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Vanthournout B, Rousaki A, Parmentier T, Janssens F, Mertens J, Vandenabeele P, D'Alba L, Shawkey M. Springtail coloration at a finer scale: mechanisms behind vibrant collembolan metallic colours. J R Soc Interface 2021; 18:20210188. [PMID: 34229459 DOI: 10.1098/rsif.2021.0188] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The mechanisms and evolution of metallic structural colours are of both fundamental and applied interest, yet most work in arthropods has focused on derived butterflies and beetles with distinct hues. In particular, basal hexapods-groups with many scaled, metallic representatives-are currently poorly studied and controversial, with some recent studies suggesting either that thin-film (lamina thickness) or diffraction grating (longitudinal ridges, cross-ribs) elements produce these colours in early Lepidoptera and one springtail (Collembola) species. Especially the collembolan basal scale design, consisting of a single lamina and longitudinal ridges with smooth valleys lacking cross-ribs, makes them an interesting group to explore the mechanisms of metallic coloration. Using microspectroscopy, Raman spectroscopy, electron microscopy and finite-difference time-domain optical modelling, we investigated scale colour in seven springtail species that show clear metallic coloration. Reflectance spectra are largely uniform and exhibit a broadband metallic/golden coloration with peaks in the violet/blue region. Our simulations confirm the role of the longitudinal ridges, working in conjunction with thin-film effects to produce a broadband metallic coloration. Broadband coloration occurs through spatial colour mixing, which probably results from nanoscale variation in scale thickness and ridge height and distance. These results provide crucial insights into the colour production mechanisms in a basal scale design and highlight the need for further investigation of scaled, basal arthropods.
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Affiliation(s)
- Bram Vanthournout
- Evolution and Optics of Nanostructures Group, Department of Biology, Ghent University, Ledeganckstraat 35, Ghent 9000, Belgium
| | - Anastasia Rousaki
- Raman Spectroscopy Research Group, Department of Chemistry, Ghent University, Krijgslaan 281, S12, B-9000 Ghent, Belgium
| | - Thomas Parmentier
- Research Unit of Environmental and Evolutionary Biology, Namur Institute of Complex Systems, and Institute of Life, Earth, and the Environment, Namur University, Rue de Bruxelles 61, 5000 Namur, Belgium.,Terrestrial Ecology Unit, Department of Biology, Ghent University, Ledeganckstraat 35, Ghent 9000, Belgium
| | - Frans Janssens
- Department of Biology, Antwerp University, Antwerp B-2020, Belgium
| | - Johan Mertens
- Terrestrial Ecology Unit, Department of Biology, Ghent University, Ledeganckstraat 35, Ghent 9000, Belgium
| | - Peter Vandenabeele
- Raman Spectroscopy Research Group, Department of Chemistry, Ghent University, Krijgslaan 281, S12, B-9000 Ghent, Belgium.,Archaeometry Research Group, Department of Archaeology, Ghent University, Sint-Pietersnieuwstraat 35, B-9000 Ghent, Belgium
| | - Liliana D'Alba
- Evolution and Optics of Nanostructures Group, Department of Biology, Ghent University, Ledeganckstraat 35, Ghent 9000, Belgium
| | - Matthew Shawkey
- Evolution and Optics of Nanostructures Group, Department of Biology, Ghent University, Ledeganckstraat 35, Ghent 9000, Belgium
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D'Alba L, Meadows M, Maia R, Jong-Souk Y, Manceau M, Shawkey M. Morphogenesis of iridescent feathers in Anna's hummingbird Calypte anna. Integr Comp Biol 2021; 61:1502-1510. [PMID: 34104966 DOI: 10.1093/icb/icab123] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 06/01/2021] [Accepted: 06/07/2021] [Indexed: 12/15/2022] Open
Abstract
Color is a phenotypic trait of utmost importance, particularly in birds, which are known for their diverse color signals and color-producing mechanisms including pigment-based colors, light scattering from nanostructured feather tissues and combinations thereof. Bright iridescent plumage colors of hummingbirds are caused by light scattering by an organized array of flattened, pigment organelles, containing air-filled vesicles, called melanosomes. These hollow platelets are organized in multilayer arrays that contain numerous sharp air/melanin refractive index interfaces, producing brilliant iridescent colors. Despite their ecological significance and potential for inspiration of new optical materials, how platelets form and spatially arrange in nanostructures in growing feathers remains unknown. Here, we tested the hypothesis that melanosome formation and organization occurs mostly through passive self-assembly processes by assembling a developmental time series of growing hummingbird feathers using optical and electron microscopy. We show that hummingbird platelets contain air bubbles or vesicles upon their formation in pigment-producing cells, melanocytes. When melanosomes are transferred to neighboring keratinocytes (the cells shaping barbule structure) they drastically expand in size; and variation in this enlargement appears to be driven by physical constraints caused by the placement of the melanosomes within the barbule plate and their proximity to other melanosomes. As the barbule elongates and narrows, polymerizing feather corneous beta protein (CβP) orients melanosomes unilaterally, forcing them into a stacked configuration. These results reveal potentially novel forces driving the self-assembly of the nanostructures producing some of the brightest colors in nature.<.
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Affiliation(s)
- Liliana D'Alba
- Evolution and Optics of Nanostructures Group, Department of Biology, University of Ghent, Ledeganckstraat 35, Ghent 9000, Belgium
| | - Melissa Meadows
- Department of Biology, University of Florida, 220 Bartram Hall, Gainesville, FL 32611-8525
| | - Rafael Maia
- Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, NY
| | - Yeo Jong-Souk
- School of Integrated Technology, Yonsei University, Incheon, 21983, Republic of Korea
| | - Marie Manceau
- Center for Interdisciplinary Research in Biology, CNRS 7241, INSERM U1050, Collège de France, Paris, France
| | - Matthew Shawkey
- Evolution and Optics of Nanostructures Group, Department of Biology, University of Ghent, Ledeganckstraat 35, Ghent 9000, Belgium
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Cai C, Tihelka E, Pan Y, Yin Z, Jiang R, Xia F, Huang D. Structural colours in diverse Mesozoic insects. Proc Biol Sci 2020; 287:20200301. [PMID: 32605519 DOI: 10.1098/rspb.2020.0301] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Structural colours, nature's most pure and intense colours, originate when light is scattered via nanoscale modulations of the refractive index. Original colours in fossils illuminate the ecological interactions among extinct organisms and functional evolution of colours. Here, we report multiple examples of vivid metallic colours in diverse insects from mid-Cretaceous amber. Scanning and transmission electron microscopy revealed a smooth outer surface and five alternating electron-dense and electron-lucent layers in the epicuticle of a fossil wasp, suggesting that multilayer reflectors, the most common biophotonic nanostructure in animals and even plants, are responsible for the exceptional preservation of colour in amber fossils. Based on theoretical modelling of the reflectance spectra, a reflective peak of wavelength of 514 nm was calculated, corresponding to the bluish-green colour observed under white light. The green to blue structural colours in fossil wasps, beetles and a fly most likely functioned as camouflage, although other functions such as thermoregulation cannot be ruled out. This discovery not only provides critical evidence of evolution of structural colours in arthropods, but also sheds light on the preservation potential of nanostructures of ancient animals through geological time.
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Affiliation(s)
- Chenyang Cai
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China
| | - Erik Tihelka
- Department of Animal Science, Hartpury College, Hartpury GL19 3BE, UK
| | - Yanhong Pan
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China.,School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, People's Republic of China
| | - Ziwei Yin
- Laboratory of Systematic Entomology, College of Life Sciences, Shanghai Normal University, Shanghai 200234, People's Republic of China
| | - Rixin Jiang
- Laboratory of Systematic Entomology, College of Life Sciences, Shanghai Normal University, Shanghai 200234, People's Republic of China
| | - Fangyuan Xia
- Lingpoge Amber Museum, Shanghai 201108, People's Republic of China
| | - Diying Huang
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China
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