Responses of olfactory receptor neurons in Utetheisa ornatrix to gender-specific odors

We recorded the electrophysiological responses of individual olfactory rece ptor neurons in sensilla trichodea on the antennae of adult arctiid moths, Utetheisa ornatrix, to stimulation with volatiles associated with both sexe s. All trichoid sensilla contain at least two receptor neurons, each with d istinct action potential amplitudes and waveforms, that respond dichotomous ly to male and female odors. Although, neither female neuron responds to ex tracts of coremata or the male-produced pheromone hydroxydanaidal, they do respond in a gender-specific manner to the volatiles emanating from whole p upae, hemolymph, thoracic froth, and adult animals of several ages. Thoraci c froth, which contains pyrrolizidine alkaloids, is thought to play a role in defense. Froth from moths reared on diets, with or without added pyrroli zidine alkaloids, were equally effective in eliciting gender-specific patte rns of response. Male trichoid receptor neurons respond to these same mater ials with similar patterns of activation. These receptor neurons provide in formation about substances, which we have termed "gender odors," that are p ersistently emitted by nearby animals. These substances do not appear to be the same as those already known to be involved in defense or the sexual di alog between individuals.