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Singla S, Yang Z, Patil A, Guo H, Vanthournout B, Htut KZ, Shawkey MD, Tsige M, Dhinojwala A. Influence of Core Type and Shell Thickness on Avian-Inspired Structural Colors Produced from Melanin Nanoparticle Assemblies. ACS APPLIED MATERIALS & INTERFACES 2023; 15:45229-45238. [PMID: 37699412 DOI: 10.1021/acsami.3c08152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/14/2023]
Abstract
Hollow melanosomes found in iridescent bird feathers, including violet-backed starlings and wild turkeys, enable the generation of diverse structural colors. It has been postulated that the high refractive index (RI) contrast between melanin (1.74) and air (1.0) results in brighter and more saturated colors. This has led to several studies that have synthesized hollow synthetic melanin nanoparticles and fabricated colloidal nanostructures to produce synthetic structural colors. However, these studies use hollow nanoparticles with thin shells (<20 nm), even though shell thicknesses as high as 100 nm have been observed in natural melanosomes. Here, we combine experimental and computational approaches to examine the influence of the varying polydopamine (PDA, synthetic melanin) shell thickness (0-100 nm) and core material on structural colors. Experimentally, a concomitant change in overall particle size and RI contrast makes it difficult to interpret the effect of a hollow or solid core on color. Thus, we utilize finite-difference time-domain (FDTD) simulations to uncover the effect of shell thickness and core on structural colors. Our FDTD results highlight that hollow particles with thin shells have substantially higher saturation than same-sized solid and core-shell particles. These results would benefit a wide range of applications including paints, coatings, and cosmetics.
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Affiliation(s)
- Saranshu Singla
- School of Polymer Science and Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Zepeng Yang
- School of Polymer Science and Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Anvay Patil
- School of Polymer Science and Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Hao Guo
- School of Polymer Science and Engineering, The University of Akron, Akron, Ohio 44325, United States
| | | | - K Zin Htut
- School of Polymer Science and Engineering, The University of Akron, Akron, Ohio 44325, United States
| | | | - Mesfin Tsige
- School of Polymer Science and Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Ali Dhinojwala
- School of Polymer Science and Engineering, The University of Akron, Akron, Ohio 44325, United States
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2
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Jeon DJ, Ji S, Lee E, Kang J, Kim J, D'Alba L, Manceau M, Shawkey MD, Yeo JS. How keratin cortex thickness affects iridescent feather colours. ROYAL SOCIETY OPEN SCIENCE 2023; 10:220786. [PMID: 36686555 PMCID: PMC9832292 DOI: 10.1098/rsos.220786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 12/06/2022] [Indexed: 06/17/2023]
Abstract
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.
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Affiliation(s)
- Deok-Jin Jeon
- School of Integrated Technology, Yonsei Institute of Convergence Technology, Yonsei University, Incheon 21983, Republic of Korea
| | - Seungmuk Ji
- School of Integrated Technology, Yonsei Institute of Convergence Technology, Yonsei University, Incheon 21983, Republic of Korea
| | - Eunok Lee
- Department of Research Planning, National Institute of Ecology, Chungcheongnam-do 33657, Republic of Korea
| | - Jihun Kang
- School of Integrated Technology, Yonsei Institute of Convergence Technology, Yonsei University, Incheon 21983, Republic of Korea
| | - Jiyeong Kim
- Ecological Technology Research Team, Division of Ecological Applications Research, National Institute of Ecology, Chungcheongnam-do 33657, Republic of Korea
| | - Liliana D'Alba
- Evolution and Optics of Nanostructures Group, Department of Biology, Ghent University, Ledeganckstraat 35, Ghent 9000, Belgium
- Naturalis Biodiversity Center, Darwinweg 2, Leiden 2333 CR, The Netherlands
| | - Marie Manceau
- Center for Interdisciplinary Research in Biology, CNRS UMR7241, INSERM U1050, Collège de France, Paris Sciences et Lettres University, 75006 Paris, France
| | - Matthew D. Shawkey
- Evolution and Optics of Nanostructures Group, Department of Biology, Ghent University, Ledeganckstraat 35, Ghent 9000, Belgium
| | - Jong-Souk Yeo
- School of Integrated Technology, Yonsei Institute of Convergence Technology, Yonsei University, Incheon 21983, Republic of Korea
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Nordén KK, Eliason CM, Stoddard MC. Evolution of brilliant iridescent feather nanostructures. eLife 2021; 10:e71179. [PMID: 34930526 PMCID: PMC8691833 DOI: 10.7554/elife.71179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 11/19/2021] [Indexed: 12/19/2022] Open
Abstract
The brilliant iridescent plumage of birds creates some of the most stunning color displays known in the natural world. Iridescent plumage colors are produced by nanostructures in feathers and have evolved in diverse birds. The building blocks of these structures-melanosomes (melanin-filled organelles)-come in a variety of forms, yet how these different forms contribute to color production across birds remains unclear. Here, we leverage evolutionary analyses, optical simulations, and reflectance spectrophotometry to uncover general principles that govern the production of brilliant iridescence. We find that a key feature that unites all melanosome forms in brilliant iridescent structures is thin melanin layers. Birds have achieved this in multiple ways: by decreasing the size of the melanosome directly, by hollowing out the interior, or by flattening the melanosome into a platelet. The evolution of thin melanin layers unlocks color-producing possibilities, more than doubling the range of colors that can be produced with a thick melanin layer and simultaneously increasing brightness. We discuss the implications of these findings for the evolution of iridescent structures in birds and propose two evolutionary paths to brilliant iridescence.
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Affiliation(s)
- Klara Katarina Nordén
- Department of Ecology and Evolutionary Biology, Princeton UniversityPrincetonUnited States
| | - Chad M Eliason
- Grainger Bioinformatics Center, Field Museum of Natural HistoryChicagoUnited States
| | - Mary Caswell Stoddard
- Department of Ecology and Evolutionary Biology, Princeton UniversityPrincetonUnited States
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Freyer P, Wilts BD, Stavenga DG. Cortex Thickness Is Key for the Colors of Iridescent Starling Feather Barbules With a Single, Organized Melanosome Layer. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.746254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The iridescent plumage of many birds is structurally colored due to an orderly arrangement of melanosomes in their feather barbules. Here, we investigated the blue- to purple-colored feathers of the European starling (Sturnus vulgaris) and the blue and green feathers of the Cape starling (Lamprotornis nitens). In both cases, the barbules contain essentially a single layer of melanosomes, but in S. vulgaris they are solid and rod-shaped, and in L. nitens they are hollow and rod- as well as platelet-shaped. We analyzed the coloration of the feathers by applying imaging scatterometry, bifurcated-probe- and micro-spectrophotometry. The reflectance spectra of the feathers of the European starling showed multiple peaks and a distinct, single peak for the Cape starling feathers. Assuming that the barbules of the two starling species contain a simple multilayer, consisting locally only of a cortex plus a single layer of melanosomes, we interpret the experimental data by applying effective-medium-multilayer modeling. The optical modeling provides quantitative insight into the function of the keratin cortex thickness, being the principal factor to determine the peak wavelength of the reflectance bands; the melanosome layer only plays a minor role. The air cavity in the hollow melanosomes of the Cape starling creates a strongly enhanced refractive index contrast, thus very effectively causing a high reflectance.
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McCoy DE, Shultz AJ, Vidoudez C, van der Heide E, Dall JE, Trauger SA, Haig D. Microstructures amplify carotenoid plumage signals in tanagers. Sci Rep 2021; 11:8582. [PMID: 33883641 PMCID: PMC8060279 DOI: 10.1038/s41598-021-88106-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 04/08/2021] [Indexed: 02/02/2023] Open
Abstract
Brilliantly-colored birds are a model system for research into evolution and sexual selection. Red, orange, and yellow carotenoid-colored plumages have been considered honest signals of condition; however, sex differences in feather pigments and microstructures are not well understood. Here, we show that microstructures, rather than carotenoid pigments, seem to be a major driver of male-female color differences in the social, sexually-dimorphic tanager genus Ramphocelus. We comprehensively quantified feather (i) color (using spectrophotometry), (ii) pigments (using liquid chromatography-mass spectrometry (LC-MS)), and (iii) microstructures (using scanning electron microscopy (SEM) and finite-difference time-domain (FDTD) optical modeling). Males have significantly more saturated color patches than females. However, our exploratory analysis of pigments suggested that males and females have concordant carotenoid pigment profiles across all species (MCMCglmm model, female:male ratio = 0.95). Male, but not female, feathers have elaborate microstructures which amplify color appearance. Oblong, expanded feather barbs in males enhance color saturation (for the same amount of pigment) by increasing the transmission of optical power through the feather. Dihedral barbules (vertically-angled, strap-shaped barbules) in males reduce total reflectance to generate "super black" and "velvet red" plumage. Melanin in females explains some, but not all, of the male-female plumage differences. Our results suggest that a widely cited index of honesty, carotenoid pigments, cannot fully explain male appearance. We propose that males are selected to evolve amplifiers-in this case, microstructures that enhance appearance-that are not necessarily themselves linked to quality.
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Affiliation(s)
- Dakota E McCoy
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
| | - Allison J Shultz
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
- Informatics Group, Harvard University, 38 Oxford Street, Cambridge, MA, 02138, USA
- Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
- Ornithology Department, Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, CA, 90007, USA
| | - Charles Vidoudez
- Harvard Center for Mass Spectrometry, Harvard University, 52 Oxford Street (B2), Cambridge, MA, 02138, USA
| | - Emma van der Heide
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Jacqueline E Dall
- Ornithology Department, Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, CA, 90007, USA
| | - Sunia A Trauger
- Harvard Center for Mass Spectrometry, Harvard University, 52 Oxford Street (B2), Cambridge, MA, 02138, USA
| | - David Haig
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
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Freyer P, Stavenga DG. Biophotonics of diversely coloured peacock tail feathers. Faraday Discuss 2020; 223:49-62. [PMID: 32720960 DOI: 10.1039/d0fd00033g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Peacock feathers feature a rich gamut of colours, created by a most sophisticated structural colouration mechanism. The feather barbules contain biophotonic structures consisting of two-dimensionally-ordered lattices of cylindrical melanosomes and air channels embedded in keratin. Here, we study the reflectance characteristics of the various peacock tail feather colours by applying bifurcated-probe- and micro-spectrophotometry and imaging scatterometry. We compare the experimental results with published anatomical SEM and TEM data, using a transfer-matrix based effective-medium multilayer model that includes the number and diameter of the melanosome rodlets and air channels, the lattice spacing and the keratin cortex thickness, together with the recently determined wavelength-dependence of the refractive indices of keratin and melanin. Slight variations in the parameter values cause substantial changes in the spectral position and shape of the reflectance bands. We find that the number of layers crucially determines the number of peaks in the reflectance spectra. For a small number of melanosome layers, the reflectance band shape is particularly sensitive to the properties of the uppermost layer, which provides a simple mechanism for tuning the feather colours.
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Affiliation(s)
- Pascal Freyer
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands.
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Freyer P, Wilts BD, Stavenga DG. Reflections on iridescent neck and breast feathers of the peacock, Pavo cristatus. Interface Focus 2018; 9:20180043. [PMID: 30603065 DOI: 10.1098/rsfs.2018.0043] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/18/2018] [Indexed: 11/12/2022] Open
Abstract
The blue neck and breast feathers of the peacock are structurally coloured due to an intricate photonic crystal structure in the barbules consisting of a two-dimensionally ordered rectangular lattice of melanosomes (melanin rodlets) and air channels embedded in a keratin matrix. We here investigate the feather coloration by performing microspectrophotometry, imaging scatterometry and angle-dependent reflectance measurements. Using previously determined wavelength-dependent refractive indices of melanin and keratin, we interpret the spectral and spatial reflection characteristics by comparing the measured spectra to calculated spectra by effective-medium multilayer and full three-dimensional finite-difference time-domain modelling. Both modelling methods yield similar reflectance spectra indicating that simple multilayer modelling is adequate for a direct understanding of the brilliant coloration of peacock feathers.
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Affiliation(s)
- Pascal Freyer
- Computational Physics, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Bodo D Wilts
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland
| | - Doekele G Stavenga
- Computational Physics, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
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Gruson H, Andraud C, Daney de Marcillac W, Berthier S, Elias M, Gomez D. Quantitative characterization of iridescent colours in biological studies: a novel method using optical theory. Interface Focus 2018; 9:20180049. [PMID: 30603069 DOI: 10.1098/rsfs.2018.0049] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/11/2018] [Indexed: 11/12/2022] Open
Abstract
Iridescent colours are colours that change with viewing or illumination geometry. While they are widespread in many living organisms, most evolutionary studies on iridescence do not take into account their full complexity. Few studies try to precisely characterize what makes iridescent colours special: their angular dependency. Yet, it is likely that this angular dependency has biological functions and is therefore submitted to evolutionary pressures. For this reason, evolutionary biologists need a repeatable method to measure iridescent colours as well as variables to precisely quantify the angular dependency. In this study, we use a theoretical approach to propose five variables that allow one to fully describe iridescent colours at every angle combination. Based on the results, we propose a new measurement protocol and statistical method to reliably characterize iridescence while minimizing the required number of time-consuming measurements. We use hummingbird iridescent feathers and butterfly iridescent wings as test cases to demonstrate the strengths of this new method. We show that our method is precise enough to be potentially used at intraspecific level while being also time-efficient enough to encompass large taxonomic scales.
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Affiliation(s)
- Hugo Gruson
- CEFE, Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France
| | - Christine Andraud
- CRC, MNHN, Ministère de la Culture et de la Communication, CNRS, Paris, France
| | | | | | - Marianne Elias
- ISYEB, CNRS, MNHN, EPHE, Sorbonne Université, Paris, France
| | - Doris Gomez
- CEFE, Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France.,INSP, Sorbonne Université, CNRS, Paris, France
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Nordén KK, Faber JW, Babarović F, Stubbs TL, Selly T, Schiffbauer JD, Peharec Štefanić P, Mayr G, Smithwick FM, Vinther J. Melanosome diversity and convergence in the evolution of iridescent avian feathers-Implications for paleocolor reconstruction. Evolution 2018; 73:15-27. [PMID: 30411346 PMCID: PMC6587736 DOI: 10.1111/evo.13641] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 10/22/2018] [Indexed: 12/15/2022]
Abstract
Some of the most varied colors in the natural world are created by iridescent nanostructures in bird feathers, formed by layers of melanin‐containing melanosomes. The morphology of melanosomes in iridescent feathers is known to vary, but the extent of this diversity, and when it evolved, is unknown. We use scanning electron microscopy to quantify the diversity of melanosome morphology in iridescent feathers from 97 extant bird species, covering 11 orders. In addition, we assess melanosome morphology in two Eocene birds, which are the stem lineages of groups that respectively exhibit hollow and flat melanosomes today. We find that iridescent feathers contain the most varied melanosome morphologies of all types of bird coloration sampled to date. Using our extended dataset, we predict iridescence in an early Eocene trogon (cf. Primotrogon) but not in the early Eocene swift Scaniacypselus, and neither exhibit the derived melanosome morphologies seen in their modern relatives. Our findings confirm that iridescence is a labile trait that has evolved convergently in several lineages extending down to paravian theropods. The dataset provides a framework to detect iridescence with more confidence in fossil taxa based on melanosome morphology.
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Affiliation(s)
- Klara K Nordén
- School of Earth Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK.,Current address: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08544, USA
| | - Jaeike W Faber
- School of Earth Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK.,Current address: Department of Medical Biology, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands
| | - Frane Babarović
- Current address: Department of Animal and Plant Sciences, University of Sheffield, S10 2TN, Sheffield, UK.,Department of Biology, Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10 000, Zagreb, Croatia
| | - Thomas L Stubbs
- School of Earth Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
| | - Tara Selly
- X-ray Microanalysis Core Facility, University of Missouri, 101 Geological Sciences Building, Columbia, MO, 65211, USA.,Department of Geological Sciences, University of Missouri, 101 Geological Sciences Building, Columbia, MO, 65211, USA
| | - James D Schiffbauer
- X-ray Microanalysis Core Facility, University of Missouri, 101 Geological Sciences Building, Columbia, MO, 65211, USA.,Department of Geological Sciences, University of Missouri, 101 Geological Sciences Building, Columbia, MO, 65211, USA
| | - Petra Peharec Štefanić
- Department of Biology, Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10 000, Zagreb, Croatia
| | - Gerald Mayr
- Senckenberg Research Institute Frankfurt, Senckenberganlage 25, 60325, Frankfurt, Germany
| | - Fiann M Smithwick
- School of Earth Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
| | - Jakob Vinther
- School of Earth Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK.,School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
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