TY - JOUR
T1 - A complex carotenoid palette tunes avian colour vision
AU - Toomey, Matthew B.
AU - Collins, Aaron M.
AU - Frederiksen, Rikard
AU - Cornwall, M. Carter
AU - Timlin, Jerilyn A.
AU - Corbo, Joseph C.
N1 - Publisher Copyright:
© 2015 The Author(s) Published by the Royal Society. All rights reserved.
PY - 2015/10/6
Y1 - 2015/10/6
N2 - The brilliantly coloured cone oil droplets of the avian retina function as long-pass cut-off filters that tune the spectral sensitivity of the photoreceptors and are hypothesized to enhance colour discrimination and improve colour constancy. Although it has long been known that these droplets are pigmented with carotenoids, their precise composition has remained uncertain owing to the technical challenges of measuring these very small, dense and highly refractile optical organelles. In this study, we integrated results from high-performance liquid chromatography, hyperspectral microscopy and microspectrophotometry to obtain a comprehensive understanding of oil droplet carotenoid pigmentation in the chicken (Gallus gallus). We find that each of the four carotenoid-containing droplet types consists of a complex mixture of carotenoids, with a single predominant carotenoid determining the wavelength of the spectral filtering cut-off. Consistent with previous reports, we find that the predominant carotenoid type in the oil droplets of long-wavelength-sensitive, medium-wavelength-sensitive and short-wavelength-sensitive type 2 cones are astaxanthin, zeaxanthin and galloxanthin, respectively. In addition, the oil droplet of the principal member of the double cone contains a mixture of galloxanthin and two hydroxycarotenoids (lutein and zeaxanthin). Short-wavelength-absorbing apocarotenoids are present in all of the droplet types, providing filtering of light in a region of the spectrum where filtering by hydroxy- and ketocarotenoids may be incomplete. Thus, birds rely on a complex palette of carotenoid pigmentswithin their cone oil droplets to achieve finely tuned spectral filtering.
AB - The brilliantly coloured cone oil droplets of the avian retina function as long-pass cut-off filters that tune the spectral sensitivity of the photoreceptors and are hypothesized to enhance colour discrimination and improve colour constancy. Although it has long been known that these droplets are pigmented with carotenoids, their precise composition has remained uncertain owing to the technical challenges of measuring these very small, dense and highly refractile optical organelles. In this study, we integrated results from high-performance liquid chromatography, hyperspectral microscopy and microspectrophotometry to obtain a comprehensive understanding of oil droplet carotenoid pigmentation in the chicken (Gallus gallus). We find that each of the four carotenoid-containing droplet types consists of a complex mixture of carotenoids, with a single predominant carotenoid determining the wavelength of the spectral filtering cut-off. Consistent with previous reports, we find that the predominant carotenoid type in the oil droplets of long-wavelength-sensitive, medium-wavelength-sensitive and short-wavelength-sensitive type 2 cones are astaxanthin, zeaxanthin and galloxanthin, respectively. In addition, the oil droplet of the principal member of the double cone contains a mixture of galloxanthin and two hydroxycarotenoids (lutein and zeaxanthin). Short-wavelength-absorbing apocarotenoids are present in all of the droplet types, providing filtering of light in a region of the spectrum where filtering by hydroxy- and ketocarotenoids may be incomplete. Thus, birds rely on a complex palette of carotenoid pigmentswithin their cone oil droplets to achieve finely tuned spectral filtering.
KW - Carotenoid
KW - Hyperspectral microscopy
KW - Microspectrophotometry
KW - Vision
UR - http://www.scopus.com/inward/record.url?scp=84945913634&partnerID=8YFLogxK
U2 - 10.1098/rsif.2015.0563
DO - 10.1098/rsif.2015.0563
M3 - Article
C2 - 26446559
AN - SCOPUS:84945913634
SN - 1742-5689
VL - 12
JO - Journal of the Royal Society Interface
JF - Journal of the Royal Society Interface
IS - 111
M1 - 20150563
ER -