Movement of Retinula Cells in Insect Eyes on Light Adaptation

Abstract

THE sensitivity of insect compound eyes to light varies with the previous illumination of the animal. A dark adapted eye has a lower threshold to light than the light adapted eye. Despite models¹ which suggest a simple cause of this change, several factors are clearly at work. A rapid change in sensitivity occurs in the primary receptors themselves²: slower changes in sensitivity have been ascribed to pigment movements³., and changes in field size to movement of mitochondria and endoplasmic reticular spaces⁴. In the course of studies⁵ on the physiology of the retina of Dytiscus marginalis, I have discovered that light and dark adaptation is accompanied by large movements of the retinula cells. Examination of the retina of the giant water bug, Lethocerus americanus, has revealed a similar phenomenon.