Optimizing light environment for aquaculture: Balancing growth and physiological stress in clam Cyclina sinensis under different light intensities

Although light intensity is an important environmental factor for aquatic animals, its effects on digestive, immune, and antioxidant physiology in bivalves remain poorly understood. In this study, Cyclina sinensis was exposed to four light intensities (0, 400, 4000, and 12000 lx) for 60 days, and samples were collected at day 30 and day 60 to determine growth performance, digestive, immune-antioxidant enzyme activities, and related gene expression. The results showed that: (1) Growth performance, represented by the specific growth rate (SGR), was significantly highest at 12000 lx at both sampling time points. (2) Pepsin and cellulase activities peaked at 12000 lx, while amylase decreased gradually as light intensity increased and maintained significantly higher activity at 0 and 400 lx on both time points. (3) On day 30, 12000 lx increased AKP and ACP activities as well as MDA content. 0 lx and 400 lx maintained high SOD and CAT activities and low MDA content. On day 60, SOD activity decreased with increasing light intensity, 0 lx showed the lowest MDA content but inhibited ACP activity. The expression levels of HSP27 , HSP90 and GSTP1 overall increased with rising light intensity and reached maximum at 12000 lx on day 60. LYZ expression was consistently elevated in 0 lx at both time points, while IL-17–3 expression reached the maximum at 12000 lx on day 30 and 0 lx on day 60. In conclusion, 12000 lx light intensity significantly promoted growth and digestive efficiency in C. sinensis but induced oxidative stress.