Parametric effects of light acting via multiple photoreceptors contribute to circadian entrainment in Drosophila melanogaster

Circadian rhythms in physiology and behavior have near 24-hour periodicities that must adjust to the exact 24-hour geophysical cycles on earth to ensure adaptive daily timing. Such adjustment is called entrainment. One major mode of entrainment is via the continuous modulation of circadian period by the prolonged presence of light. Although Drosophila melanogaster is a prominent insect model of chronobiology, there is little evidence for such continuous effects of light in the species. In this study, we demonstrate that prolonged light exposure at specific times of the day shapes the daily timing of activity in flies. We also establish that continuous blue- and UV-blocked light lengthens the circadian period of Drosophila and provide evidence that this is produced by the combined action of multiple photoreceptors which, includes the cell autonomous photoreceptor cryptochrome. Finally, we introduce ramped light cycles as an entrainment paradigm that produces light entrainment that lacks the large light-driven startle responses typically displayed by flies and requires multiple days for entrainment to shifted cycles. These features are reminiscent of entrainment in mammalian models systems and make possible new experimental approaches to understanding the mechanisms underlying entrainment in the fly.All files are MS Excel sheets and can be opened with any spreadsheet program. There is one file for each figure of the manuscript which contains all the data used to make the plots and perform downstream analyses.Funding provided by: National Institute of Neurological Disorders and StrokeCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000065Award Number: R01NS077933All data were collected using Drosophila Activity Monitors (as described in the methods section of our manuscript). Processed data are uploaded as a compressed file