Fig. 2: Moth antennal hygrosensory neurons respond to the range of floral humidity presented by Datura flowers.
From: A signal-like role for floral humidity in a nocturnal pollination system
a Zoomed view sequence of electron microscopy images of the styliform complex sensillum on Manduca sexta antenna. The scale bar is shown at the bottom right corner of each image. The image shows two segments of a female antenna and white squares show the location of the styliform complex sensilla on the leading edge of the antenna. b Zoomed view of the entire styliform sensillum surrounded by trichoid sensilla. c Zoomed view of the tip of the styliform sensillum. Black arrow points toward one of the papillae. d A representation of the longitudinal section of the styliform sensillum showing the underlying dendrites and cell bodies based on TEM39,40 and cryosections of the organ. e Schematic of the stimulus delivery setup. Water vapor saturated air at room temperature is sent to two different dewpoint generators, outputting air with fixed relative humidity, RH1 and RH2, corresponding to the ambient temperature, Tamb measured adjacent to the moth. Two electric valves (EV) operated by motors at the outlet of the dewpoint generators regulate the mass flow rate in an antiphase synchronized manner (as shown), which is sent to a thermostatic mixing valve to deliver air with a sinusoidally varying humidity airstream, like the fictive stimulus in (j). Temperature and RH were measured using sensors placed adjacent to the moth antennae. A tungsten electrode was inserted at the sensillum base for electrophysiology. Electrical wirings are denoted in red, and black arrows denote the direction of airflow (see Methods for details). f A humidity stimulus generated by dipping the hygrosensing probe in and out of a Datura flower (see inset illustration) to mimic the humidity experience of moths probing and entering Datura flowers. The blue line shows %ΔRH at 40.6% ambient RH. g Exemplary single sensillum recording of the styliform sensillum (a-d) showing simultaneously recorded extracellular activity of moist and dry neurons (arrows) within a single sensillum. h An overlaid raster plot of the spikes sorted from the raw trace in (g) showing the activity of the moist sensing neuron (blue) and the dry sensing neuron (red). i Moving average of the impulse frequency of the moist (blue) and dry (red) sensing neurons. j A fictive stimulus of floral RH matching the experience of moths probing Datura (shown in f) with the amplitude ranging from 30 to 50% RH and a period of approximately 30 s. k Continuous rate of change in RH across the recording period. l A constant temperature (°C) is maintained across the recording period. Source data are provided as a Source Data file.
