Abstract
Aedes aegypti (Ae. aegypti) mosquitoes are major vectors of dengue,
chikungunya and other arboviral diseases. Ae. aegypti’s capacity to
reproduce and to spread disease depends on the female mosquitoes’ ability
to obtain blood meals and find water-filled containers in which to lay
eggs (oviposit). While humidity sensation (hygrosensation) has been
implicated in these behaviors, the specific hygrosensory pathways involved
have been unclear. Here we establish the distinct molecular requirements
and anatomical locations of Ae. aegypti Dry Cells and Moist Cells, and
examine their contributions to behavior. We show that Dry Cell and Moist
Cell responses to humidity involve different ionotropic receptor (IR)
family sensory receptors, with dry air-activated Dry Cells reliant upon
the ionotropic receptor Ir40a, and humid air-activated Moist Cells upon
Ir68a. Both classes of hygrosensors innervate multiple antennal sensilla,
including sensilla ampullacea near the antennal base as well as two
classes of coeloconic sensilla near the tip. Dry Cells and Moist Cells
each support behaviors linked to mosquito reproduction, but contribute
differently: Ir40a-dependent Dry Cells act in parallel with
Ir68a-dependent Moist Cells to promote blood feeding, while oviposition
site seeking is driven specifically by Ir68a-dependent Moist Cells.
Together these findings reveal the importance of distinct hygrosensory
pathways in blood feeding and oviposition site seeking, and suggest
Ir40a-dependent Dry Cells and Ir68a-dependent Moist Cells as potential
targets for vector control strategies.