Experimental degradation of helicoidal photonic nanostructures in scarab beetles (Coleoptera: Scarabaeidae): implications for the identification of circularly polarizing cuticle in the fossil record
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Accepted version
Date
2018-11-14
Authors
Odin, Giliane P.
McNamara, Maria E.
Arwin, Hans
Järrendahl, Kenneth
Journal Title
Journal ISSN
Volume Title
Publisher
The Royal Society
Published Version
Abstract
Scarab beetles (Coleoptera: Scarabaeidae) can exhibit striking colours produced by pigments and/or nanostructures. The latter include helicoidal (Bouligand) structures that can generate circularly polarized light. These have a cryptic evolutionary history in part because fossil examples are unknown. This suggests either a real biological signal, i.e. that Bouligand structures did not evolve until recently, or a taphonomic signal, i.e. that conditions during the fossilization process were not conducive to their preservation. We address this issue by experimentally degrading circularly polarizing cuticle of modern scarab beetles to test the relative roles of decay, maturation and taxonomy in controlling preservation. The results reveal that Bouligand structures have the potential to survive fossilization, but preservation is controlled by taxonomy and the diagenetic history of specimens. Further, cuticle of specific genus (Chrysina) is particularly decay-prone in alkaline conditions; this may relate to the presence of certain compounds, e.g. uric acid, in the cuticle of these taxa.
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Keywords
Structural colours , Bouligand structure , Taphonomy , Fossil insects, , Mueller-matrix ellipsometry , Polarization vision , Optical activity , Light , Decay , Preservation , Reflectors , Taphonomy , Origin , Green
Citation
Odin, G. P., McNamara, M. E., Arwin, H. and Järrendahl, K. (2018) 'Experimental degradation of helicoidal photonic nanostructures in scarab beetles (Coleoptera: Scarabaeidae): implications for the identification of circularly polarizing cuticle in the fossil record', Journal of The Royal Society Interface, 15(148), 20180560 (11 pp). doi: 10.1098/rsif.2018.0560