Structural Colors in the Realm of Nature

Kinoshita, Shūichi

doi:10.1142/6496

Cited by 279 publications

(298 citation statements)

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“…The iridescence of the central spot, however, is somewhat atypical for a layered reflector. As usual, with increasing reflection angle, the hue of the reflected light shifts toward shorter wavelengths (10,19), but instead of increasing, the reflectance amplitude sharply falls off for increasing reflection angles and vanishes for reflection angles ≥60°. Measurement of the angledependent reflectance documents this even more clearly.…”

Section: Angle-and Wavelength-dependence Of the Occipital Feathers'mentioning

confidence: 51%

“…For instance, carotenoids cause the colorful yellow or red feathers of many songbirds (5), and the ubiquitous, broad-band absorbing pigment melanin causes feathers to be black (6). Structural colors occur in feather barbs due to quasiordered spongy structures, and in feather barbules due to melanosomes--nanosized, melanin-containing granules--regularly arranged in layers within a keratin matrix, resulting in directional reflections because of constructive interference (7)(8)(9)(10)(11). Differences in the morphology of the structural colored feathers, i.e., in the dimensions of the spongy structured barbs or the melanosome multilayers in the barbules, can modify the color of the reflected light and can thus tune the optical properties of the feathers.…”

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confidence: 99%

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Sparkling feather reflections of a bird-of-paradise explained by finite-difference time-domain modeling

Wilts

Michielsen²,

Raedt

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

109

121

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Birds-of-paradise are nature's prime examples of the evolution of color by sexual selection. Their brilliant, structurally colored feathers play a principal role in mating displays. The structural coloration of both the occipital and breast feathers of the bird-of-paradise Lawes' parotia is produced by melanin rodlets arranged in layers, together acting as interference reflectors. Light reflection by the silvery colored occipital feathers is unidirectional as in a classical multilayer, but the reflection by the richly colored breast feathers is threedirectional and extraordinarily complex. Here we show that the reflection properties of both feather types can be quantitatively explained by finite-difference time-domain modeling using realistic feather anatomies and experimentally determined refractive index dispersion values of keratin and melanin. The results elucidate the interplay between avian coloration and vision and indicate tuning of the mating displays to the spectral properties of the avian visual system. biophotonics | body colors | courtship | signaling | reflectance B irds-of-paradise are best known for their magnificent coloration. Living isolated on Papua New Guinea and its satellite islands (1), the absence of predators has allowed these birds to become extremely specialized for female sexual selection (2). Male birds-of-paradise have evolved extravagant ornamental traits, with intricate sounds and ritualized sets of dance steps and movements accompanied by simultaneous elaborate feather movements, all combined in beautiful displays to win the favor of females (1-4). Among the 39 species of birds-of-paradise almost all colors of the rainbow can be found, and often the males advertise themselves with brilliant, vivid colors framed within a jet-black background. The females on the other hand have dull brownish plumage which has remained in its ancestral color state (1, 2).Whereas the biological purpose of the colorful displays is relatively well understood (1, 2), the coloration mechanisms of the birds' displays and the connection to the visual system of the animals are poorly explored. Feather coloration can be generally categorized in two forms: pigmentary and structural. Randomly arranged, inhomogeneous media containing pigments are colored, because the pigments absorb the diffusely scattered light in a restricted wavelength range. For instance, carotenoids cause the colorful yellow or red feathers of many songbirds (5), and the ubiquitous, broad-band absorbing pigment melanin causes feathers to be black (6). Structural colors occur in feather barbs due to quasiordered spongy structures, and in feather barbules due to melanosomes--nanosized, melanin-containing granules--regularly arranged in layers within a keratin matrix, resulting in directional reflections because of constructive interference (7-11). Differences in the morphology of the structural colored feathers, i.e., in the dimensions of the spongy structured barbs or the melanosome multilayers in the barbules, can modify the color of the ...

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Section: Angle-and Wavelength-dependence Of the Occipital Feathers'mentioning

confidence: 51%

mentioning

confidence: 99%

Sparkling feather reflections of a bird-of-paradise explained by finite-difference time-domain modeling

Wilts

Michielsen²,

Raedt

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

109

121

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“…With only minor changes of the viewing angle, the shiny spots feature strikingly different colours, which give them a diamond-like appearance. The strong directionality of the reflections indicates that the origin of these local, vivid colours is structural [2,3]. A closer look at the elytral pits shows that the diamond-like spots are assemblies of highly directionally reflective scales covering the walls of concave pits in the elytra (figure 1b).…”

Section: Results (A) Optical Appearance Of the Diamond Weevil Scalesmentioning

confidence: 99%

“…Structural (or physical) coloration is due to nanometre-sized structures with periodically changing refractive indices, causing coherent light scattering. Pigmentary coloration is by far the most common in the animal kingdom, but structural coloration is widely encountered as well, and not seldom structural colours are modified by spectrally filtering pigments [1,2,9].…”

Section: Introductionmentioning

confidence: 99%

Brilliant camouflage : photonic crystals in the diamond weevil, Entimus imperialis

et al. 2012

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The neotropical diamond weevil, Entimus imperialis, is marked by rows of brilliant spots on the overall black elytra. The spots are concave pits with intricate patterns of structural-coloured scales, consisting of large domains of three-dimensional photonic crystals that have a diamond-type structure. Reflectance spectra measured from individual scale domains perfectly match model spectra, calculated with anatomical data and finite-difference time-domain methods. The reflections of single domains are extremely directional (observed with a point source less than 58), but the special arrangement of the scales in the concave pits significantly broadens the angular distribution of the reflections. The resulting virtually angle-independent green coloration of the weevil closely approximates the colour of a foliaceous background. While the closedistance colourful shininess of E. imperialis may facilitate intersexual recognition, the diffuse green reflectance of the elytra when seen at long-distance provides cryptic camouflage.

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“…On the other hand, the variability or flexibility of the microstructure implies that it is inevitably accompanied by temporal fluctuations [36]. The dynamical measurement of the reflected light intensity may reveal such fluctuation in the variable multilayer system, which is thought to include random motion of a single platelet owing to the Brownian motion of water molecules and also the collective motion of the several platelets within a stack.…”

Section: Discussionmentioning

confidence: 99%

Mechanism of variable structural colour in the neon tetra: quantitative evaluation of the Venetian blind model

Yoshioka

Matsuhana

Tanaka

et al. 2010

J. R. Soc. Interface.

115

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The structural colour of the neon tetra is distinguishable from those of, e.g., butterfly wings and bird feathers, because it can change in response to the light intensity of the surrounding environment. This fact clearly indicates the variability of the colour-producing microstructures. It has been known that an iridophore of the neon tetra contains a few stacks of periodically arranged light-reflecting platelets, which can cause multilayer optical interference phenomena. As a mechanism of the colour variability, the Venetian blind model has been proposed, in which the light-reflecting platelets are assumed to be tilted during colour change, resulting in a variation in the spacing between the platelets. In order to quantitatively evaluate the validity of this model, we have performed a detailed optical study of a single stack of platelets inside an iridophore. In particular, we have prepared a new optical system that can simultaneously measure both the spectrum and direction of the reflected light, which are expected to be closely related to each other in the Venetian blind model. The experimental results and detailed analysis are found to quantitatively verify the model.

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Structural Colors in the Realm of Nature

Cited by 279 publications

References 0 publications

Sparkling feather reflections of a bird-of-paradise explained by finite-difference time-domain modeling

Sparkling feather reflections of a bird-of-paradise explained by finite-difference time-domain modeling

Brilliant camouflage : photonic crystals in the diamond weevil, Entimus imperialis

Mechanism of variable structural colour in the neon tetra: quantitative evaluation of the Venetian blind model

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