“White Eye” as a Model for Study of Optical Properties of Visual Pigments in Insects

Abstract

Using an accurate spectral scan method, spectral sensitivity curves (SSCs) of photoreceptors of non-pigmented (“white”) eyes of eye-colour mutants were measured in the honeybee, Apis mellifera, and two species of flies, Calliphora erythrocephala and Drosophila melanogaster. In all the species, the dominating photoreceptors, long-wave in the honeybee and cells 1–6 in flies, displayed their SSCs narrower then it should have been expected from the absorption spectra of their starting visual pigments. Two explanations could account for this finding: i) there exists a natural difference between the absorption spectra of visual pigments in insects and their vertebrate counterparts, and ii) “white eyes” are slightly coloured with auxiliary pigments still unknown which make the SSCs to be narrower in mutants; if so, the “white eye” of mutants should not be considered really white.