Abstract
With its small size and limited motor tool set, the Drosophila larva is a good system to study how animals alter specific elements of their behavior to search and reach optimal environmental conditions. We aim to understand the larva’s response to temperature across development, in sensory gradients, and to distinguish behavioral modulations based on physical changes from those due to sensory input. PID-controlled instruments drive temporal or spatial temperature gradients; combined with a moat system to replenish gels at high temperature, we can explore the larva’s full behavioral profile. Many larvae are simultaneously observed during free navigation in three different experiment types: temperature constant in time and space, constant in time but varying in space, or constant in space but varying in time. Computer vision software segments individual trajectories into an alternating sequence of runs and turns, analogous to a classic 2D random walk, and overall behavior is quantified into several metrics. Our results suggest that, between different constant temperatures, larvae modulate their turning rate but maintain turning size. Experiments involving temperature-insensitive mutants investigate how sensory decisions and physical changes separately affect behavior.