Circadian control of a sex-specific behavior in Drosophila

An endogenous circadian clock controls many of the behavioral traits of Drosophila melanogaster. This 'clock' relies on the activity of interconnected clusters of neurons that harbor the clock machinery. The hierarchy among clusters involved in the control of rest-activity cycles has been extensively studied. Sexually dimorphic behaviors, on the other hand, have received less attention. Even though egg-laying, a female characteristic behavior, has been shown to be rhythmic, it remains largely unexplored possibly due to methodological constraints. The current study provides the first steps towards determining the neural substrates underlying the circadian control of egg-laying. We show that, whereas the lateral ventral neurons (LNvs) and the dorsal neurons (DNs) are dispensable, the lateral dorsal neurons (LNds) are necessary for rhythmic egg-laying. Systematically probing the Drosophila connectome for contacts between circadian clusters and oviposition-related neurons, we found no evidence of direct connections between LNvs or DNs and neurons recruited during oviposition. Conversely, we did find bidirectional connections between two Cryptochrome (Cry) expressing LNd (Cry + LNds) and oviposition-related neurons. Taken together, these results reveal that Cry + LNd neurons have a leading role in the control of the egg-laying rhythm in Drosophila females.