Meeting Abstract
The compound eyes of Drosophila express five rhodopsins, each with a distinct sensitivity to the wavelength of light, providing a sensory basis for color vision. What the flies use their color vision for is not well understood because few spontaneous color behaviors have been described. To address this shortfall, we have investigated how color vision influences their flight control. We developed a novel ultraviolet (UV) and green projector system to display wide-field visual stimuli and measured the flight responses of tethered flies by optically recording changes in wing stroke amplitude. First, we found that flies can track the motion of an object, a vertical UV stripe on a green background, regardless of the color intensities used, even when the UV and green intensities are matched so that they provide no luminance contrast. This is achieved because the ON- and OFF-motion pathways have different points of isoluminance: when the UV intensity is matched to the green intensity for OFF-motion, it is still visible for ON-motion, and vice versa. Second, flies stabilize an isoluminant horizon using a rapid phototaxic response to large areas of UV illumination, and this phototaxis has a wavelength tuning distinct from that of ON- and OFF-motion. Third, the steering responses to looms depend on the color of the loom and the background, consistent with the wavelength tuning of the ON- and OFF-motion pathways: they are colorblind for green looms against a UV background, but preserved for UV looms against a green background. Finally, when presented with a uniform scene, the wing beat frequency varies with the intensity of UV and not green light. Our results show how the wavelength of light can influence multiple aspects of flight attitude and control, and allow the operation of color vision circuitry to be investigated in the context of natural behaviors.
