title: Low rates of change enhance effect of humidity on the activity of insect hygroreceptors.
abstract: The inability to measure humidity during stimulation has so far prevented us from understanding the contribution of moist cells and dry cells to orientation in a gradient of humidity. The problem was solved in the present study by means of a UV-absorption hygrometer that made it possible to monitor humidity at a rate of 100 Hz. The antennal moist and dry cells of the cockroach were exposed to humidities alternatively falling or rising at low rates between -1% RH s(-1) and +1% RH s(-1) (relative humidity). Impulse frequency of both types of cells depended simultaneously on instantaneous humidity and its rate of change. High frequencies of the moist cells signal high humidity. But at a given humidity, the response frequency is higher still when humidity is also rising. Conversely, high frequencies of the dry cell signal low humidity, and frequency is higher still at a given humidity when humidity is also falling. These responses ensure that the cockroach spent a minimum time in environments where desiccation or hydration occur and may thus protect the animal from emerging accidentally from under cover into moving air. In the constant-humidity retreat of the cockroach, fluctuating or even drifting discharge frequencies could serve as an early warning: return!
authors.affiliation: Institut of Zoology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria. harald.tichy@univie.ac.at
authors.forename: H
authors.initials: H
authors.lastname: Tichy
mesh_terms: D000818:Animals; D002628:Chemoreceptor Cells / Q000502:physiology*; D006813:Humidity; D008297:Male; D010526:Periplaneta / Q000502:physiology*; D012679:Sense Organs / Q000166:cytology / Q000502:physiology