Mechanism of JH influence on the function of labellar chemosensilla in Phormia: experimental suggestions.

The aim of this research study was to determine at which level the JH effect of increasing chemosensillar sensitivity in Phormia could take place. Two-day-old adult female Phormia regina (Meigen) flies were used. Variations in electrical resistance and spike firing frequency of labellar chemosensilla stimulated with NaCl solutions were measured before and after topical application of a JH analogue (JHA). Variations in the above two parameters were also determined in a group of control flies. Results showed that an inverse linear relationship exists between electrical resistance and spike firing frequency in both JHA-treated and control flies. On this basis, we conclude that the above sensitivity variations depend on a mechanism common to both groups of flies. As regards the mode of action of this mechanism, we suggest that JH may influence the mucopolysaccharide secretory function of the accessory cells, the activity of which seems to account for changes in electrical resistance and therefore in sensitivity of the labellar chemosensilla.