Response profile of pheromone receptor neurons in male Grapholita molesta (Lepidoptera: Tortricidae)

Abstract

The response profile of olfactory receptor neurons (ORNs) of male Grapholita molesta (Busck) to the three female sex pheromone components [(Z)-8-dodecenyl acetate (Z8-12:Ac), (E)-8-dodecenyl acetate (E8-12:Ac), and (Z)-8-dodecenyl alcohol (Z8-12:OH)] was tested with single sensillum electrophysiology. Sensilla trichodea housed normally one, but sometimes two or three ORNs with distinct action potential amplitudes. One third of the sensilla contacted contained ORNs that were unresponsive to any of the pheromone components tested. The remaining sensilla contained one ORN that responded either to the major pheromone component, Z8-12:Ac ('Z-cells', 63.7% of sensilla), or to its isomer E8-12:Ac ('E-cells', 7.4% of sensilla). 31% of Z- and E-sensilla had I or 2 additional cells, but these did not respond to pheromone. None of the 176 sensilla contacted hosted ORNs that responded to Z8-12:OH. The proportion of Z- and E-cells on the antennae (100:11.6, respectively) is similar to the proportion of these compounds in the blend (100:6, respectively). The response of Z-cells was very specific, whereas E-cells also responded to the Z isomer, albeit with lower sensitivity.

BA was supported by a Ph.D. fellowship from MINECO Ministry of Spain, and CG by research Grant AGL2010-17486 from the same agency. C. David and J. Valls helped with the kinetic curves. M. Evenden, K.F. Haynes, and P. Lucas reviewed an earlier version of this manuscript.