The optical function of changes in the medium surrounding the cockroach rhabdom

Abstract

In the dark-adapted eye of the cockroachPeriplaneta, the fused rhabdom is surrounded by a clear watery palisade; in the light-adapted eye this is replaced by pigment. The refractive indices of the rhabdom and its surround have been measured. The physiological effects of this change in structure has been analysed by the electromagnetic theory of light guides. The optical constants are theoretically consistent with the measured tenfold change in sensitivity and changes in acceptance angle of the retinula cells from 6.7 ° ¦(dark-adapted) to 2.4 ° (light-adapted). Show more