Discovery of functional iridescence and its coevolution with eyes in the phylogeny of Ostracoda (Crustacea)

Abstract

Highly efficient iridescence caused by natural diffraction gratings is reported for the first time in the Crustacea. Iridescence presumably began as an epiphenomenon, but has evolved to include a courtship function in at least some myodocopid Ostracoda (Crustacea). Ostracod iridescence apparently preceded the evolution, and is probably a precursor, of cypridinid (Myodocopida) bioluminescence. By tracing the development of light reception and display, myodocopid evolution, in part at least, is revealed. Therefore, light appears to be the main stimulus to myodocopid evolution. The myodocopid lateral eye probably evolved at a similar point in time as iridescence, possibly to detect iridescence. The graduations by which the ostracod compound eye has developed are suggested. These findings challenge current theories which demand a single evolution of the compound eye.