Quantitative response to photoperiod during reproductive diapause in the Drosophila auraria species-complex

Abstract

In Drosophila auraria, D. biauraria, D. triauraria and D. subauraria which entered reproductive diapause in response to short photoperiods, the phase sensitive to photoperiod for induction of diapause extended from the pre-imaginal stage to the imaginal stage. In the vicinity of the critical photoperiods, a shorter photoperiod was more effective in inducing diapause in these species, whereas a longer photoperiod was more effective in averting diapause and also hastening ovarian development. In these species, diapause was intensified after eclosion usually to a higher degree at a shorter photoperiod, whereas it was weakened at a photoperiod close to the critical photoperiods. It is assumed that the mechanism of diapause induction functions at every photoperiod, but with a greater efficiency or to an older age at a shorter photoperiod. Then, diapause prevention at a long photoperiod is understood to be due to the ending of the induction process before the determination of diapause, whereas deeper diapause at a shorter photoperiod is to the more efficient and longer induction. The timing and degree of intensification of diapause varies among species, geographic strains, or individuals within a strain.