PHOTOMECHANICAL RESPONSES OF THE PROXIMAL PIGMENT IN PALAEMONETES AND ORCONECTES

Abstract

The proximal retinal pigment of Palaemonetes vulgaris more closely approached the light-adapted position when the prawns were on a white background than on a black background under the same incident light intensity. The black background functioned merely to decrease the brightness of the visual field. The proximal pigment in Palaemonetes and Orconectes vulgaris kept in darkness overnight showed a greater light-adaptational response after exposure to a high-intensity stimulus than specimens that had been under a low intensity of illumination prior to the bright light. These findings support the hypothesis that light-adaptation of the proximal retinal pigment, following a dark-to-light change, is due to discharge of light-adapting hormone.