title: Characterization of visual pigments, oil droplets, lens and cornea in the whooping crane Grus americana.
abstract: Vision has been investigated in many species of birds, but few studies have considered the visual systems of large birds and the particular implications of large eyes and long-life spans on visual system capabilities. To address these issues we investigated the visual system of the whooping crane Grus americana (Gruiformes, Gruidae), which is one of only two North American crane species. It is a large, long-lived bird in which UV sensitivity might be reduced by chromatic aberration and entrance of UV radiation into the eye could be detrimental to retinal tissues. To investigate the whooping crane visual system we used microspectrophotometry to determine the absorbance spectra of retinal oil droplets and to investigate whether the ocular media (i.e. the lens and cornea) absorb UV radiation. In vitro expression and reconstitution was used to determine the absorbance spectra of rod and cone visual pigments. The rod visual pigments had wavelengths of peak absorbance (λmax) at 500 nm, whereas the cone visual pigment λmax values were determined to be 404 nm (SWS1), 450 nm (SWS2), 499 nm (RH2) and 561 nm (LWS), similar to other characterized bird visual pigment absorbance values. The oil droplet cut-off wavelength (λcut) values similarly fell within ranges recorded in other avian species: 576 nm (R-type), 522 nm (Y-type), 506 nm (P-type) and 448 nm (C-type). We confirm that G. americana has a violet-sensitive visual system; however, as a consequence of the λmax of the SWS1 visual pigment (404 nm), it might also have some UV sensitivity.
authors.affiliation: Department of Biology, University of South Dakota, Vermillion, SD 57069, USA Megan.Porter@usd.edu.
authors.forename: Megan L
authors.initials: ML
authors.lastname: Porter
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
authors.forename: Alexandra C N
authors.initials: AC
authors.lastname: Kingston
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: McCready
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
authors.forename: Evan G
authors.initials: EG
authors.lastname: Cameron
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Hofmann
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
authors.forename: Lauren
authors.initials: L
authors.lastname: Suarez
authors.affiliation: USGS Pautuxent Wildlife Research Center, Laurel, MD 20708, USA.
authors.forename: Glenn H
authors.initials: GH
authors.lastname: Olsen
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Cronin
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
authors.forename: Phyllis R
authors.initials: PR
authors.lastname: Robinson
mesh_terms: D000818:Animals; D001717:Birds / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003315:Cornea / Q000502:physiology / Q000528:radiation effects; D007908:Lens, Crystalline / Q000502:physiology / Q000528:radiation effects; D066292:Lipid Droplets / Q000378:metabolism*; D015591:Microspectrophotometry; D009799:Ocular Physiological Phenomena; D055355:Opsins / Q000032:analysis*; D012160:Retina / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D055355:Opsins
keywords: Ocular media; Oil droplets; Opsin; Visual pigment; Whooping crane