Male Lawes’s Parotia,a bird of paradise,use the highly directional reflection of the structurally colored,brilliant-silvery occipital feathers in their courtship display.As in other birds,the structural coloration is...Male Lawes’s Parotia,a bird of paradise,use the highly directional reflection of the structurally colored,brilliant-silvery occipital feathers in their courtship display.As in other birds,the structural coloration is produced by ordered melanin pigmentation.The barbules of the Parotia’s occipital feathers,with thickness,3 μm,contain 6–7 layers of densely packed melanin rodlets(diameter,0.25 μm,length,2 μm).The effectively,0.2 μm thick melanin layers separated by,0.2 μm thick keratin layers create a multilayer interference reflector.Reflectance measurements yielded peak wavelengths in the near-infrared at,1.3 μm,i.e.,far outside the visible wavelength range.With the Jamin-Lebedeff interference microscopy method recently developed for pigmented media,we here determined the refractive index of the intact barbules.We thus derived the wavelength dependence of the refractive index of the barbules’melanin to be 1.7–1.8 in the visible wavelength range.Implementing the anatomical and refractive index data in an optical multilayer model,we calculated the barbules’reflectance,transmittance and absorptance spectra,thereby confirming measured spectra.展开更多
Jamin–Lebedeff polarizing interference microscopy is a classical method for determining the refractive index and thickness of transparent tissues.Here,we extend the application of this method to pigmented,absorbing b...Jamin–Lebedeff polarizing interference microscopy is a classical method for determining the refractive index and thickness of transparent tissues.Here,we extend the application of this method to pigmented,absorbing biological tissues,based on a theoretical derivation using Jones calculus.This novel method is applied to the wings of the American Rubyspot damselfly,Hetaerina americana.The membranes in the red-colored parts of the damselfly’s wings,with a thickness of 2.5 μm,contain a pigment with maximal absorption at 490 nm and a peak absorbance coefficient of 0.7 μm^(-1).The high pigment density causes a considerable and anomalous dispersion of the refractive index.This result can be quantitatively understood from the pigment absorbance spectrum by applying the Kramers–Kronig dispersion relations.Measurements of the spectral dependence of the refractive index and the absorption are valuable for gaining quantitative insight into how the material properties of animal tissues influence coloration.展开更多
基金This study was financially supported by AFOSR/EOARD (grant FA8655-08-1-3012).
文摘Male Lawes’s Parotia,a bird of paradise,use the highly directional reflection of the structurally colored,brilliant-silvery occipital feathers in their courtship display.As in other birds,the structural coloration is produced by ordered melanin pigmentation.The barbules of the Parotia’s occipital feathers,with thickness,3 μm,contain 6–7 layers of densely packed melanin rodlets(diameter,0.25 μm,length,2 μm).The effectively,0.2 μm thick melanin layers separated by,0.2 μm thick keratin layers create a multilayer interference reflector.Reflectance measurements yielded peak wavelengths in the near-infrared at,1.3 μm,i.e.,far outside the visible wavelength range.With the Jamin-Lebedeff interference microscopy method recently developed for pigmented media,we here determined the refractive index of the intact barbules.We thus derived the wavelength dependence of the refractive index of the barbules’melanin to be 1.7–1.8 in the visible wavelength range.Implementing the anatomical and refractive index data in an optical multilayer model,we calculated the barbules’reflectance,transmittance and absorptance spectra,thereby confirming measured spectra.
基金This study was financially supported by the Air Force Office of Scientific Research/European Office of Aerospace Research and Development AFOSR/EOARD(grant FA8655-08-1-3012).
文摘Jamin–Lebedeff polarizing interference microscopy is a classical method for determining the refractive index and thickness of transparent tissues.Here,we extend the application of this method to pigmented,absorbing biological tissues,based on a theoretical derivation using Jones calculus.This novel method is applied to the wings of the American Rubyspot damselfly,Hetaerina americana.The membranes in the red-colored parts of the damselfly’s wings,with a thickness of 2.5 μm,contain a pigment with maximal absorption at 490 nm and a peak absorbance coefficient of 0.7 μm^(-1).The high pigment density causes a considerable and anomalous dispersion of the refractive index.This result can be quantitatively understood from the pigment absorbance spectrum by applying the Kramers–Kronig dispersion relations.Measurements of the spectral dependence of the refractive index and the absorption are valuable for gaining quantitative insight into how the material properties of animal tissues influence coloration.
