Trans-sexually grafted antennae alter pheromone-directed behaviour in a moth

Area of Science:

• Neuroethology
• Insect olfaction
• Behavioral neuroscience

Background:

• Male Manduca sexta exhibit pheromone-modulated anemotaxis for mate-seeking, mediated by male-specific antennal sensory neurons.
• These neurons project to pheromone-specific interneurons within the macroglomerular complex (a sexually dimorphic brain region).
• Normal females lack these male-specific neural circuits and behaviors.

Purpose of the Study:

• To investigate the neural basis of pheromone-guided anemotaxis in female Manduca sexta.
• To determine if the macroglomerular complex is essential for pheromone detection in females.
• To explore the potential for shared neural pathways in olfactory-guided behaviors.

Main Methods:

• Grafting male antennae onto female Manduca sexta to create gynandromorphs.
• Electrophysiological recordings from antennal lobe interneurons in response to pheromone stimulation.
• Behavioral assays in a wind tunnel to assess anemotaxis in response to pheromones and host plant odors.

Main Results:

• Gynandromorphic females with grafted male antennae responded to pheromone stimulation with anemotaxis.
• Interneurons in the antennal lobes of gynandromorphs showed postsynaptic responses to pheromone components and projected to a macroglomerular complex-like region.
• Normal females exhibited similar anemotaxis in response to tobacco plant odor, suggesting a common motor pathway.

Conclusions:

• The macroglomerular complex and associated interneurons are crucial for processing pheromone information and mediating anemotaxis in male moths.
• Gynandromorphic females demonstrate that the presence of male-specific olfactory circuits can confer pheromone-guided behaviors.
• A common motor pathway likely underlies both male pheromone-seeking and female host-plant-seeking behaviors, highlighting neural plasticity and convergence.