Structure and Chemical Organization in Damselfly Calopteryx haemorrhoidalis Wings: A Spatially Resolved FTIR and XRF Analysis with Synchrotron Radiation

Susan Stuhr,Pere Luque,Axel Rosenhahn,Elena P Ivanova,Yang Yang,Jitraporn Vongsvivut,Mohammad Al Kobaisi,Richard Marchant,Robert N Lamb,Vi Khanh Truong,Vladimir A Baulin,Peter Cloetens,Marco Werner,Mark J Tobin,Sergey Rubanov,Tobias Senkbeil

doi:10.1038/s41598-018-26563-6

Abstract

Insects represent the majority of known animal species and exploit a variety of fascinating nanotechnological concepts. We investigated the wings of the damselfly Calopteryx haemorrhoidalis, whose males have dark pigmented wings and females have slightly pigmented wings. We used scanning electron microscopy (SEM) and nanoscale synchrotron X-ray fluorescence (XRF) microscopy analysis for characterizing the nanostructure and the elemental distribution of the wings, respectively. The spatially resolved distribution of the organic constituents was examined by synchrotron Fourier transform infrared (s-FTIR) microspectroscopy and subsequently analyzed using hierarchical cluster analysis. The chemical distribution across the wing was rather uniform with no evidence of melanin in female wings, but with a high content of melanin in male wings. Our data revealed a fiber-like structure of the hairs and confirmed the presence of voids close to its base connecting the hairs to the damselfly wings. Within these voids, all detected elements were found to be locally depleted. Structure and elemental contents varied between wing membranes, hairs and veins. The elemental distribution across the membrane was rather uniform, with higher Ca, Cu and Zn levels in the male damselfly wing membranes.

Highlights

Insects have evolved their ability to fly at least 400 million years ago and represent half of all living organisms on earth
X-ray fluorescence microscopy based on the new X-ray nanoprobe allowed a unique pathway to characterize elemental distributions across the Calopteryx haemorrhoidalis wings, while functionality distributions were characterized by synchrotron-Fourier transform infrared microspectroscopy (s-FTIR)
The low-vacuum Scanning electron microscopic (SEM) technique used in Supplementary Fig. S2 allowed the imaging of damselfly wings to be performed without the use of gold coating on the samples

Summary

Introduction

Insects have evolved their ability to fly at least 400 million years ago and represent half of all living organisms on earth. The aim of this work was to gain a comprehensive understanding of chemical and elemental compositions in different parts of male and female wings of Calopteryx haemorrhoidalis using s-FTIR and synchrotron X-ray fluorescence (XRF) microscopy techniques. The highly collimated synchrotron light source essentially offered the combination of high brilliance, narrow bandwidth and nearly diffraction-limited focus, which exceptionally allows spatially resolved FTIR chemical mapping measurement and nanoscale elemental XRF investigation of the damselfly wings as reported in this study. X-ray fluorescence microscopy is a multi-elemental analytical technique allowing chemical mapping not limited to the surface[16,17,18,19] It allows the non-invasive analysis of the elemental composition of samples and the high penetration depth of about 800 μm at a photon energy of 17 keV provides bulk sensitive information. X-ray fluorescence microscopy based on the new X-ray nanoprobe allowed a unique pathway to characterize elemental distributions across the Calopteryx haemorrhoidalis wings, while functionality distributions were characterized by s-FTIR

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Conclusion