DIEUDONNE, A.; SANE, S.P.; Univ. Of Washington, Seattle; Univ. Of Washington, Seattle: The encoding properties of antennal mechanosensors in the hawk moth, Manduca sexta

During locomotion, insects rely on their antennae for a wide variety of sensory stimuli. In addition to being the primary olfactory organs, the antennae also serve a very important mechanosensory role mediated by sensory neurons located in the two basal antennal segments, the scape and the pedicel. During flight, the antenna undergoes a low frequency motion due to wind gusts as well as high frequency vibration due to wing flapping. This motion causes a passive movement of the distal multi-annular flagellar segment and thus a deformation in the scape-pedicel joint. This deformation is encoded by a set of mechanosensory cells called Johnston’s organs spanning the scape-pedicel joint and by superficial bristle organs called the Bohm’s bristles on the surface of the antenna. To study how these sensors encode mechanosensory information in the hawk moth Manduca sexta, we provided controlled mechanical stimuli varying in frequency and amplitude to the flagellum and recorded their intracellular sensory response from the antennal nerve. After recording, these neurons were injected with a fluorescent dye to image their innervation pattern. The mechanosensory neurons showed both phasic and tonic firing activity in response to step or sinusoidal mechanical stimuli, suggesting that the neurons may encode information about the position and motion of the antenna. Further, the neuroanatomical data suggest that the axons terminate in a region of the brain that also contains dendrites from antenno-motor neurons. This work was supported by an Office of Naval Research grant to Thomas L. Daniel.