VARIATIONS IN SALT SENSITIVITY RELATED TO TYPE AND POSITION OF LABELLAR CHEMOSENSILLA IN PROTOPHORMIA-TERRAENOVAE

Electrophysiological responses to NaCl in the concentration range 1-1000 mM were obtained from each of the 11 intermediate and 13 large labellar chemosensilla in the blowfly Protophormia terraenovae. Up to three of the four chemoreceptor cells associated with each chemosensillum responded to NaCl in both sensillum types; the spike discharges of two of these cells were analysed and cross-compared. Differences in chemoreceptor sensitivity and response pattern resulted between intermediate and large sensilla. Sensitivity differences were found, by means of the cluster analysis, within each sensillum type in relation to sensillar topology and are discussed in the light of a possible spatial contribution to the sensory coding process.