Illuminating the development of structural colour in vivo: Hyperspectral microscopy of butterflies

Session

Poster Session Three

Authors

Professor Peta Clode (5), Dr Anna-Lee Jessop (1), Dr Primoz Pirih (4), Dr Kyle DeMarr (2), Professor Nipam Patel (3), Professor Gerd Schroeder-Turk (1), Professor Bodo Wilts (4)

Affiliations

1. Murdoch University
2. University of California Berkeley
3. University of Chicago
4. University of Salzburg
5. University of Western Australia

Keywords

Hyperspectral imaging

Photonic crystals

Bicontinuous nanosolid

Butterfly wings

Structural colour

Abstract text

Structural colour is a fascinating phenomenon in which colour is produced by nanostructures. Butterflies exemplify the use of structural colour in nature to produce their vibrant colouration. These colours are produced by chitinous nanostructures with varied and sometimes complex morphologies. A particularly remarkable case is that of Erora opisena, which develops labyrinthic photonic crystals with a single Gyroid geometry. In adult E. opisena scales, interference of light with the photonic crystals results in a green coloration and the crystals are organised into micron-sized crystallites with a pronounced size gradient. It is hypothesized that these structures are templated by an organic membrane of corresponding shape, however it is currently not possible to spatially resolve their formation with in vivo imaging methods. Here, we present a hyperspectral microscopy technique that allows in vivo measurements of spatially (~1 µm) and temporally (~3 secs) resolved spectra of developing butterfly wing scales. While the resolution of this technique is not high enough to spatially resolve the underlying nanostructures, our goal is to infer their formation based on the emerging optical signals and to correlate this with conventional SEM and 3D FIB-SEM imaging of samples at key time points. We demonstrate the potential of this technique for in vivo imaging by measuring adult E. opisena wing scales immersed in close-to refractive index matching oils to show that even weak optical signals such as those anticipated to arise from a developing wing scale can be measured using this technique. This raises the hope that our hyperspectral microscopy technique can yield, when applied to a developing pupa, insight into structural colour formation processes in vivo.