Active and passive antennal movements during visually guided steering in flying drosophila

Abstract

Insects use feedback from a variety of sensory modalities, including mechanoreceptors on their antennae, to stabilize the direction and speed of flight. Like all arthropod appendages, antennae not only supply sensory information but may also be actively positioned by control muscles. However, howflying insects move their antennae during active turns and howsuch movements mightinfluence steering responses are currently unknown. Here we examined the antennal movements of flying Drosophila during visually induced turns in a tethered flight arena.In responsetoboth rotational and translational patterns ofvisual motion,Drosophilaactively moved their antennae inadirection oppositetothatof the visual motion.Wealso observed two typesofpassive antennal movements: small tonic deflections of the antenna and rapid oscillations at wing beat frequency. These passive movements are likely the result of wing-induced airflow and increasedin magnitude when the angular distance between the wing and the antenna decreased.In response to rotational visual motion, increases in passive antennal movements appear to trigger a reflex that reduces the stroke amplitude of the contralateral wing, thereby enhancingthevisuallyinducedturn.Althoughtheactive antennalmovements significantlyincreasedantennaloscillationbybringingthe arista closer to the wings, it did not significantly affect the turning response in our head-fixed, tethered flies. These results are consistent with the hypothesis that flying Drosophila use mechanosensory feedback to detect changes in the wing induced airflow during visually induced turns and that this feedback plays a role in regulating the magnitude of steering responses. © 2011 the authors.