Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly, Delia antiqua: the effect of thermoperiod.

When non-diapause and diapause pupae of Delia antiqua were exposed to various thermoperiods where thermophase (T) was 25 degrees C and the cryophase (C) was 15 or 20 degrees C (TC(15) or TC(20)) in constant darkness (DD), the majority of both types of flies emerged before the rise in temperature. Eclosion time was delayed at the lower cryophase temperature. Moreover, there was a significant difference in the time of adult eclosion between non-diapause and diapause pupae; diapause pupae eclosed earlier than non-diapause pupae. When the two types of pupae were transferred to a constant low temperature (15 or 20 degrees C) after having experienced TC(15) or TC(20) 12:12 h, they showed circadian rhythmicity in eclosion. The free-running period (tau) of the eclosion rhythm changed after transfer to constant low temperatures in both non-diapause and diapause pupae, suggesting that this change represents a transient cycle until the temperature-sensitive oscillator is coupled again to the temperature-insensitive pacemaker. However, diapause pupae tended to show a shorter tau than non-diapause pupae. This observation suggests that the difference in adult eclosion time under thermoperiodic conditions between non-diapause and diapause pupae is related to their different tau s.