title: Nocturnal illumination dimmer than starlight altered the circadian rhythm of adult locomotor activity of a fruit fly.
abstract: The effects of nocturnal irradiance tenfold dimmer than starlight intensity on the locomotor activity rhythm of Drosophila jambulina were investigated in two types of light-dark (12 h:12 h) cycles, in which light intensity of the photophase was 10 lux while that of the scotophase was either 0 lux for control flies or 0.0006 lux for experimental flies. Activity onset in the experimental flies was approximately 5.4 h prior to lights-on, so it occurred around midnight. However, activity onset of the control flies coincided almost with the lights-on. Nevertheless, activity offset was the same in both groups, occurring at lights-off. Duration of the active phase (alpha) and activity passes/fly/cycle (APC) in the experimental flies was far greater than in controls. After-effects of the nocturnal illumination of the light-dark cycles when the flies were transferred to constant darkness were evident as the period of the free-running rhythm was shortened, alpha was lengthened, and APC was enhanced in the experimental compared to control flies. Thus, very low photic sensitivity of these flies appears to be a physiological adaptation to dim-light ambiance in its natural breeding site in the field.
authors.affiliation: Center for Biological Rhythm Research, Ahmednagar College, Ahmednagar 414001, M.S., India.
authors.forename: Pooja
authors.initials: P
authors.lastname: Thakurdas
authors.forename: Shweta
authors.initials: S
authors.lastname: Sharma
authors.forename: Boynao
authors.initials: B
authors.lastname: Sinam
authors.forename: Meenakshi
authors.initials: M
authors.lastname: Chib
authors.forename: Dilip
authors.initials: D
authors.lastname: Joshi
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology* / Q000528:radiation effects*; D004330:Drosophila / Q000502:physiology* / Q000528:radiation effects*; D008297:Male; D009043:Motor Activity / Q000502:physiology* / Q000528:radiation effects*; D010775:Photic Stimulation; D017440:Photoperiod