Discontinuity of the Excitation Process in Locust Visual Cells

Abstract

By way of introduction, we may select and draw attention to one or two specialized features of the arthropod visual receptor system that seem of general interest. First, in the compound eye receptors, the photosensitive pigment system is contained in a membranous apparatus derived from, and in clear anatomical continuity with the limiting cell membrane. Either the microvillar border of the cells, termed the rhabdomere, or the remainder of the unspecialized membrane of the receptor somas, mediates the familiar active electrical illumination responses. On an intuitive level at least, it is easier to speculate about the nature of the processes that mediate between photolysis of the carotenoid photopigment and the development of the electrical response—the problem that exists in the vertebrate retina regarding spatial transmission of excitation from the rod lamellae eventually to the rod-bipolar synapse does not exist in such acute form here.