Fig. 3: Testing of Drosophila magnetic sensing in the gravity negative-geotaxis assay.

a, Schematic of the apparatus. A desktop computer (1), situated outside the shielded chamber, controlled the power supplies (2), the switching box (3) and the double-wrapped three-dimensional Merritt four-coil system (4). Large parts of the 12 coils have been omitted for visual clarity; a photograph of the chamber and coils can be found in ref. ²⁹. Tubes containing the flies (5) were placed in the centre of the coils. Temperature, light and magnetic field sensors (6) monitored the experiments continuously. These sensors were connected to a laptop (7) that also controlled the video camera (8). The flies were illuminated with UV-blue, blue or red light via an array of LEDs (9). A second LED array (10) generated infrared light for filming. b, Climbing behaviour of CS-LE flies under blue light (410–490 nm), showing the time dependence of the proportion of flies reaching 15 cm when exposed to a 300 µT magnetic field compared with sham exposure conditions with no applied magnetic field. Data are shown as mean (thick lines) and mean ± confidence interval (thin lines) for proportion data. Grey dashed line indicates the proportion of flies able to climb 15 cm in 15 s. c, Average height climbed by flies as a function of time (same conditions as b). Data are shown as mean (thick lines) and mean ± s.d. (thin lines). No significant difference between sham (0 μT) and exposed (300 µT) conditions was found. b,c, Data for 15 groups of ten flies in each condition (exposed and sham).