Summary
We provide evidence for spontaneous quadramodal magnetic orientation in a larval insect. Second instar Berlin, Canton-S, and Oregon-R X Canton-S strains of Drosophila melanogaster exhibited quadramodal orientation with clusters of bearings along the four anti-cardinal compass directions (i.e. 45°, 135°, 225°, 315°). In double-blind experiments, Canton-S Drosophila larvae exhibited quadramodal orientation in the presence of an earth-strength magnetic field, while this response was abolished when the horizontal component of the magnetic field was cancelled, indicating that the quadramodal behavior is dependent on magnetic cues, and may reflect properties of the underlying magnetoreception mechanism. In addition, a reanalysis of data from studies of learned magnetic compass orientation by adult Drosophila melanogaster and C57BL/6 mice reveals patterns of response similar to those exhibited by larval flies suggesting that a common magnetoreception mechanism(s) may underlie these behaviors. Therefore, characterizing the mechanism(s) of magnetoreception in flies may hold the key to understanding the magnetic sense in a wide array of terrestrial organisms.
