Development of structural colour in leaf beetles

Abstract

Structural colours in living organisms have been observed and analysed in a large number of species, however the study of how the micro- and nano-scopic natural structures responsible of such colourations develop has been largely ignored. Understanding the interplay between chemical composition, structural morphology on multiple length scales, and mechanical constraints requires a range of investigation tools able to capture the different aspects of natural hierarchical architectures. Here, we report a developmental study of the most widespread strategy for structural colouration in nature: the cuticular multilayer. In particular, we focus on the exoskeletal growth of the dock leaf beetle Gastrophysa viridula, capturing all aspects of its formation: the macroscopic growth is tracked via synchrotron microtomography, while the submicron features are revealed by electron microscopy and light spectroscopy combined with numerical modelling. In particular, we observe that the two main factors driving the formation of the colour-producing multilayers are the polymerization of melanin during the ecdysis and the change in the layer spacing during the sclerotisation of the cuticle. Our understanding of the exoskeleton formation provides a unique insight into the different processes involved during metamorphosis.

Genetic manipulation of structural color in bacterial colonies

“…In many species, the biological significance of structural coloration represents an evolutionary advantage for camouflage (10), sexual selection (11), thermal regulation (12), photosynthesis (13,14), and intraspecies signaling (15,16). Despite such a variety of mechanisms and species displaying structural coloration, there is still little knowledge on the processes regulating the development of such colors in any living system (17)(18)(19)(20) in terms of genotype-phenotype relation, which is key to the understanding of development, function, and evolution of structural colors (21).…”

Assembly of cellulose nanocrystals in a levitating drop probed by time-resolved small angle X-ray scattering

“…9 The helical orientation of nanocellulose in plant cell walls has been shown to contribute to both the mechanical strength of wood, [10][11][12] as well as the brilliant colour of different organisms. [13][14][15] Rod-like cellulose nanocrystals (CNC) with a high aspect ratio produced by e.g., sulphuric acid hydrolysis are colloidally stable in aqueous dispersions and form a chiral nematic (cholesteric) liquid crystalline phase at relatively low concentrations. 10,16 Drying of CNC dispersions results in films with a helically arranged structure and iridescent optical appearance with potential applications as sensors and coatings.…”

Structural colors and physical properties of elytra in the jewel beetle, Chrysochroa fulgidissima, using surface analytical techniques

“…The film interference, diffraction grating, scattering, and photonic crystals are the major mechanisms for structural colors 1–3 . The colors of many beetles are produced from film interference, which involves multilayer reflectors, for example, tiger beetles ( Cicindelinae ), the iridescent chrysomelid beetle ( Plateumaris sericea ), and leaf beetles ( Gastrophysa viridula ) 4–7 . Multilayer reflectors of beetles existed at different positions in the integument such as the epicuticlar, exocuticlar, and endocuticlar reflectors 3 …”