Meeting Abstract
The fruit fly, Drosophila melanogaster, flies across vast distances by means of a navigation system which is visually guided by celestial cues. As a non-diapausing insect, we wanted to shed light on how Drosophila might arrive at seasonally inhospitable habitats, such as the Mojave Desert, by testing whether seasonal temperature and light conditions affect Drosophila flight headings. We reared wildtype Drosophila melanogaster under divergent daylength and temperature conditions to simulate summer, winter and spring. After reaching adulthood, flies were tethered and placed in a flight simulator, which surrounds the fly with a visual panorama in which we displayed a simulated sun (bright spot) or a landing site (dark, vertical stripe). A machine-vision software tracked the fly’s wing strokes, allowing the fly to control the azimuthal angular velocity of the stimulus. An analysis of flight headings suggests that flies reared under winter conditions tend to fixate the sun frontally, thus performing phototaxis, whereas summer and spring flies adopt a wider range of non-frontal headings, ie. menotaxis. Seasonal variations in flight heading were observed within a single generation, which led us to investigate whether other physical characteristics — wet mass and pigmentation — vary plastically. We found significant variation in wet mass between the seasonal treatments, with winter females weighing less and males weighing more than their spring and summer counterparts. Comparing the reflectance percentage of abdomen and thorax pigmentation, we found significantly darker regions on the winter flies. In conclusion, our data lends support to the hypothesis that seasonal developmental conditions can affect navigation strategy and physiology.
