Figure 1. Sensory experience corresponding to unconstrained chemotactic behavior.
(A) Illustrative trajectory of a larva freely moving in an attractive odor gradient (isoamyl acetate, source concentration: 0.25 M). Position of the midpoint shown in black; position of the head shown in magenta. Two run segments, R1 and R2, are underlined in green. Turns are depicted as white disks. White arrows indicate the direction of motion. (B) Reconstruction of the odor gradient based on numerical simulations of the odor diffusion process modeled by a partial differential equation (PDE) system with realistic boundary conditions (‘Materials and methods’). The gradient shown in panel A corresponds to a snapshot obtained 60 s after onset of the odor diffusion. (C) Time course of the odor concentration experienced at the head (magenta) and midpoint (black) of the larva during the trajectory shown in panel A. The sensory experiences are reconstructed based on mapping the positions of interest on the dynamic odor gradient computed upon integration of the PDE system for the entire duration of the trajectory. The green box outlines the sensory experience corresponding to run segments R1 and R2. Small disks on the abscissa indicate the turns comprised in this behavioral sequence.