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The song of love [electronic resource] : the afferent auditory pathway in Drosophila melanogaster

This thesis encompasses three projects at the intersection of genetics, behavior, and neurobiology in the fruitfly, Drosophila melanogaster. The major work presented is an investigation of the afferent auditory system in D. melanogaster. The afferent auditory system of D. melanogaster arises from the Johnston's Organ in the second antennal segment, from which mechanosensory neurons project to a protocerebral region known as the Antennomechanosensory and Motor Complex (AMMC). The antennal mechanosensory system in Drosophila is used in multiple contexts, including vestibular mechanosensation, wind sensitivity, and courtship hearing. During courtship, male flies present a stereotypic pulse song as well as a hum-like sine-song to female flies; these stimuli are species-specific and critical to female receptivity. Using a large enhancer-Gal4 collection, I identify 12 candidate cell types within the AMMC, divided into 7 types of projection neurons as well as 5 types of local AMMC interneurons. I tested each of these cell types for its effect on courtship hearing by testing the effect of neuronal silencing on a) female receptivity, and b) a male locomotor response (Song-Induced Locomotion). These tests reveal that the activity of one class of projection neuron (aPN1), and one class of local interneuron (aLN(al)) are critical to courtship hearing in both male and female flies. Other cell types appear to be dispensable for courtship hearing, and may play a role in non-courtship related mechanosensation. To help confirm that these phenotypes are not specific to neuronal silencing, I also hyperactivated each cell type using the temperature-sensitive dTrpA1 reagent; these results confirm that aPN1 and aLN(al) alone are necessary for courtship hearing. Overall this work identifies a set of parallel pathways from the AMMC leading to the ventrolateral protocerebrum (VLPR), but reveal that only one of these pathways is necessary for courtship hearing. The structure of this circuit is analogous to the multi-lineage projection identified in D. melanogaster olfaction, in which a parallel pathways share a common projection but carry independent information. In addition to this work, I also discuss an investigation of the role of abnormal-chemosensory jump 6 (acj6) on escape behaviors, as well as an investigation of the expression of doublesex (dsx) in the nervous system.