Effect of Different Light Regimes on Pre-Adult Fitness in Drosophila melanogaster Populations Reared in Constant Light for over Six Hundred Generations

Abstract

Egg to eclosion development time and survivorship were assayed on four laboratory populations of Drosophila melanogaster that had been reared for over 600 generations in continuous light (LL) and constant temperature. The assays were performed in three environments: continuous light (LL), periodically varying light/dark cycles (LD 12:12 hr), and continuous darkness (DD). Development time in LL was significantly less than that in LD, which, in turn, was significantly less than that in DD, whereas survivorship did not differ significantly among the three treatments. The results indicate that individuals from Drosophila populations routinely maintained in LL do not suffer any deleterious effects of LL treatment on pre-adult fitness. Other studies on these populations have shown that freerunning period (τ) of the eclosion rhythm in DD is greater than that in LD. Our results are, thus, also consistent with the notion that development time may be a function of the free-running period.

Possible role of eclosion rhythm in mediating the effects of light-dark environments on pre-adult development in Drosophila melanogaster

“…On the other hand, environments such as DD and LD cycles, wherein eclosion is rhythmic, the interaction between developmental state and eclosion clock would determine the duration of pre-adult development, and the developmental time would then be expected to be greater than those under LL. In a previous study on four Drosophila populations maintained under LL (JB1..4), the ancestral populations of the flies used in the present study, we had reported shortest development time under LL regime, followed by LD 12:12 h, and DD [14]. In the present study too development time was shortest under LL, followed by T20 , DD, and T24 and T28 , in that order.…”

Extent of mismatch between the period of circadian clocks and light/dark cycles determines time‐to‐emergence in fruit flies

“…Under DD where circadian clocks free‐run with endogenous periodicity close to 24 h, time‐to‐emergence is likely to be determined by the interaction between developmental states of the fly and circadian gating (Qui & Hardin, ), and therefore time‐to‐emergence would be expected to be comparable to that in T24 . Indeed, time‐to‐emergence is found to be shorter under LL compared with T24 and DD (Sheeba et al ., ; Paranjpe et al ., ; Figs. and ).…”

“…Circadian ( circa = about ; dies = a day ) clocks with near 24‐h periodicities regulate behavioral and metabolic processes in a wide variety of organisms (Saunders, ; Dunlap et al ., ). In insects including fruit flies Drosophila melanogaster , these clocks have also been implicated in the regulation of life‐history traits such as preadult development time and adult lifespan (Kyriacou et al ., ; Miyatake, , ; Shimizu et al ., ; Klarsfeld & Rouyer, ; Sheeba et al ., ; Paranjpe et al ., ; Takahashi et al ., ; Yadav & Sharma, 2013, 2014). It is believed that preadult development time of flies with faster circadian clocks is shorter than those with slower clocks.…”

Laboratory Evolution Meets Catch-22Balancing Simplicity and Realism

“…In all these examples, LNS experiments will be selecting on lines that at least initially suffer laboratory induced (if inadvertently so) anomalies or even pathologies, such that the resulting evolutionary trajectories might differ from those of healthy lines. To be sure, lines evolving under constant photoperiod may adapt to such conditions (Sheeba et al 1999), but whether those lines can serve as reliable models for "natural" organisms is uncertain.…”