Cold avoidance and cold sensing in the Drosophila larva. Mason Klein^1,2, Ashley Vonner^1,3, Marc Gershow^1,2, Elizabeth Kane^1,3, Bruno Afonso¹, Paul Garrity⁴, Aravinthan Samuel^1,2. 1) Center for Brain Science, Harvard University, Cambridge, MA; 2) Department of Physics, Harvard University, Cambridge, MA; 3) Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, MA; 4) Department of Biology, Brandeis University, Waltham, MA.

   Response to temperature to reach environmental conditions conducive to survival and prosperity is a universally important behavior in all animals. Using the Drosophila larva as a model system, we connect the activity of cold sensing neurons to behavioral cold response. In particular, we identify a previously uncharacterized group of neurons with a unique morphology in each dorsal organ ganglion (DOG) that respond specifically to cooling. We map projections of these cold sensing neurons to the larval antennal lobe (LAL), where they innervate a region distinct from that of the olfactory receptor neurons also found in the DOG. We use in vivo 3D confocal imaging to monitor calcium activity while modulating temperature. The sensitivity to cooling and activation thresholds of these neurons are consistent with quantitative analysis of larval navigation on linear spatial temperature gradients, where crawling larvae also respond specifically to cooling. Further, laser ablation of the antennal nerve connecting the DOG to the central brain demonstrates that DOG neurons are required for cold avoidance behavior. These results point toward a more complete neuronal circuit understanding of temperature sensorimotor transformation in the larva with potential applications to higher organisms.