In search of the sixth sense: Untangling the mechanism of hygrosensation

Humidity is an climatic factor that influences behaviour of land-living animals.

Insects in particular use humidity cues to navigate, for example disease-vectors such as mosquitoes use this sense to find hosts to bite. Recently, I identified the hygrosensory organ in the vinegar fly Drosophila melanogaster.

These studies revealed that humidity receptor neurons (HRNs) are shielded from exposure to air and submerged in sensillar lymph.

How can a sensory receptor that is shielded from air and submerged in an aqueous solution detect fluctuations in the concentration of water molecules in the air? Answering this question is fundamental for understanding hygrosensation.

A prevailing hypothesis is that HRNs detect an indirect feature of humidity fluctuation such as mechanical, osmotic or temperature changes.

With this proposal I aim to unravel the transduction mechanism of hygrosensation by testing this hypothesis at three levels of inquiry: the ultrastructural level to identify humidity-induced structural dynamics in hygrosensilla, the cellular level to determine which stimulus HRNs detect and how humidity information is encoded, the molecular level to identify the molecules and mechanism of hygrosensory transduction.

Together, these data will allow me to present a unified model of how insects sense humidity.

Unravelling the enigmatic mechanism of hygrosensation would be a significant advance for neuroscience, extending our understanding of the sensory world of animals.