Does the difference in the timing of eclosion of the fruit fly Drosophila melanogaster reflect differences in the circadian organization?

The eclosion rhythm of a laboratory population of Drosophila melanogaster w as studied under 12h light, 12h dark (LD 12:12) cycles. Although most of th e flies were found to eclose just after "lights on" in LD 12:12, termed wit hin gate (WG) flies, a few flies were found to eclose nearly 10h after peak eclosion, termed outside gate (OG) flies. The circadian parameters of the clocks controlling oviposition rhythms in the WG and the OG flies were esti mated to understand the cause of such differences in the timing of eclosion . The distribution of the fraction of individual flies exhibiting single, m ultiple, and no significant period in the WG flies was significantly differ ent from distribution in the OG flies. Compared to the WG flies, more OG fl ies were found to exhibit oviposition rhythm with multiple periodicity, whe reas more WG flies exhibited an oviposition rhythm with a single significan t period. The fraction of flies with arrhythmic oviposition was similar in both the WG and the OG flies. Free-running period tau in constant darkness (DD) and the phase angle difference psi in LD 12:12 for the oviposition rhy thm of WG and OG flies were significantly different. These results suggest that the differences in the time of eclosion between the flies eclosing wit hin the gate and outside the gate of eclosion are probably due to differenc es in the circadian system controlling eclosion, which is reflected by the differences in their oviposition rhythm.