Long-term adaptation by different monochromatic light in the photoreceptors of three crustacean species

Abstract

Long-term adaptation by monochromatic light of different wavelengths and equal stimulus efficiency was tested in the photoreceptors of Carcinus (= Carcinides) maenas L., Eupagurus bernhardus L., and Astacus leptodactylus Eschscholz. The characteristic course of light and dark adaptation was compared for these species. Addition of glucose in the saline caused faster dark adaptation, probably due to electrogenic pump activity. Adaptation effects by weak and stronger light were equal for all wavelengths used (between 409 and 611 nm). The results indicate that the observed light and dark adaptation consists both in pigment and in membrane adaptation. Photoreversal of bleaching could not be proved. The results with Astacus can be explained by photoreversal and/or by selective adaptation of two different receptors of different spectral sensitivity. In Eupagurus colour vision seems to be improbable.