Selection for early and late adult emergence alters the rate of pre-adult development in Drosophila melanogaster

Abstract

BackgroundCircadian clocks have been implicated in the regulation of pre-adult development of fruit flies Drosophila melanogaster. It is believed that faster clocks speed up development and slower clocks slow it down. We established three sets of D. melanogaster populations (early, control and late). The early and late populations were raised by selecting for flies that emerged either in the morning or in the evening under 12:12 hr light/dark (LD) cycles. After 75 generations of selection, the time course and waveform of the adult emergence and activity rhythms of the early and the late populations diverged from each other as well as from the controls. In this paper, we report the consequence of this selection on the rate of pre-adult development.ResultsWe assayed the pre-adult development time of the selected and control populations under 12:12 hr LD cycles and constant darkness (DD). Under LD cycles, the early populations develop faster than the controls, while the late populations develop slower than the controls. Although flies take longer to develop under DD than in LD, the relative differences between the mean development times of the selected and control populations remain unaltered in DD. In a separate experiment designed to investigate the effect of time of egg collection and experimental conditions on the duration of pre-adult stage, we assayed the development time of the selected and control populations by collecting eggs at different times of the day (morning and evening) and by assaying their pre-adult development time under constant light (LL), LD, and DD conditions. Irrespective of the time of egg collection and assay light regime, the late flies continue to develop slower than the early flies.ConclusionThe results of our study clearly indicate that selection on the timing of adult emergence alters the rate of pre-adult development in D. melanogaster. The timing of egg collection as well as assay light regime does not have any measurable effect on the relative differences between the developmental rates of the early and the late flies. Taken together these results appear to suggest that pleiotropic effects of clock genes mediate correlated changes in the timing of adult emergence and the rate of pre-adult development in D. melanogaster.

Life-history traits of Drosophila melanogaster populations exhibiting early and late eclosion chronotypes

“…Since eggs for the egg-to-puparium and egg-to-adult duration assays were collected from all populations at the same time (thus were age matched), the observed differences in pre-adult duration between the early and the late populations are unlikely to be due to the differences in the age of eggs. Moreover, the time of egg-collection or the age of eggs does not alter the difference in egg-to-adult duration between the early and the late populations [ 45 ]. Taken together these results suggest that difference in pre-adult developmental rates of the early and the late populations is not entirely circadian clock driven, and may also involve clock independent mechanisms which might drive differential interaction with LD cycles (significant population × light regime interaction reported in Table 1a , c ).…”

Larks, owls, swifts, and woodcocks among fruit flies: differential responses of four heritable chronotypes to long and hot summer days

“…Although the division into “larks” and “owls” was previously explored, it was only in the studies of early and late eclosion chronotypes. 14 As for the studies of sleep–wake typology in D. melanogaster , the previously published reports focused on the distinction between the types of short and long sleepers 15 rather than between the birds of different feathers.…”

Gene Expression Associated with Early and Late Chronotypes in Drosophila melanogaster

“…Importantly, while most flies eclose during dawn, a small proportion of flies often eclose at substantially delayed times ( 11 ). Furthermore, using artificial selection, it is possible to select for early and late eclosion chronotypes ( 12 ), indicating that there is a sizeable genetic component underlying variation in diurnal preference. Here, we have screened the Drosophila genetic reference panel, a suit of isogenic strains originated from the same wild population, whose complete genome has been sequenced ( 13 ).…”