FIGURE 1.

Zebrafish larvae perform phototaxis and UV avoidance in a closed loop paradigm. (A) Closed loop apparatus used in this manuscript. The fish is monitored in real time at ∼100 fps using a camera. The larva swims freely in a petri dish arena illuminated with infrared light. As the animal swims, its movements are tracked in real time and stimuli are projected from the bottom, aligned to the animal. After each experiment, the larval movement is segmented into individual turn events that are condensed into a preference index reflecting the stimulus choice of the animal. (B) Modeled absorption spectra of the larval zebrafish cone pigments, including the beta band of absorption. (C) Emission spectra of the LEDs used to project stimuli in this manuscript. (D) Theoretical relative excitation each LED elicits on each cone. The colors correspond to the LED colors in (C). As mentioned, all cones are excited to an extent. (E) Larval turning direction preference indices for UV, blue and red stimuli against darkness. The stimuli are listed at the left side of each plot and preference index is expressed as the length of the horizontal bars (bars are mean ± SEM, N = 19 larvae from different clutches. Stars represent p-value < 0.05 in a paired bootstrap test comparing the lowest power level to the others). (F,G) average total displacement per bout (F) and duration of each bout (G) for each of the stimuli used above. Stimuli are indicated at the bottom with the color on each side represented vertically (points are mean ± SEM, fish are same as above).