Responses of three antennal specialist neurons of male Trichoplusia ni (Hübner) to sex pheromone components at and above naturally emitted levels

Abstract

Three types of sensilla on the antenna of Trichoplusia ni (Hübner) each house an olfactory receptor neuron that responds predominantly to only one component of the virgin female volatile effluvium. The HS(a) neuron responds to Z7-12:Ac at concentrations above 1 × 10 −15 M; the LS(b) neuron to Z7-14:Ac concentrations above 1 × 10 −15 M; the NS(a) neuron to Z9-14:Ac concentrations above 1 × 10 −18M. The sensitivity and selectivity of each of these neurons to all of the other compounds in the volatile female effluvium was investigated at various concentrations. At concentrations that correspond with those found downwind of a virgin “calling” female each of these neurons was highly selective for only one compound. Each responded to all of the other compounds at concentrations that exceeded the normal emission level of the female. The pheromone receptor neurons of the cabbage looper are, therefore, concentration-tuned specialists. Assays of various mixtures and the volatile emission of an excised female sex pheromone gland show that the response of the HS(a) specialist neuron reflects only the concentration of Z7-12:Ac, supporting a hypothesis that there is no mixture interaction with the other compounds within the female effluvium.