Handedness in Drosophila locomotor behavior. Sean M. Buchanan, Benjamin L. de Bivort. The Rowland Institute at Harvard, Cambridge, MA.
Genetically identical individuals can display variability in their gene expression, morphology and behaviors, but the biological significance of this variation has only recently begun to be appreciated. We have investigated whether Drosophila melanogaster display individual variation in locomotor behaviors. We find that, during walking, individual flies exhibit bias in left-right turning, with some flies being strongly left-handed or right-handed. The distribution of turning scores is much broader than would be expected by chance and an individual flys handedness is persistent over its lifetime. Furthermore, this idiosyncratic bias is non-heritable and cannot be explained by gross morphological variation. Surprisingly, we find that locomotor handedness is influenced by vision; when walking in darkness, flies exhibit a narrower distribution of turning biases. This suggests that individual handedness may be under neural control and we have examined the roles that neural circuits within the central complex play in left-right turning. The ring neurons of the ellipsoid body have been implicated in the integration of sensory inputs and locomotion. We find that silencing these neurons reduces variation in handedness, similar to the effect of eliminating visual stimuli during walking. We are currently investigating whether handedness is caused by individual asymmetry in these integration neurons.