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Spectral tuning of the scale reflectance. (a) Absorbance spectra of single wing scales immersed in a refractive index liquid. The wing scales contain different compositions of two different absorbing pigments (see also table 1). (b) Reflectance spectra of the wings measured with an integrating sphere. Most birdwings are green, with maximal reflectance at approximately 550 nm, but the blue-coloured O. urvillianus has a reflectance peaking at approximately 490 nm and the orange O. croesus reflects maximally at approximately 660 nm.
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The colourful wing patterns of butterflies play an important role for enhancing fitness; for instance, by providing camouflage, for interspecific mate recognition, or for aposematic display. Closely related butterfly species can have dramatically different wing patterns. The phenomenon is assumed to be caused by ecological processes with changing c...
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... ornithopterans and pigment distribution in the differ- ent coloured wing scales. The saturation of the colour corresponds to the (relative) amount of pigment scaled to the maximum absorbance observed in all investigated scales (see also figure 4a). ...
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... identify the pigments of the scales of the various bird- wing species and to determine their spectral characteristics, we immersed single scales in refractive index matching fluid (n ¼ 1.55) and measured absorbance spectra with a micro- spectrophotometer (MSP, figure 4a). The scales of the studied birdwing butterflies yielded two classes of absorbance spectra. ...
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... scales of O. urvillianus contained a predominantly UV-absorbing pigment, with peak absorbance at approximately 375 nm, whereas the scales of O. tithonus contained a blue- absorbing pigment, absorbing maximally at approximately 460 nm. Some scales, like those of O. croesus contained a mixture of both pigments (figures 1, 4a). ...
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... 12: 20150717 patterns, which however, strongly vary in colour; (ii) the Schoenbergia are monocoloured with strongly coloured yellow-green scales and angular (i.e. asymmetric-sized) wing features that further only contain the blue-absorbing papiliochrome pigment leading to strongly chromatic signals ( figure 4; electronic supplementary material, figure S2); ...
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... Bar graphs of the relative excitation of the set of photoreceptors for the different coloured wing areas of the butterflies of the subgenera Ornithoptera (I), Schoenbergia (II) and Aethoptera (III). The reflectance spectra of figure 4b were convoluted with a CIE D 65 standard illuminant spectrum and each of the photoreceptor spectral sensitivities. The obtained values were subsequently normalized to the highest excitation per species. ...
Citations
... Butterfly wing colors are predominantly due to pigmented scales (Umebachi, 1985;Nijhout, 1997;Wijnen et al., 2007;Reed et al., 2008;Zhang et al., 2017;Matsuoka and Monteiro, 2018), structurally colored scales (Lloyd and Nadeau, 2021;Thayer and Patel, 2023), or seldom from pigmented or nanostructured wing membranes (Yoshioka and Kinoshita, 2006;Finet et al., 2023;Nishida et al., 2023;Stavenga, 2023). In the last decade, studies have shown that coloration often results from a combination of both pigments and nanostructures present in the same scale (Wilts et al., 2012a(Wilts et al., , 2012b(Wilts et al., , 2015Wasik et al., 2014;Stavenga et al., 2015;Thayer et al., 2020;Prakash et al., 2022b), and have identified genes, such as cortex, yellow, DOPA decarboxylase, Antennapedia, and Optix, that regulate both traits (Zhang et al., 2017;Matsuoka and Monteiro, 2018;Livraghi et al., 2021;Prakash et al., 2022b). ...
Previous studies have shown that Optix regulates lower lamina thickness and the type of pigment that is produced in wing scales of a few butterfly species. However, the role of Optix in regulating pigment production across species, and in regulating additional aspects of scale morphology remains to be investigated. By combining microspectrophotometry, scanning electron microscopy, and focused ion beam technology on wild-type and Optix Bicyclus anynana crispants, we show that Optix regulates the production of orange pigments (ommochromes), represses the production of brown pigments (melanins), and regulates the morphology of the lower and upper surface of orange scales. Our findings suggest a conserved role of Optix as a switch gene that activates ommochrome and represses melanin synthesis across butterflies. By comparing these effects with other mutations, where only melanin is removed from scales, we propose that pigmentary changes, alone, affect the way that chitin polymerizes within a scale, changing lower lamina thickness as well as multiple intricate structures of the upper surface.
... The brightest colours in nature are often obtained by the interaction of light with ordered nanostructured materials (often referred to as photonic crystals) through interference [1,2]. These structures are widespread in terrestrial [3,4] and marine animals [5] and their role is well understood in insects in terms of communication, mate attraction and predation, impacting the individual's chances of reproducing and surviving [6,7]. However, structural colours are also present in photosynthetic organisms including red, green and brown macroalgae [8], diatoms [9], and land plants [10]. ...
Marine life is populated by a huge diversity of organisms with an incredible range of colour. While structural colour mechanisms and functions are usually well studied in marine animal species, there is a huge knowledge gap regarding the marine macroalgae (red, green and brown seaweeds) that have structural coloration and the biological significance of this phenomenon in these photosynthetic organisms. Here we show that structural colour in the gametophyte life history phase of the red alga Chondrus crispus plays an important role as a photoprotective mechanism in synergy with the other pigments present. In particular, we have demonstrated that blue structural coloration attenuates the more energetic light while simultaneously favouring green and red light harvesting through the external antennae (phycobilisomes) which possess an intensity-dependent photoprotection mechanism. These insights into the relationship between structural colour and photosynthetic light management further our understanding of the mechanisms involved.
... Stavenga et al. 2014a, b, Stavenga 2023. For instance, some butterflies exhibit aposematic colour patterns or tuned colours for mate recognition and signalling on their wings, derived from wing scales coupled with pigments and/or nanostructures (Wilts et al. 2015(Wilts et al. , 2017. Hence, a colour mixing strategy exists in butterfly wings, probably harbouring multiple functions and multiple visual receivers (Vukusic et al 2000, Vukusic 2006. ...
Colour lightness has received considerable attention owing to its diverse functional aspects, such as in thermoregulation, pathogen resistance, and photoprotection. However, the theoretical basis underlying the function of colour lightness is closely related to melanin pigments. Therefore, here we discuss that neglecting other colour-producing mechanisms may bias interpretation of the results. In general, colour lightness is indiscriminately employed as a measure of melanization. Nevertheless, animals may exhibit colours that derive from several pigmentary and structural mechanisms other than melanin. Our primary argument is that colour lightness should not be used indiscriminately before knowing the colour-producing mechanism and validating correlated physiological parameters. For instance, the use of colour lightness as a proxy for thermal or photoprotection function must be validated for pterins, ommochromes, and structural colours.
... Butterflies are known to use a combination of pigmentary and structural coloration to achieve a wide range of colors [16][17][18][19][20][21][22][23]. Butterflies living in remote and endangered places are still being investigated to determine the origin and the role of their coloration. ...
Nature produces some of the most striking optical effects through the combination of structural and chemical principles to give rise to a wide range of colors. However, creating non-spectral colors that extend beyond the color spectrum is a challenging task, as it requires meeting the requirements of both structural and pigmentary coloration. In this study, we investigate the magenta non-spectral color found in the scales of the ventral spots of the Lyropteryx apollonia butterfly. By employing correlated optical and electron microscopy, as well as pigment extraction techniques, we reveal how this color arises from the co-modulation of pigmentary and structural coloration. Specifically, the angle-dependent blue coloration results from the interference of visible light with chitin-based nanostructures, while the diffused red coloration is generated by an ommochrome pigment. The ability to produce such highly conspicuous non-spectral colors provides insights for the development of hierarchical structures with precise control over their optical response. These structures can be used to create hierarchically-arranged systems with a broadened color palette.
... There may be chemical pigments (e.g. melanin, ommochromes, papiliochromes; see Glossary) in any part of the scale (Stavenga et al., 2014a;Wilts et al., 2015). Because chitin has a sufficiently high refractive index (∼1.5; ...
... (see Dataset 1 in Dryad, https://doi.org/10.5061/dryad.qnk98sfnx). Nearly all of these structures were documented by at least one micrograph, except where species in larger studies were simply described as having the same scale anatomy as a relative for which data were shown (Wilts et al., 2015;Giraldo et al., 2016). All but 10 structures belonged to the same category as one of the examples presented in Fig. 1, while allowing for variation in the number of layers in a multilayer, the angular orientation of the layers and the filling fraction of photonic crystals. ...
... The best example -Ornithoptera croesus lydiushad lumen multilayers with reflectance varying among individuals from orange to red (Zhang et al., 2014;Kazama et al., 2017). However, reflectance in O. croesus scales also requires a filtering pigment that absorbs blue light (Wilts et al., 2015). Less compelling examples include two lamina thin films with modest reflectance in both the far red and violet wavelengths that combine to a dim magenta (Thayer et al., 2020). ...
Butterfly scales are among the richest natural sources of optical nanostructures, which produce structural color and iridescence. Several recurring nanostructure types have been described, such as ridge multilayers, gyroids and lower lamina thin films. While the optical mechanisms of these nanostructure classes are known, their phylogenetic distributions and functional ranges have not been described in detail. In this Review, we examine a century of research on the biological production of structural colors, including their evolution, development and genetic regulation. We have also created a database of more than 300 optical nanostructures in butterflies and conducted a meta-analysis of the color range, abundance and phylogenetic distribution of each nanostructure class. Butterfly structural colors are ubiquitous in short wavelengths but extremely rare in long wavelengths, especially red. In particular, blue wavelengths (around 450 nm) occur in more clades and are produced by more kinds of nanostructures than other hues. Nanostructure categories differ in prevalence, phylogenetic distribution, color range and brightness. For example, lamina thin films are the least bright; perforated lumen multilayers occur most often but are almost entirely restricted to the family Lycaenidae; and 3D photonic crystals, including gyroids, have the narrowest wavelength range (from about 450 to 550 nm). We discuss the implications of these patterns in terms of nanostructure evolution, physical constraint and relationships to pigmentary color. Finally, we highlight opportunities for future research, such as analyses of subadult and Hesperid structural colors and the identification of genes that directly build the nanostructures, with relevance for biomimetic engineering.
... [12][13][14] A scale is a complex cuticular structure derived from a single scale cell; scale color can be produced by pigment deposition, 15 by micro-/nanoscopic structures that produce color through optical interference and grating diffraction, [16][17][18] or by a combination of both (pigment and structural color). [19][20][21] In general, wing coloration is a product of various factors, including scale pigment types, scale shape and size, scale nanostructures, scale arrangement, and their position. [22][23][24] Living scale cells do not contribute to the wing color pattern in mature butterflies because they usually disappear at the moment of adult eclosion. ...
A previously undescribed mechanism underlying butterfly wing coloration patterns was discovered in two distantly related butterfly species, Siproeta stelenes and Philaethria diatonica. These butterflies have bright green wings, but the color pattern is not derived from solid pigments or nanostructures of the scales or from the color of the cuticular membrane but rather from a liquid retained in the wing membrane. Wing structure differs between the green and non-green areas. In the non-green region, the upper and lower cuticular membranes are attached to each other, whereas in the green region, we observed a space of 5–10 μm where green liquid is held and living cells are present. A pigment analysis and tracer experiment revealed that the color of the liquid is derived from hemolymph components, bilin and carotenoid pigments. This discovery broadens our understanding of the diverse ways in which butterfly wings obtain their coloration and patterns.
... We can cite the unrivalled metallic shades of the blue morpho, the sumptuous iridescent train of the male peacock, the warning blue rings of the deadliest octopuses, or even the brilliance of the blue coral-reef damselfish. Green colours often result from the interaction between pigments and nanostructures (Shawkey and D'Alba, 2017), which can lead to extreme glistening iridescent green hues in insects (Vukusic et al., 2000;Seago et al., 2009;Wilts et al., 2012aWilts et al., , 2015 and in birds (Durrer, 1986;D'Alba et al., 2012). But the range of structural colours does not stop there: extravagant reddish pink in birds (Durrer, 1986), metallic silver across the animal kingdom (McKenzie et al., 1995;Holt et al., 2011;Neville, 1977;Ren et al., 2020), metallic gold in insects (Neville, 1977;Kilchoer et al., 2019), and mother-of-pearl in nacreous molluscs and butterflies (Jackson et al., 2010;Stavenga, 2021) are a few examples of the richness of the colour palette. ...
Structural coloration is the production of colour by micro- or nano-structures fine enough to interfere with visible light. Structural colouration is responsible for the blues and greens of many animals, as well as for the gold, silver, and some purple-pink colours. These are often saturated and might be extremely shimmering and/or iridescent. The study of structural coloration is an active and interdisciplinary field of research where biology, physics and engineering meet. However, the fascination of humans for stunning structural colours is broader than the framework of science. Here, I provide a series of examples of the use of natural structurally coloured materials in art across the ages and places. I argue that the view from ethnozoology is necessary to gain a comprehensive understanding and appreciation of structural coloration.
... Lepidopteran scales exhibit exquisite architectures for multiple survival strategies, such as heat management, courtship, and camouflage [25][26][27][28] . Morpho theseus juturna, a Neotropical butterfly mainly living in Central America, is particularly noticeable owing to the dense bright white scales covering almost all the ventral region. ...
As one of the most fascinating phenomena, structural whiteness in natural organisms serves important functions in thermoregulation and mating. However, the architectures that cause visible broadband reflection are often in quasiordered distributions, which hinders systematic research on their color formation mechanisms. Here, through numerical analysis, the architectures in Morpho theseus scales are shown to be distributed in various tubular morphologies between tubular and gyroid structures. Then, the mechanism of structural white is discussed using the numerical model built with the combination of a periodic numerical framework and random elements. Thermodynamic experiments indicate that the white scales can efficiently help reduce the temperature of butterfly wings under a direct light beam. Our work provides a concise method for analyzing quasiordered structures. The methodology developed by this numerical model can facilitate a deep understanding of the performance improvement facilitated by these structural characteristics. Corresponding solutions can guide the design of nano-optical materials to achieve an efficient cooling, camouflage, and photothermal conversion system.
... Constructive interference, diffraction and scattering of light are the main physical phenomena that produce structural colours [8,9]. Structural colours are common in nature, found in organisms ranging from birds [5,7,[10][11][12][13][14][15][16][17][18][19] and insects [20][21][22][23] to land plants [24,25] and even algae [26]. ...
The bright, saturated iridescent colours of feathers are commonly produced by single and multi-layers of nanostructured melanin granules (melanosomes), air and keratin matrices, surrounded by an outer keratin cortex of varying thicknesses. The role of the keratin cortex in colour production remains unclear, despite its potential to act as a thin film or absorbing layer. We use electron microscopy, optical simulations and oxygen plasma-mediated experimental cortex removal to show that differences in keratin cortex thickness play a significant role in producing colours. The results indicate that keratin cortex thickness determines the position of the major reflectance peak (hue) from nanostructured melanosomes of common pheasant (Phasianus colchicus) feathers. Specifically, the common pheasant has appropriate keratin cortex thickness to produce blue and green structural colours. This finding identifies a general principle of structural colour production and sheds light on the processes that shaped the evolution of brilliant iridescent colours in the common pheasant.
... [12][13][14] A scale is a complex cuticular structure derived from a single scale cell; scale color can be produced by pigment deposition, 15 by micro-/nanoscopic structures that produce color through optical interference and grating diffraction, [16][17][18] or by a combination of both (pigment and structural color). [19][20][21] In general, wing coloration is a product of various factors, including scale pigment types, scale shape and size, scale nanostructures, scale arrangement, and their position. [22][23][24] Living scale cells do not contribute to the wing color pattern in mature butterflies because they usually disappear at the moment of adult eclosion. ...
