Interactive effect of photoperiod and temperature on the induction and termination of embryonic diapause in the migratory locust.

Abstract

Diapause plays a vital role in the survival and population reproduction of the migratory locust in temperate regions. Although some studies have suggested that photoperiod and temperature are two important environmental factors involved in the induction and termination of embryonic diapause in locusts, the independent or synergetic roles of these two factors are still unclear. We designed crossover experiments to investigate the effects of photoperiod, temperature and treatment time on the induction and termination of embryonic diapause in locusts by optical coherence tomography (OCT), which can track the entire embryonic developmental process via noninvasive 3D real-time imaging. Diapause induction experiments showed that a short photoperiod (in adults) and a low egg treatment temperature are the most important prerequisites for inducing egg diapause. The diapause rate reached 90.7% when the adults were reared under a short photoperiod (8 L:16 D) and the eggs were treated at 22 °C. However, the adult rearing temperature had no significant effect on diapause induction. Analysis of variance also confirmed that there was a significant interactive effect between parental photoperiod and egg treatment temperature. Moreover, diapause termination experiments showed that 13 °C (near the developmental threshold temperature of 15 °C) for 20 days is the most effective condition for terminating diapause. Our study provides accurate photoperiod and temperature thresholds for inducing and terminating diapause in the migratory locust, suggesting potential applications in the prediction and control of locust plagues. © 2021 Society of Chemical Industry.