PIGMENT MIGRATION AND LIGHT-ADAPTATION IN THE EYE OF THE MOTH, GALLERIA MELLONELLA

Abstract

1. An energy flux at the cornea of 5 x 103 ergs sec.-1 cm.-2 at 500 mµ causes almost complete migration of the accessory shielding pigment in the eye of the wax moth, Galleria mellonella. Movement requires approximately 30 minutes. Lower energies bring the pigment to steady-state positions intermediate between the fully light- and dark-adapted positions. 2. Light-adaptation, unlike dark-adaptation, runs a faster time course than pigment migration and is frequently complete in several seconds. This confirms an earlier report of Höglund. The theoretical reasons for a rapid rate of light-adaptation in the face of slow pigment migration are discussed and are shown to be a consequence of (a) equal absorption of the test and adapting lights by the sleeves of accessory pigment, and (b) a linear relation between ΔI and I. 3. It is suggested that the terms, superposition and apposition eye, be replaced by scotopic and photopic eye, as the latter indicate more accurately the physiological properties of these photoreceptors.