The roles of blur and eye convergence in distance estimation in larval zebrafish.

Animals use an array of visual cues to gauge distance, and their underlying neural mechanisms remain largely unknown. Zebrafish larvae execute different hunting behaviors depending on distance to the prey, providing a simple model system in which to study this process. To identify distance cues, we presented equivalent prey stimuli at increasing distance and recorded hunting behaviors. We found that the initial convergence angle was lower for more distant prey, suggesting that they are able to gauge distance to the prey via monocular cues. We investigated blur as a possible monocular cue, and found that by artificially blurring the stimulus, we were able to reduce initial convergence and strike probability. This implicates blur as a distance cue in zebrafish prey capture, adds to our knowledge of how larvae are able to visually target and accurately capture prey.