Oil droplets of bird eyes: Microlenses acting as spectral filters

Doekele G. Stavenga*, Bodo D. Wilts

*Bijbehorende auteur voor dit werk

    OnderzoeksoutputAcademicpeer review

    40 Citaten (Scopus)

    Samenvatting

    An important component of the cone photoreceptors of bird eyes is the oil droplets located in front of the visual-pigment-containing outer segments. The droplets vary in colour and are transparent, clear, pale or rather intensely yellow or red owing to various concentrations of carotenoid pigments. Quantitative modelling of the filter characteristics using known carotenoid pigment spectra indicates that the pigments' absorption spectra are modified by the high concentrations that are present in the yellow and red droplets. The high carotenoid concentrations not only cause strong spectral filtering but also a distinctly increased refractive index at longer wavelengths. The oil droplets therefore act as powerful spherical microlenses, effectively channelling the spectrally filtered light into the photoreceptor's outer segment, possibly thereby compensating for the light loss caused by the spectral filtering. The spectral filtering causes narrow-band photoreceptor spectral sensitivities, which are well suited for spectral discrimination, especially in birds that have feathers coloured by carotenoid pigments.

    Originele taal-2English
    Artikelnummer20130041
    Aantal pagina's8
    TijdschriftPhilosophical Transactions of the Royal Society of London. Series B: Biological Sciences
    Volume369
    Nummer van het tijdschrift1636
    DOI's
    StatusPublished - 19-feb.-2014

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