RESUMO
The daily patterning of animal behaviour is presumed to be due to changes in responsiveness to external stimuli, as a function of varying internal states which may be oscillating with a 24 h period. The endogenous circadian system functions to organize behaviour and physiology to adapt to and anticipate environmental changes in light, temperature, food and mate availability. Light is most important zeitgeber that influence circadian physiology of several insects. The present study is an attempt to understand the eclosion behaviour of Drosophila melanogaster (Oregon-K strain), Drosophila gangotrii and Drosophila jambulina under light/dark (LD), continuous light (LL), continuous dark (DD) conditions for 30 generations. The stocks were maintained at 20±1 °C with 75% RH. Eclosion behaviour was analyzed at 4 h intervals until complete emergence of flies. Result reveals that in all the species peak of eclosion was found at dawn and on subjective day. Intraspecies comparison shows that there was no significant difference in eclosion at different time point and generations under different light regimes. However, interspecies comparison shows significant difference for hours. The data from experiments showed altered rhythm in the form of phase advance and phase delay in eclosion at different light regimes suggesting the role of photoperiod in the physiology of organisms.