title: Environmentally-induced modulations of developmental rates do not affect the selection-mediated changes in pre-adult development time of fruit flies Drosophila melanogaster.
abstract: In a previous study we had shown that 55 generations of selection for faster egg-to-adult development in fruit flies Drosophila melanogaster results in shortening of pre-adult duration by ~29-h (~12.5%) and speeding-up of circadian clock period (τ) by ~0.5-h, implying a positive correlation between development time and τ. In Drosophila, change in ambient temperature is known to alter the rate of pre-adult development but not the speed of circadian clocks whereas 12:12-h warm/cold (WC) cycles are likely to alter both pre-adult development rate and τ (via entrainment). To study the effect of overall speeding-up/slowing-down of pre-adult development and circadian clocks on the selection-mediated difference in pre-adult development time, we subjected developing flies to the following conditions: (i) different ambient temperatures (18, 25 and 29°C) under constant darkness (DD) to alter the rate of pre-adult development, or (ii) cyclic WC conditions (WC1-25:18 or WC2-29:25°C) to alter rate of development and τ. The results revealed that the selected (FD) stocks develop faster than controls (BD) by ~52, 28 and 21-h, at 18, 25 and 29°C, respectively, and by 28 and 26-h under WC1 and WC2, respectively. The τ of activity/rest rhythm decreased considerably at 18°C but it did not differ between the FD and BD flies, which suggests a break-down of correlation between development time and τ, seen under their normal rearing conditions (constant darkness--DD at 25°C). While the absolute difference in development time between FD and BD stocks increased or decreased under cooler or warmer conditions, the relative difference in their pre-adult development time remained largely unaltered. These results suggest that manipulations in ambient conditions independently changes development time and τ, resulting in a break-down of the genetic correlation between them.
authors.affiliation: Chronobiology Laboratory, Evolutionary and Organismal Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur PO, Bangalore, Karnataka, India.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Yadav
authors.forename: Vijay Kumar
authors.initials: VK
authors.lastname: Sharma
mesh_terms: D000818:Animals; D057906:Circadian Clocks / Q000528:radiation effects; D004331:Drosophila melanogaster / Q000737:chemistry / Q000254:growth & development* / Q000502:physiology / Q000528:radiation effects; D017753:Ecosystem; D004777:Environment; D005260:Female; D007700:Kinetics; D008297:Male; D017440:Photoperiod; D013696:Temperature