Light elicited isolation of the complementary visual input systems in white-eye Drosophila.

Evidence is presented to show that the spectral sensitivity of the white-eye of Drosophila, indicated by the residual ERG following blue irradiation which renders the eye dark-depolarized, has a maximum around 460 nm, and represents the activity of R7 and possibly that of R8. Whereas the ERG of the repolarized dark-adapted white-eye, effected by orange irradiation, indicates a spectral sensitivity having a maximum around 490 to 500 nm, and represents the activity of R1 to 6 preferentially. Manipulation of these two visual input systems is achieved using various régimes of irradiation, the systems being switched at will. The critical flicker fusion frequency respectively for the two systems has been measured, that of R1 to 6 being twice as high as that of R7±8.Implications for the visual function of the eye are considered, in particular the significance of the wildtype red-eye colour. The ease of manipulation has considerable value to the experimentalist wishing to study the input systems in isolation and concomitantly.