Effects of light intensity on the growth, non-specific immunity, and ovarian development of juvenile ridgetail white prawn (Exopalaemon carinicauda)

Abstract

Light intensity is a critical environmental factor in aquaculture, profoundly influencing aquatic species’ growth and reproductive performance. This study investigated the effects of five light intensities (0, 100, 350, 600, and 1600 lx) on growth performance, non-specific immunity, ovarian development, and biochemical analysis of juvenile female ridgetail white prawn (Exopalaemon carinicauda, body length 5.16 ± 0.02 cm and wet weight 1.96 ± 0.01 g) under a 12L:12D photoperiod for 30 days, using natural light (0–1600 lx) as a control. Growth parameters including final wet weight (Wt), weight gain rate (WGR), specific growth rate (SGR), and survival rate (SR) exhibited a unimodal response, peaking at 100 lx (2.66 ± 0.03 g, 70.58 ± 2.09%, 1.03 ± 0.02%, and 57.78 ± 1.92%, respectively). Digestive enzyme activities including Chymotrypsin, α-amylase (α-AMS), and lipase (LPS) increased with light intensity, reaching maximum levels at 1600 lx (12.23 ± 0.51 U/mg prot, 24.36 ± 0.86 U/mg prot, and 5.29 ± 0.48 U/mg prot, respectively). In contrast, key non-specific immune enzymes, superoxide dismutase (SOD) and alkaline phosphatase (AKP), displayed optimal activity at 100 lx (12.95 ± 0.96 U/mg prot and 109.66 ± 12.31 U/mg prot, respectively). Ovarian development indices revealed an inverse trend between hepatosomatic index (HSI) and gonadosomatic index (GSI), with GSI peaking at 100 lx (4.59 ± 0.05%) and HSI at 1600 lx (3.60 ± 0.05%). Biochemical analysis demonstrated significantly higher total cholesterol (TC), triglycerides (TG), and vitellogenin (Vg), and estradiol (E2) levels at 100 lx (0.86 ± 0.04 mmol/g prot, 0.08 ± 0.01 mmol/g prot, 17.73 ± 0.37 µg/mL, and 52.09 ± 2.75 ng/L, respectively) (P < 0.05). Ovarian nutrient accumulation (22.60% of protein, 25.37% of lipid, and 0.04% of glycogen) was maximized at 100 lx, significantly surpassing hepatopancreatic reserves (P < 0.05). These findings indicate that 100 lx is the optimal light intensity for promoting growth, enhancing ovarian development, and optimizing nutrient accumulation in female E. carinicauda, providing valuable insights for crustacean reproductive management.