Presence of Long-Lasting Peripheral Adaptation in Oblique-Banded Leafroller, Choristoneura rosaceana and Absence of Such Adaptation in Redbanded Leafroller, Argyrotaenia velutinana
Pre-exposure of male oblique-banded leafrollers, Choristoneura rosaceana (Harris), to the main component of their pheromone blend and traces of its geometric isomer (Z11–14:Ac and E11–14:Ac, respectively) at 36 ± 12 ng/ml air for durations of 15 and 60 min in sealed Teflon chambers with continuous air exchange significantly reduced peripheral sensory responses to these compounds as measured by electroantennograms (EAGs). The EAG responses of C. rosaceana to all tested dosages of pheromonal stimuli and blank controls were lowered by 55–58% and made a linear recovery to 70–100% of the pre-exposure amplitude within 12.5 min at a rate of 3–4 %/min. Exposures of 5 min were insufficient to maximally adapt C. rosaceana; however, exposures of 15 and 60 min reduced sensory responsiveness to the same minimum. In contrast, EAG responses of redbanded leafroller, Argyrotaenia velutinana (Walker), after identical pheromone exposure for 5 and 60 min yielded no long-lasting peripheral sensory adaptation as measured by EAGs, even though this species shares the same main pheromone components with C. rosaceana. We postulate that the long-lasting peripheral adaptation observed for C. rosaceana is a mechanism that impedes central nervous system habituation in this species. In contrast, A. velutinana may be more susceptible to central nervous system habituation because it lacks the capacity for minutes-long adaptation. We propose that long-lasting adaptation may be a mechanism explaining some of the variation in efficacy of pheromone-based mating disruption across taxa.