SENSITIVITY OF THE LABELLAR SUGAR RECEPTORS OF PHORMIA-REGINA IN RELATION TO FEEDING

The hypothesis that behavioural feeding threshold of P. regina modulates and is modulated by the sensitivity of the labellar contact chemoreceptors is not supported by the examination of individual flies. Sensitivity (number of impulses fired in the first second of stimulation) of the sugar receptors in selected labellar hairs of flies of known age was recorded periodically on a fixed schedule for up to 72 hr. Experimental flies were hand fed 2.0 M fructose once every 24 hr. No correlations between feeding or age and receptor sensitivity were found. Statistically significant changes in firing frequency did occur but were unrelated to feeding and age. The proboscis extension response, on which behavioural threshold measures are based, is known to be triggered by the first few sugar receptor spikes of sufficient frequency. Neither age nor feeding significantly affected the number or frequency of impulses during the first 50 msec of stimulation. © 1979.