Many variations on a few themes: a broader look at development of iridescent scales (and feathers).

Iridescent structures are some of the most visually stunning phenomena in biological organisms. Insects and birds have in common the display of such colours in their non-living investiture, the scales and bristles in insects and the feathers in birds. The biological mechanisms underlying the formation of these structures, at least in insects, appear quite conservative in that the same architect, the eukaryotic cell, can produce not only the iridescent structure but, with some tweaking of the genome, other structures as well, a fact that may be of particular interest to materials scientists and industrial parties seeking to biomimic these forms. Here, we review two examples, one on the cellular and the other on the subcellular level of this developmental flexibility in insects. We then go on to review what is known about iridescent feather development in birds. We suggest that, in view of the increasing evidence that genes and pathways are conserved among taxa, the work on insects may perhaps suggest perspectives or directions of potential use in the study of birds.