Photoreception of UV light is reduced following ablation of UV cones as measured by changes in body pigmentation.

<p>UV cones were ablated in larvae, and larval body pigmentation was measured in response to UV light; zebrafish larvae of this age are known to darken in response to UV light via melanin dispersion. <b>A.</b> Dorsal view of larval zebrafish. Binarization of images was used to quantify melanosome reaction to UV light. Larvae were imaged at multiple time points, beginning with dark-adapted larvae. <b>B.</b> The number of pixels in dark-adapted larvae was given a melanin index of 1. <b>C.</b> UV light exposure causes wild type fish to darken, increasing the melanin index. <b>D.</b> Shortly after drug treatment (0 hours), control larvae respond to UV light with the expected darkening of body pigmentation (grey lines), whereas larvae with UV cones ablated exhibit a significantly delayed response (red line). <b>E.</b> Larvae tested 24h after drug treatment reveal that UV cone ablation significantly impairs photoreception. <b>F,G.</b> Larvae tested 48 and 72 hours after drug treatment reveal a gradual recovery of sensitivity to UV light to levels indistinguishable from controls. ** = p<0.01 compared to UV+DMSO group *** = p<0.001 comparing UV+MTZ group to larvae in all control groups in the same timepoint, and these data are also significantly different (p<0.01) from the melanin index of the same UV+MTZ larvae in the dark-adapted state. Statistical significance was determined by Two-way ANOVA with a post-hoc Tukey test. The standard error surrounding each mean is reported in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0166932#pone.0166932.t003" target="_blank">Table 3</a>.