Figure 2.

Zebrafish larvae respond to paramecia with eye convergence during hunting. (A) Individual frames from a movie sequence of a typical hunting episode showing the 4 stages at which we quantified eye position. The paramecium is indicated by an orange arrowhead. In this case, a J-turn occurs concurrently with eye convergence when the larva first responds to the paramecium. (B) Eye vergence angle (mean ± s.e.m.) at four stages in the hunting routine. (C) Change in right and left eye positions from the start of the hunting episode (green symbols) to the pre-capture frame (brown symbols). Note that nasal rotations correspond to a numerical increase in left eye position and a numerical decrease in right eye position. (D) Change in eye position (start → pre-capture) versus starting eye position for the left (blue) and right (red) eyes. Note that right eye positions were inverted (multiplied by −1) in this plot to aid comparison between the eyes. (E) Cumulative tail angle at the peak of the first J-bend in 62 trials (33 right (yellow) and 29 left (green) J-bends) where larvae first responded to the paramecium with a J-turn in addition to eye convergence. Cumulative angle is plotted as 8 values from the anterior to posterior end of the tail. Thick lines with symbols show mean tail angle profiles. (F) Schematics showing model tails reconstructed from the mean tail angle profiles in (B). The eyes are also depicted at the mean vergence angle 62.5 ms after larvae respond to their prey. (G) Distribution of distances between the center of the fish’s head and the paramecium when the larva first responds to prey. (H) Distribution of angular locations of the paramecia, measured from the extended midsaggital axis of the fish, when the larva first responds to prey. Left panel shows data for all responses and center and right panels show data segregated according to whether the first orienting response included a J-turn or not.