Song Patterns and Song Patterning Neurons of Drosophila melanogaster

Abstract

Throughout the animal kingdom, mate selection primarily relies on decision-making, and a number of species rely on acoustic signals as an important sensory cue to inform their de- cisions. The courtship song production and recognition circuits in the small and genetically tractable nervous system of the fruit fly Drosophila melanogaster provides an excellent model for studying the principles underlying song pattern generation and decision-making.

The sensory environment influences courtship songs of D. melanogaster. D. melanogaster are ectotherms, unable to regulate their body temperature. Temperature is known to affect biological processes and thus changes in temperature may impact the ability of males to effec- tively communicate if song parameters change in a temperature-dependent manner. I find that that a variety of song features change with temperature. I also identify that pulse train duration is temperature compensated and that this arises from the interaction between a de- crease in IPI and pulse width at higher temperature with an increase in the number of pulses per train at higher temperatures.

To identify the neurons involved in song production in Drosophila, I conducted a neu- ral activation careen. Several neuronal classes (in the brain and ventral nerve cord (VNC)) involved in song production in D. melanogaster had already been identified. However, pre- vious work had focused only on neurons expressing two transcription factors, fruitless (fru), and doublesex (dsx), known to play a role in courtship behavior and sexual dimorphism of the nervous system. As such these screens were not comprehensive. The functional properties and connectivity of these neurons also remained uncharacterized in both males and females. I perform an unbiased screen for additional song production neurons in the VNC, where the putative song pattern generating circuit for D. melanogaster resides. My data identify novel components of the song production circuit that are both fru- and dsx-expressing and non fru- and non dsx-expressing. I establish that some of these neurons are functionally connected to previously identified song command neurons in the brain. I also used a stochastic labeling strategy to identify the song production neurons in genetic enhancer lines. Finally, I exam- ined the necessity of these neurons for song production, and studied their morphology in females.