Developmental time is a fundamental life history trait that affects the reproductive success of animals. Developmental time is known to be regulated by many genes and environmental conditions, yet mechanistic understandings of how various cellular processes influence the developmental timing of an organism are lacking. The nervous system is known to control key processes that affect developmental time, including the release of hormones that signal transitions between developmental stages. Here we show that the excitability of neurons plays a crucial role in modulating developmental time. Genetic manipulation of neuronal excitability in Drosophila melanogaster alters developmental time, which is faster in animals with increased neuronal excitability. We find that selectively modulating the excitability of peptidergic neurons is sufficient to alter developmental time, suggesting the intriguing hypothesis that the impact of neuronal excitability on DT may be at least partially mediated by peptidergic regulation of hormone release. This effect of neuronal excitability on developmental time is seen during embryogenesis and later developmental stages. Observed phenotypic plasticity in the effect of genetically increasing neuronal excitability at different temperatures, a condition also known to modulate excitability, suggests there is an optimal level of neuronal excitability, in terms of shortening DT. Together, our data highlight a novel connection between neuronal excitability and developmental time, with broad implications related to organismal physiology and evolution.
