Effects of different light intensity on growth, feeding, retinal structure and expression of vision-related genes of silver pomfret

The intensity of light has been known to play a crucial role in the growth and developmental processes of fish through the visual system. To investigate effects of light intensity on the growth, feeding patterns, retinal structure, and vision-related genes of silver pomfret, we set four groups including control (natural light), L0 (darkness), L100 (100 lux), and L1000 (1000 lux) at larval, juvenile and young stages. Full length and survival rate were significantly lower in L0 at larval and juvenile, while feeding rate was significantly higher in control and L1000; at young stage, weight and feeding rate was significantly lower in L0 and specific growth rate was significantly higher in control; but there was no significant difference in condition factor among four groups. Next, at larvae stage, we observed a clear ten-layer structure of the retina, which developed better in high light intensity groups; the number of melanin particles in pigment epithelial layer also increased with development of retina; at juvenile and young stages, low light intensity led to aggregation of melanin particles, and thickness of ganglion cell layer became thinner, with cell body decreasing to one layer in high light intensity groups. Finally, we examined expression of seven vision-related genes: RH1 gene was up-regulated at larvae stage and down-regulated at juvenile and young stages in L0 and L100, and RH2 and LWS initially increased and then declined with the development of the fish in control; conversely, SWS, SWS2, RPE65, and RBP were up-regulated in high light intensity groups. In conclusion, our study suggests that high light intensity can lead to improved growth and feeding patterns in fish, as well as promoting the development of retina and up-regulating the expression of pigment genes. Consequently, our findings provide a valuable theoretical foundation for optimizing the lighting scheme of the artificial breeding process of silver pomfret.