statementUsing a novel closed-loop behavioral assay, we show that Drosophila larvae can navigate light gradients exclusively using temporal cues. Analyzing and modeling their behavior in detail, we propose that larvae achieve this by accumulating luminance change during runs. AbstractNavigating across light gradients is essential for survival for many animals. However, we still have a poor understanding of the algorithms that underlie such behaviors. Here we develop a novel phototaxis assay for Drosophila larvae in which light intensity is always spatially uniform but constantly updates depending on the location of the animal in the arena. Even though larvae can only rely on temporal cues in this setup, we find that they are capable of finding preferred areas of low light intensity. Further detailed analysis of their behavior reveals that larvae initiate turns more frequently and that turn amplitudes become higher when animals experience luminance increments over extended periods of time. We suggest that temporal integration of luminance change during runs is an important -and so far largely unexplored -element of phototaxis.

Navigating across light gradients is essential for survival for many animals. However, we still have a poor understanding of the algorithms that underlie such behaviors. Here we develop a novel closed-loop phototaxis assay for Drosophila larvae in which light intensity is always spatially uniform but updates depending on the location of the animal in the arena. Even though larvae can only rely on temporal cues during runs, we find that they are capable of finding preferred areas of low light intensity. Further detailed analysis of their behavior reveals that larvae turn more frequently and that heading angle changes increase when they experience brightness increments over extended periods of time. We suggest that temporal integration of brightness change during runs is an important – and so far largely unexplored – element of phototaxis.