6.6 Wednesday, Jan. 4 Female pheromones modulate muscle activation patterns for pre-flight warm-up in male moths CRESPO, J. G.*; VCIKERS, N. J.; GOLLER, F.; University of Utah, Salt Lake City, Utah firstname.lastname@example.org
In Helicoverpa zea, the pheromone-mediated upwind flight of males is elicited by a two-component pheromone blend. Efficient upwind locomotion may require that moths warm up their endothermic flight muscles by shivering before engaging in flight. Previously, we showed that male H. zea sensing the attractive pheromone blend warmed up at a faster rate than males that were not exposed to this stimulus. We now investigated how heating rate is modulated. Possible mechanisms for increasing heat production include recruitment of additional motor units, increasing the rate of muscle contraction and reducing the mechanical movement by more simultaneous contraction of the antagonistic flight muscles. To test which mechanisms are used, we compared electromyographic recordings of the main flight muscles (i.e. the wing depressors or dorsal longitudinal muscles and the wing elevators or dorsal ventral muscles) of males exposed to the attractive pheromone blend with those of males not exposed to the odor. In addition, we simultaneously recorded the thoracic temperature and wing movements of these moths. Results indicate that the main mechanism for increasing heat production is the recruitment of additional motor units in both antagonistic flight muscles. Interestingly, the activation rate of monitored motor units did not change substantially, perhaps indicating that activation rate is not modulated and may be adjusted to the muscle contraction rate that is possible at any given thoracic temperature. Thus, sensing the pheromone induces males to recruit more motor units for achieving a higher heating rate. Supported by NSF grant IOB-0416861 to NJV and NSF DDIG grant IOS-1110836 to JGC.