||Resetting of the circannual rhythm of the varied carpet beetle Anthrenus verbasci by low-temperature pulses
Miyazaki, Yosuke ,
Watari, YasuhikoNumata, Hideharu
399 , 2016-12 , Wiley-Blackwell
The varied carpet beetle Anthrenus verbasci L. has a circannual pupation rhythm and pupates in the spring in the wild. The change in photoperiod acts as a predominant zeitgeber for this rhythm. However, it is unclear whether the change in ambient temperature acts as a zeitgeber. The present study examines the effects of low-temperature pulses on this circannual rhythm by exposing larvae kept under constant short-day conditions (LD 12 : 12 h) at 20°C to a lower temperature of 15, 10 or 5°C for 8 or 12 weeks at various phases. Larval development and pupation are suppressed during exposure to low temperature, with this pupation being induced in sufficiently grown larvae within 2 months of a return to 20°C. These results are attributed to the exogenous suppression and stimulation of pupation, rather than being related to the circannual rhythm (i.e. masking of the circannual rhythm by temperature). Furthermore, long-term observations demonstrate the existence of phase-dependent phase shifts of circannual rhythm as a result of low-temperature pulses. Circannual phase response curves to low temperature are constructed on the basis of the phase shifts obtained. A low-temperature pulse as a winter signal can reset the circannual rhythm of A. verbasci. It is probable that both temperature and photoperiod play a role in the entrainment of this circannual rhythm to a natural year.