AsianScientist (Apr. 23, 2018) – In a study published in Science Advances, researchers have used microscopy to reveal the metallic hues of a 200-million-year-old insect.
The brightly colored wings of insects such as butterflies and moths (Lepidoptera) are the product of structural color, where color is produced by the selective scattering of light rather than pigmentation. In recent years, there has been intense research interest in the structure and photonic properties of lepidopteran wing scales; however, the deep evolutionary history of structural colors is poorly understood.
In the present study, researchers from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences and their colleagues from Germany and the UK describe the scale architectures of Lepidoptera from the Jurassic and a related group (Tarachoptera) fossilised in mid-Cretaceous Burmese amber.
The Jurassic lepidopterans exhibit a type 1 bilayer scale vestiture, namely an upper layer of large fused cover scales and a lower layer of small fused ground scales. This scale arrangement, plus preserved herringbone ornamentation on the cover scale surface, is almost identical to those of some extant Micropterigidae.
Critically, the fossil scales had a repetitive pattern, with a periodicity of 140-2,000 nm, and were therefore capable of scattering visible light. Optical modeling confirmed the fossil cover scales could scatter light in such a way that the wings would have appeared metallic.
In contrast, the fossil tarachopteran scales were smaller and did not have a regular arrangement. Combined, these new results provide the earliest evidence for structural coloration in fossil lepidopterans and support the hypothesis that fused wing scales and the type 1 bilayer covering are fundamental features of the group.
The team next plans to characterize the optical response of scale nanostructures in other fossil specimens. Such evidence for the presence of scale pigments in fossil lepidopterans will inform models of the evolution of structural colors in lepidopterans, the researchers said.
The article can be found at: Zhang et al. (2018) Fossil Scales Illuminate the Early Evolution of Lepidopterans and Structural Colors.
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Source: Chinese Academy of Sciences; Photo: Yang Dinghua.
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