Light-dependent conversion of body color change pattern during zebrafish development

Light exposure during zebrafish development converts the body color change pattern between 2 dpf and 5 dpf, with a 14-h pulse on 3 or 4 dpf sufficient to trigger it.

• Why it matters: The developmental switch in light-responsive body color is known to differ between 2 dpf and 5 dpf, but the light dependence and underlying regulatory control were unclear.
• What they did: Larval Danio rerio were reared in darkness or light, and a 14-h light exposure at 3 or 4 dpf was tested; conversion persisted after ablation of most exorh-expressing pineal photoreceptor cells, while pmch/pmchl transcription was measured.
• The result: Dark-reared larvae showed light-induced darkening like 2-dpf, and converted 3-L and 4-L larvae did not differ in pmch/pmchl from dark-reared larvae, implying maturation is light-dependent and not explained by reduced pmch/pmchl alone.

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