Rapid active-reflection display on dorsal stripes of Atherinomorus lacunosus

Abstract

A large number of living creatures are able to use environmental light effectively as a biological display. The biological structural colors are very attractive not only within the coloring species but also to humans. However, the detailed function of bio-reflectors, which constitute the structural color with respect to communication, remains unknown. Atherinomorus lacunosus has alignments of iridophore spots on its dorsal part. Here it is found that a spot with a diameter of approximately 0.1 mm causes a rhythmic blinking of light owing to rapid reflection changes in iridophores existing inside the spot. The iridophores contain reflecting particles which show similar rotational responses to magnetic field under a light exposure. The speed of the intensity change of light at a frequency of approximately 1 Hz is proposed to be controlled by the nervous system of A. lacunosus. This kind of passive illumination may contribute to the development of a new optical device with low energy consumption.