Abstract
BackgroundCircadian clocks have been postulated to regulate development time in several species of insects including fruit flies Drosophila melanogaster. Previously we have reported that selection for faster pre-adult development reduces development time (by ~19 h or ~11%) and clock period (by ~0.5 h), suggesting a role of circadian clocks in the regulation of development time in D. melanogaster. We reasoned that these faster developing flies could serve as a model to study stage-specific interaction of circadian clocks and developmental events with the environmental light/dark (LD) conditions. We assayed the duration of three pre-adult stages in the faster developing (FD) and control (BD) populations under a variety of light regimes that are known to modulate circadian clocks and pre-adult development time of Drosophila to examine the role of circadian clocks in the timing of pre-adult developmental stages.ResultsWe find that the duration of pre-adult stages was shorter under constant light (LL) and short period light (L)/dark (D) cycles (L:D = 10:10 h; T20) compared to the standard 24 h day (L:D = 12:12 h; T24), long LD cycles (L:D = 14:14 h; T28) and constant darkness (DD). The difference in the duration of pre-adult stages between the FD and BD populations was significantly smaller under the three LD cycles and LL compared to DD, possibly due to the fact that clocks of both FD and BD flies are driven at the same pace in the three LD regimes owing to circadian entrainment, or are rendered dysfunctional under LL.ConclusionsThese results suggest that interaction between light regimes and circadian clocks regulate the duration of pre-adult developmental stages in fruit flies D. melanogaster.
Highlights
Circadian clocks have been postulated to regulate development time in several species of insects including fruit flies Drosophila melanogaster
The pupal stage starts after the third instar larval stage, lasts for another 4 days, subsequently leading to wing-pigmentation followed by adult emergence, the entire pre-adult developmental duration of Drosophila spans ~9 days
While adult emergence in insects including Drosophila is under the control of circadian clocks [17,18,19], evidence suggests that clocks begin ticking in the fly as early as the third instar larval stage and is functional for the most part of pre-adult development [20,21,22,23]
Summary
Circadian clocks have been postulated to regulate development time in several species of insects including fruit flies Drosophila melanogaster. We have reported that selection for faster pre-adult development reduces development time (by ~19 h or ~11%) and clock period (by ~0.5 h), suggesting a role of circadian clocks in the regulation of development time in D. melanogaster We reasoned that these faster developing flies could serve as a model to study stage-specific interaction of circadian clocks and developmental events with the environmental light/dark (LD) conditions. Studies on insects including Drosophila have reported rhythmicity in several developmental events such as egg-hatching [12,13], pupation [14,15] and wing-pigmentation [2,16], implying a role of circadian clocks in timing pre-adult stages. While it is known that the duration of pre-adult development would be greatly affected by environmental LD cycles [8,27,28], which of the developmental stages would be affected the most is still unknown
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