Photoperiodism and time measurement in the parasitic wasp, Nasonia vitripennis

Abstract

Daily periods of chilling, abnormal light/dark cycles, and “night interruption’ experiments were used to gain information about the photoperiodic clock in Nasonia vitripennis. Using abnormal LD cycles, a high rate of induction of larval diapause was only obtained within a narrow range of cycle lengths (21–26 hr) regardless of whether the light or the dark component was the longest. Chilling for 4 hr daily, in the light, reversed the photoperiodic effect of LD 16 : 8 and shifted the first peak of diapause inhibition 2 hr to the right in LD 14 : 10. Shortening the main light component of LD 14 : 10 to LD 11·3 : 10 also shifted the first peak of diapause inhibition to the right, showing that time measurement begins with lights-on rather than with lights-off. These results are regarded as strong circumstantial evidence for the involvement of a circadian rhythm in the Nasonia photoperiodic clock.