Comparison of the effect of constant light on the circadian rhythm of white-eye mutant and wild-type blow fly Protophormia terraenovae

Abstract

Compound eyes of white-eye mutant flies are considered to be more sensitive than those of the wild type because the former lack the screening pigment. The effects of constant light conditions on the circadian rhythm were examined in wild-type and white-eye mutant Protophormia terraenovae to identify plausible photoreceptors mediating constant light to clocks, which affect the free-running period and rhythmicity. Both the wild type and white-eye mutant showed clear rhythmicity under constant light conditions at 0.5 lx and 500 lx. Although the incidence of arrhythmia increased as light intensity increased, more than half of the flies were rhythmic at 500 lx. P. terraenovae seems to have a high threshold for light causing arrhythmia. Incidence of rhythmic flies and the free-running period under constant light conditions were not significantly different between the wild type and white-eye mutant. This suggests that photoreceptors operating under constant light conditions are extraretinal.