Fig 9. Visually mediated behaviour is reduced following ablation of UV or blue cones but recovers rapidly following blue cone ablation.

Thus the recovery of visually mediated behaviour has a time course that depends on the type of cone photoreceptor ablated. Ablation of UV or Blue cones leads to the immediate impairment of visual function (panels A & B, respectively; the first triplet of histograms in each shows behaviour severely decreased following cone ablation (red bars) compared to controls (grey bars)). Visually mediated behaviour regenerated following UV cone ablation over the course of several days (A). Unexpectedly, vision is rapidly restored following ablation of blue cones (B; e.g. red bar at 24 hours since the end of drug treatment). We designed and empirically optimized a visually evoked behaviour based on the optomotor response (OMR; Figs 8A and S1) that stimulates a quantifiable directional movement of freely swimming larval zebrafish. “WT MTZ” are wild type zebrafish receiving the prodrug metronidazole (MTZ) as a control treatment, presented in dark grey bars; “UV DMSO” or “Blue DMSO” in light grey bars are a second control, representing transgenic fish that express nitroreductase for ablation of UV or blue cones, respectively, and these fish received vehicle control (DMSO) only; “UV MTZ” or “Blue MTZ” in red bars are transgenic fish treated with prodrug MTZ and thus had their UV or Blue cones ablated, respectively, immediately prior to testing of visual ability at time zero. Sample sizes (n = number of larvae tested) are reported at the bottom of each bar, and are detailed in Table 2. Table 2 also reports the data prior to the normalization used to generate this Figure. ***p<0.001 experimental relative to controls, *p<0.05 experimental compared to the wild-type control. The visually mediated OMR behaviour had significantly recovered to be indistinguishable from controls 72 hours after UV cone ablation (A), and 24 hours following blue cone ablation (B).