vukusic P, Hallam B, Noyes J. 2007. Brilliant whiteness in ultrathin beetle scales. Science 315, 348 (10.1126/science.1134666) PubMed DOI

Vašíček A. 1960. Optics of thin films. Amsterdam, The Netherlands: North-Holland Pub. Co.

Liu Y, Shigley J, Hurwit K. 1999. Iridescent color of a shell of the mollusk Pinctada margaritifera caused by diffraction. Opt. Express 4, 177–182. (10.1364/OE.4.000177) PubMed DOI

Hegedüs R, Szél G, Horváth G. 2006. Imaging polarimetry of the circularly polarizing cuticle of scarab beetles (Coleoptera: Rutelidae, Cetoniidae). Vis. Res. 46, 2786–2797. (10.1016/j.visres.2006.02.007) PubMed DOI

Rasmussen PV, Dyck J. 2000. Silkiness in brown mink pelts characterized with optical methods. J. Anim. Sci. 78, 1697–1709. PubMed

Vignolini S, Thomas MM, Kolle M, Wenzel T, Rowland A, Rudall PJ, Baumberg JJ, Glover BJ, Steiner U. 2012. Directional scattering from the glossy flower of Ranunculus: how the buttercup lights up your chin. J. R. Soc. Interface 9, 1295–1301. (10.1098/rsif.2011.0759) PubMed DOI PMC

Willmouth FM. 1986. Transparency, translucency and gloss. In Optical properties of polymers (ed. Meeten GH.), pp. 265–334. London, UK: Elsevier Applied Science Publishers.

Hunter RS. 1937. Methods of determining gloss. J. R. Natl Bur. Stand. 18, 19–39. (10.6028/jres.018.006) DOI

Toomey MB, Butler MW, Meadows MG, Taylor LA, Fokidis HB, McGraw KJ. 2010. A novel method for quantifying the glossiness of animals. Behav. Ecol. Sociobiol. 64, 1047–1055. (10.1007/s00265-010-0926-z) DOI

Hauber M. 2014. The book of eggs. Chicago, IL: University of Chicago Press.

Kilner R. 2006. The evolution of egg colour and patterning in birds. Biol. Rev. 81, 383–406. (10.1017/S1464793106007044) PubMed DOI

Fernandez MS, Araya M, Arias JL. 1997. Eggshells are shaped by a precise spatio-temporal arrangement of sequentially deposited macromolecules. Matrix Biol. 16, 13–20. (10.1016/S0945-053X(97)90112-8) PubMed DOI

Cassey P, Thomas GH, Portugal SJ, Maurer G, Hauber ME, Grin T, Lovell PG, Mikšík I. 2012. Why are birds’ eggs colourful? Eggshell pigments co-vary with life-history and nesting ecology among British breeding non-passerine birds. Biol. J. Linn. Soc. 106, 657–672. (10.1111/j.1095-8312.2012.01877.x) DOI

Cassey P, Portugal SJ, Maurer G, Ewen JG, Boulton RL, Hauber ME, Blackburn TM. 2010. Variability in avian eggshell colour: a comparative study of museum eggshells. PLoS ONE 5, e12054 (10.1371/journal.pone.0012054) PubMed DOI PMC

Sorby HC. 1875. On the colouring-matters of the shells of birds’ eggs. Proc. Zool. Soc. Lond. 23, 351–365.

Kennedy G, Vevers H. 1976. A survey of avian eggshell pigments. Comp. Biochem. Physiol. B Comp. Biochem. 55, 117–123. (10.1016/0305-0491(76)90183-8) PubMed DOI

Gorchein A, Lim C, Cassey P. 2009. Extraction and analysis of colourful eggshell pigments using HPLC and HPLC/electrospray ionization tandem mass spectrometry. Biomed. Chromatogr. 23, 602–606. (10.1002/bmc.1158) PubMed DOI

Vukusic P, Sambles JR. 2003. Photonic structures in biology. Nature 424, 852–855. (10.1038/nature01941) PubMed DOI

Grégoire C. 1957. Topography of the organic components in mother-of-pearl. J. Biophys. Biochem. Cytol. 3, 797–808. (10.1083/jcb.3.5.797) PubMed DOI PMC

Hanley D, Stoddard MC, Cassey P, Brennan PLR. 2013. Eggshell conspicuousness in ground nesting birds: do conspicuous eggshells signal nest location to conspecifics? Avian Biol. Res. 6, 147–156. (10.3184/175815513X13617279883973) DOI

Mikhailov KE, Ornithologists’ Club B. 1997. Avian eggshells: an atlas of scanning electron micrographs. Newbury, British Ornithologists’ Club Occasional Publications, No. 3. The Nature Conservancy Bureau Limited.

Rose-Martel M, Du J, Hincke MT. 2012. Proteomic analysis provides new insight into the chicken eggshell cuticle. J. Proteomics 75, 2697–2706. (10.1016/j.jprot.2012.03.019) PubMed DOI

Dennis JE, Xiao S-Q, Agarwal M, Fink DJ, Heuer AH, Caplan AI. 1996. Microstructure of matrix and mineral components of eggshells from white leghorn chickens (Gallus gallus). J. Morphol. 228, 287–306. (10.1002/(SICI)1097-4687(199606)228:3<287::AID-JMOR2>3.0.CO;2-#) PubMed DOI

Wellman-Labadie O, Picman J, Hincke MT. 2008. Antimicrobial activity of the Anseriform outer eggshell and cuticle. Comp. Biochem. Physiol. B Biochem. Mol. Biol. 149, 640–649. (10.1016/j.cbpb.2008.01.001) PubMed DOI

Baker J, Balch D. 1962. A study of the organic material of hen's-egg shell. Biochem. J. 82, 352. PubMed PMC

Deeming D. 1987. Effect of cuticle removal on the water vapour conductance of egg shells of several species of domestic bird. Br. Poultr. Sci. 28, 231–237. (10.1080/00071668708416957) DOI

D'Alba L, Jones DN, Badawy HT, Eliason CM, Shawkey MD. 2014. Antimicrobial properties of a nanostructured eggshell from a compost-nesting bird. J. Exp. Biol. 217, 1116–1121. (10.1242/jeb.098343) PubMed DOI

Peebles E, Brake J, Gildersleeve R. 1987. Effects of eggshell cuticle removal and incubation humidity on embryonic development and hatchability of broilers. Poultr. Sci. 66, 834–840. (10.3382/ps.0660834) PubMed DOI

Richards P, Deeming DC. 2001. Correlation between shell colour and ultrastructure in pheasant eggs. Br. Poultr. Sci. 42, 338–343. (10.1080/00071660120055304) PubMed DOI

Samiullah S, Roberts J. 2013. Protoporphyrin IX in shell and cuticle of brown shelled eggs. In 24th Annual Australian Poultry Science Symp., Sydney, Australia, 17–20 February, pp. 260–263. Poultry Research Foundation.

Riehl C, Jara L. 2009. Natural history and reproductive biology of the communally breeding greater ani (Crotophaga major) at Gatún Lake, Panama. Wilson J. Ornithol. 121, 679–687. (10.1676/09-017.1) DOI

Cassey P, Maurer G, Duval C, Ewen JG, Hauber ME. 2010. Impact of time since collection on avian eggshell color: a comparison of museum and fresh egg specimens. Behav. Ecol. Sociobiol. 64, 1711–1720. (10.1007/s00265-010-1027-8) DOI

McNamara ME. 2013. The taphonomy of colour in fossil insects and feathers. Palaeontology 56, 557–575. (10.1111/pala.12044) DOI

Maurer G, Cassey P. 2011. Evaluation of a glossmeter for studying the surface appearance of avian eggs. J. Ornithol. 152, 209–212. (10.1007/s10336-010-0600-2) DOI

Maia R, Eliason CM, Bitton P-P, Doucet SM, Shawkey MD. 2013. pavo: an R package for the analysis, visualization and organization of spectral data. Methods Ecol. Evol. 4, 906–913.

R Core Team. 2013. R: a language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing.

Nečas D, Klapetek P. 2012. Gwyddion: an open-source software for SPM data analysis. Centr. Eur. J. Phys. 10, 181–188. (10.2478/s11534-011-0096-2) DOI

Bragg W. 1924. The refractive indices of calcite and aragonite. Proc. R. Soc. Lond. A 105, 370–386. (10.1098/rspa.1924.0026) DOI

Stamm RF, Garcia ML, Fuchs JJ. 1977. The optical properties of human hair I. Fundamental considerations and goniophotometer curves. J. Soc. Cosmet. Chem. 28, 571.

Stavenga DG, Tinbergen J, Leertouwer HL, Wilts BD. 2011. Kingfisher feathers—colouration by pigments, spongy nanostructures and thin films. J. Exp. Biol. 214, 3960–3967. (10.1242/jeb.062620) PubMed DOI

Noh H, Liew SF, Saranathan V, Mochrie SG, Prum RO, Dufresne ER, Cao H. 2010. How noniridescent colors are generated by quasi-ordered structures of bird feathers. Adv. Mater. 22, 2871–2880. (10.1002/adma.200903699) PubMed DOI

Osorio D, Ham A. 2002. Spectral reflectance and directional properties of structural coloration in bird plumage. J. Exp. Biol. 205, 2017–2027. PubMed

Igic B, et al. 2010. Detecting pigments from colourful eggshells of extinct birds. Chemoecology 20, 43–48. (10.1007/s00049-009-0038-2) DOI

Board R, Perrott H, Love G, Scott V. 1984. The phosphate-rich cover on the eggshells of grebes (Aves: Podicipitiformes). J. Zool. 203, 329–343. (10.1111/j.1469-7998.1984.tb02336.x) DOI

Board RG, Perrott HR, Love G, Seymour RS. 1982. A novel pore system in the eggshells of the mallee fowl, Leipoa ocellata. J. Exp. Zool. 220, 131–134. (10.1002/jez.1402200118) DOI

Tullett S, Board R, Love G, Perrott H, Scott V. 1976. Vaterite deposition during eggshell formation in the cormorant, gannet and shag, and in ‘shell-less’ eggs of the domestic fowl. Acta Zool. 57, 79–87. (10.1111/j.1463-6395.1976.tb00213.x) DOI

Handford P, Mares MA. 1985. The mating systems of ratites and tinamous: an evolutionary perspective. Biol. J. Linn. Soc. 25, 77–104. (10.1111/j.1095-8312.1985.tb00387.x) DOI

Fernández GJ, Reboreda JC. 1998. Effects of clutch size and timing of breeding on reproductive success of greater rheas. Auk 115, 340–348. (10.2307/4089192) DOI

Brennan PLR. 2010. Clutch predation in great tinamous Tinamus major and implications for the evolution of egg color. J. Avian Biol. 41, 419–426. (10.1111/j.1600-048X.2010.04999.x) DOI

Hanley D, Doucet SM, Dearborn DC. 2010. A blackmail hypothesis for the evolution of conspicuous egg coloration in birds. Auk 127, 453–459. (10.1525/auk.2009.09090) DOI

Brennan PL. 2009. Incubation in great tinamou (Tinamus major). Wilson J. Ornithol. 121, 506–511. (10.1676/08-073.1) DOI

Bikerman J. 1950. Sliding of drops from surfaces of different roughnesses. J. Colloid Sci. 5, 349–359. (10.1016/0095-8522(50)90059-6) DOI

Maurer G, Portugal SJ, Hauber ME, Mikšík I, Russell DG, Cassey P. 2014. First light for avian embryos: eggshell thickness and pigmentation mediate variation in development and UV exposure in wild bird eggs. Funct. Ecol. (10.1111/1365-2435.12314) DOI

Highly virulent avian brood-parasitic species show elevated embryonic metabolic rates at specific incubation stages compared to less virulent and non-parasitic species

Variation in multicomponent recognition cues alters egg rejection decisions: a test of the optimal acceptance threshold hypothesis

Dynamic egg color mimicry

Eggshell pigment composition covaries with phylogeny but not with life history or with nesting ecology traits of British passerines

Nature's Palette: Characterization of Shared Pigments in Colorful Avian and Mollusk Shells

The cuticle modulates ultraviolet reflectance of avian eggshells

Not so colourful after all: eggshell pigments constrain avian eggshell colour space