Effects of light levels on retinal development in Danio rerio

Laboratory experiments examined the effects of different rearing light conditions on the development of the zebrafish retina. Larvae were raised in either total light, ambient (14h light/10h dark), or total dark conditions for 24h, 36h, 98h, 8d, or 15d. Larvae were then sacrificed, externally staged, and notochord length (NL) and eye diameter (ED) measured. Five larvae/age/treatment were cryostat-sectioned to determine eye structure and retinal thickness. Differences in larval growth and retinal structure were observed across treatments at all experimental ages tested. NL and ED measurements indicate that fish reared in the total dark treatment prior to 99hpf were developmentally delayed, compared to ambient, while those reared in the total light treatment were developmentally advanced. However, significant differences in retinal thickness and retina:eye width ratio were identified in larvae ≥99hpf. These findings suggest that rearing light level effects overall development during early embryogenesis and retinal development later, after 4--8dpf.