Adaptation in the Compound Eye and Interaction with Screening Pigment
The electroretinogram pattern in the compound eye of T. molitor and the appearance of irregular small potentials and spikes superimposed on the ERG are influenced during dark and light adaptation procedures. The amplitude of the principal negative potential reflects bleaching and recovery of the photochemical process. This is not true for the latency values. The delay of the electrical response increases in the dark and decreases in the light adapted eye. These changes were influenced by the intensity of the adapting light. Mutant eyes only lack screening pigment and have normal visual neural pathways. The absence of this pigment lowered the threshold sensitivity of the unscreened eye in dark adaptation. The difference between the adaptation processes in mutants and normal animals has been suggested as a criterion for measuring the net effect of the screening pigment in the compound eye.