S1-4.6 Jan. 5 Sensory Encoding in the Gyroscopic Halteres of the Crane Fly Holorusia FOX, J.L.*; MYHRVOLD, C.A.; DANIEL, T.L.; University of Washington; University of Washington; University of Washington email@example.com
Insect flight requires coordination of many sensory and motor circuits over several time scales. Since muscle activity must often be modulated at a rate faster than can be achieved by visual circuits, rapid mechanoreception is crucial. The most conspicuous examples of specialized mechanosensory organs are the halteres of Dipteran insects. Derived from hindwings, halteres are densely packed with mechanoreceptive sensillae at their bases and are known to act as gyroscopes in flight, during which they oscillate at the same frequency as the wings (approximately 28 Hz). Despite a long history of analysis of halteres and their importance as mechanoreceptors, the encoding properties of their afferent neurons have not been examined. To determine the sensory capabilities of these gyroscopic organs, we performed intracellular recordings of axons in the haltere nerve of the crane fly (Holorusia rubiginosa) while stimulating the haltere in a biologically relevant manner. We used high-speed videography of crane flies in free flight to examine the natural motions of the haltere and based our stimulus parameters on the angles and frequencies observed. We found that the haltere nerve contains neurons that can encode stimuli up to at least twice the natural frequency. Because the haltere neurons can encode oscillations at twice the wingbeat frequency, they have the capacity to capture and transmit information about Coriolis forces that occur during simultaneous oscillation and rotation of the haltere during flight. This capability of the haltere neurons indicates that they are an important component of Dipteran flight control. Our recording techniques, combined with our data about the natural motion of halteres during flight, will allow us to further examine the details of their function as gyroscopic mechanoreceptors.