Effects of light on growth, feeding rate, digestion, and antioxidation in juvenile razor clams Sinonovacula constricta

Abstract

In the present study, we explored the effects of seven light treatments (white, violet, blue, cyan, green, yellow, and red) on juvenile Sinonovacula constricta (length, 693.79 ± 82.91 μm), employing dark treatment as a control. A rearing experiment was conducted for one week in which the feeding rate was examined daily, e.g., one, two and three h after feeding. At the conclusion of the experiment, overall growth was calculated, and enzymatic activity related to digestion, superoxide dismutase, catalase, and glutathione peroxidase pertaining to antioxidant biomarkers, as well as expression levels of genes related to antioxidation and stress response, were examined. The results showed that the highest growth rates were observed in the yellow light group, while the lowest growth rates were found in the violet and blue light groups; on the other hand, no significant differences were found among the other groups. Meanwhile, when exposed to white, yellow, or green light, juveniles exhibited high feeding rates, while those in the violet and blue light groups showed low feeding rates. Regarding enzymatic activity related to digestion, those of α-amylase, lipase, pepsin, and trypsin were relatively higher in the yellow light group than in the other groups. Regarding oxidative stress, the yellow light group showed higher superoxide dismutase, catalase, and glutathione peroxidase activities than the other groups. In contrast, the lowest malonaldehyde level was found in the white light group, followed by yellow light, while there were no significant differences among the other groups. In addition, the expression levels of genes related to antioxidation and stress response (heat shock protein 70 and glucose-regulated protein 78) in juveniles generally exhibited higher levels in the red light group, whereas they showed relatively lower levels in the yellow light group. Collectively, these results suggest that the application of yellow light may facilitate the growth of juvenile S. constricta, while red and violet light have opposite effects.