Effects of photoperiod on growth, digestive, metabolic and non-special immunity enzymes of Takifugu rubripes larvae

Abstract Photoperiod is one of the important environmental factors, which have important effects on the early growth and development, survival, metabolism and immune system of larvae. In the present study, Takifugu rubripes larvae were exposed to four different LED photoperiods: 8 L:16D, 16 L:8D, 20 L:4D and 24 L:0D from −1 to 30 days post hatching (DPH). We measured growth, activity of pepsin (PPS), lipase (LPS), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and non-specific immune enzyme activity of alkaline phosphatase (AKP), and acid phosphate (ACP), superoxide dismutase (SOD), Catalase (CAT), glutathione peroxide (GSH-PX), total antioxidant capacity (T-AOC) at 1, 5, 10, 15, 20, and 30 DPH. The results showed that there was no difference in the effects of photoperiod on the growth within 18 DHP, while 20 L:4D had a positive effect on the growth of the larvae after 19 DPH. The effect of photoperiod on digestive enzymes did not show obvious regularity. Compared with photoperiod, the changes of some digestive and metabolic enzymes were mainly affected by exogenous food (LPS, ALT, AST changed obviously after feeding Artemia). On the 30 DPH, the AKP of 8 L: 16D and 24 L: 0D groups was significantly higher than that of the other two groups, which indicated that 8 L: 16D and 24 L: 0D lighting might cause stress to fish body and lead to the increase of AKP. GSH-PX in newly hatched fish at 24 L:0D was significantly higher than that in other groups. Photoperiod had no significant effect on the enzyme activity of PPS, LDH, ACP, CAT and no obvious pattern was found. Overall, our results suggested that 20 L:4D promoted larval growth after 19 DPH and shorter photoperiods can be used to save electricity before 18 DPH of Takifugu rubripes larva.