Persistence of oviposition rhythm in individuals of Drosophila melanogaster reared in an aperiodic environment for several hundred generations

The oviposition rhythm of individual flies of Drosophila melanogaster from a population maintained in an aperiodic environment (with light, temperatur e, humidity, and other factors which could provide time cues, kept constant ) for several hundred generations was assayed in constant light (LL), in li ght/dark (LD 12:12 hr) cycle, and in constant darkness (DD). More than 50% of the flies assayed exhibited rhythmicity in oviposition in all three ligh t regimes. The results indicate that the phenomenon of egg laying is rhythm ic in individual D. melanogaster females and is controlled by an endogenous time keeping mechanism. The persistence of the oviposition rhythm in a lar ge proportion of individuals in the population after several hundred genera tions of rearing in a constant environment strengthens the view that posses sing biological clocks may confer some intrinsic fitness advantage even to organisms living in aperiodic environments. J. Exp. Zool. 290:541-549, 2001 . (C) 2001 Wiley-Liss, Inc.