A dynamic humidity arena to explore humidity related behaviours in insects

Abstract

Humidity is a critical environmental factor influencing the behaviour of terrestrial organisms. Despite its significance, the neural mechanisms and behavioural algorithms governing humidity sensation in insects remain elusive. In this study, we introduce a novel dynamic humidity arena to investigate humidity-guided behaviour in the vinegar fly Drosophila melanogaster. The arena allows precise humidity control, low error rates, and fast settling times, making it a robust tool for studying humidity-related behaviours. Our results reveal that desiccated and starved flies (DS flies) search for higher relative humidity environments (65-75%) while sated flies tend to stay within their initial environments. In contrast, Ionotropic receptor (Ir)93a mutant flies with impaired humidity sensing show no preference to relative humidity. The search for higher humidity in DS flies is reflected in their relatively high displacement and walking speed compared to control and mutant flies. Our novel method manipulates humidity cues to create complex humidity landscapes that respond in real-time to insect movement. This will help us shed light on how humidity shapes behaviour and offers a foundation for further research in the field of hygrosensation.