Volatile Anesthesia Reveals Independent Regulation of Circadian Rhythms and Photoperiodic Response in a Wasp

Photoperiodism, the ability to respond to changes in day length, enables many temperate organisms to adapt their life cycles to seasonal variations. Although considerable research has focused on the molecular mechanisms of the circadian clock in photoperiodism, the relationship between the clocks that govern daily behavioral rhythms and the photoperiodic response remains unclear. Here, we used the volatile anesthetic agent isoflurane to investigate this relationship in the parasitic jewel wasp, <i>Nasonia vitripennis</i>. Six hours of isoflurane anesthesia (IA) during the first (Zeitgeber time [ZT] 0) and second halves (ZT 6 and 8) of the photophase induced a phase delay and a phase advance in the activity onset, respectively, while IA at these ZTs followed by dark and light cycles cancelled the IA-induced phase shifts. Interestingly, daily IA treatment during the second half of the photophase (ZT 8) increased the incidence of diapause. These results indicate that IA affects both locomotor activity rhythms and photoperiodic responses, but in an inconsistent manner. The clock that regulates the daily activity rhythms operates independently of the system controlling photoperiodic response in this species.