Abstract
Drosophila melanogaster females are highly selective about the chemosensory quality of their egg-laying sites [1-6], an important trait that promotes the survival and fitness of their offspring. How egg-laying females respond to UV light is not known, however. UV is a well-documented phototactic cue for adult Drosophila [7-13], but it is an aversive cue for larvae [14-17]. Here, we show that female flies exhibit UV aversion in response to their egg-laying demand. First, females exhibit egg-laying aversion of UV: they prefer to lay eggs on dark sites when choosing between UV-illuminated and dark sites. Second, they also exhibit movement aversion of UV: positional tracking of single females suggests that egg-laying demand increases their tendency to turn away from UV. Genetic manipulations of the retina suggest that egg-laying and movement aversion of UV are both mediated by the inner (R7) and not the outer (R1-R6) photoreceptors. Finally, we show that the Dm8 amacrine neurons, a synaptic target of R7 photoreceptors and a mediator of UV spectral preference [12], are dispensable for egg-laying aversion but essential for movement aversion of UV. This study suggests that egg-laying demand can temporarily convert UV into an aversive cue for female Drosophila and that R7 photoreceptors recruit different downstream targets to control different egg-laying-induced behavioral modifications.
