Behavioral characterization and genetic analysis of the Drosophila melanogaster larval response to light as revealed by a novel individual assay

A new assay was designed, named checker, that measures the individual respo nse to light in the fruitfly Drosophila melanogaster larva. In this assay t he Drosophila larva apparently modulates its pattern of locomotion when fac ed with a choice between a dark and lit environment by orienting its moveme nt towards the dark environment. We show that, in this assay, a response to light can be measured as an increase in residence time in the dark versus the lit quadrant. Mutations that disrupt phototransduction in the adult Dro sophila abolish the larval response to light, demonstrating that this larva l visual function is similar to that of the adult fly. Similarly, no respon se to light was detected in strains where the larval visual system (photore ceptors and target area) was disrupted by a mutation in the homeobox contai ning gene sine oculis (so) gene. Ablation of photoreceptors by the targeted expression of the cell death gene hid under the control of the photorecept or-specific transcription factor glass (gl) abolishes this response entirel y. Finally, we demonstrate that this response to light can be mediated by r hodopsins other than the blue absorbing Rh1.