Fossil scales illuminate the early evolution of lepidopterans and structural colors
Qingqing Zhang1,2, Wolfram Mey3, Jörg Ansorge4, Timothy A. Starkey5, Luke T. McDonald6, Maria E. McNamara6, Edmund A. Jarzembowski1,7, Wilfried Wichard8, Richard Kelly9,10, Xiaoyin Ren1, Jun Chen1,11, Haichun Zhang1 and Bo Wang1,12,*
1State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China.
2University of Sciences and Technology of China, Hefei 230026, China.
3Museum für Naturkunde, Leibniz Institute of Evolution and Biodiversity Research, Humboldt University, D-10115 Berlin, Germany.
4Institute of Geography and Geology, University of Greifswald, D-17487 Greifswald, Germany.
5Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, UK.
6School of Biological, Earth and Environmental Sciences, University College Cork, North Mall, Cork T23 TK30, Ireland.
7Department of Earth Sciences, Natural History Museum, London SW7 5BD, UK.
8Institute of Biology and its Didactics, University of Cologne, D-50931 Cologne, Germany.
9School of Earth Sciences, University of Bristol, Bristol BS8 1TQ, UK.
10Department of Natural Sciences, National Museum of Scotland, Edinburgh EH1 1JF, UK.
11Institute of Geology and Paleontology, Linyi University, Linyi 276000, China.
12Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
↵*Corresponding author. Email: bowang@nigpas.ac.cn
Science Advances 11 Apr 2018: Vol. 4, no. 4, e1700988
Source/Fonte: Zhang Qingqing et al.
Abstract
Lepidopteran scales exhibit remarkably complex ultrastructures, many of which produce structural colors that are the basis for diverse communication strategies. Little is known, however, about the early evolution of lepidopteran scales and their photonic structures. We report scale architectures from Jurassic Lepidoptera from the United Kingdom, Germany, Kazakhstan, and China and from Tarachoptera (a stem group of Amphiesmenoptera) from mid-Cretaceous Burmese amber. The Jurassic lepidopterans exhibit a type 1 bilayer scale vestiture: 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 scale ultrastructures have periodicities measuring from 140 to 2000 nm and are therefore capable of scattering visible light, providing the earliest evidence of structural colors in the insect fossil record. Optical modeling confirms that diffraction-related scattering mechanisms dominate the photonic properties of the fossil cover scales, which would have displayed broadband metallic hues as in numerous extant Micropterigidae. The fossil tarachopteran scales exhibit a unique suite of characteristics, including small size, elongate-spatulate shape, ridged ornamentation, and irregular arrangement, providing novel insight into the early evolution of lepidopteran scales. Combined, our 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 groundplan features of the group. Wing scales likely had deep origins in earlier amphiesmenopteran lineages before the appearance of the Lepidoptera.
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