Effects of yellow light intensity on growth, feeding, digestion, antioxidant capacity, and nutritional composition in juvenile razor clam Sinonovacula constricta

The razor clam Sinonovacula constricta , a commercially and nutritionally important bivalve, thrives optimally under yellow light. Herein, we investigated how varying yellow light intensities (0, 10, 20, and 40 μmol/m 2 /s) affect growth, physiology, and nutritional quality of juveniles (shell length: 2.62 ± 0.29 mm). After two weeks, clams exposed to 10 and 20 μmol/m 2 /s exhibited superior growth and feeding rates compared to those at 0 and 40 μmol/m 2 /s. Digestive enzyme assays revealed declining α -amylase activity with increasing light intensity, while pepsin activity peaked at 10 μmol/m 2 /s; lipase and trypsin activities remained unaffected. These findings suggest enhanced digestion underpins improved growth at lower light intensities. Oxidative stress responses showed elevated SOD, CAT, and GPx activities at 0–10 μmol/m 2 /s, a sharp decline at 20 μmol/m 2 /s, and partial recovery at 40 μmol/m 2 /s. Conversely, MDA levels rose progressively with light intensity. Gene expression analysis revealed that sod peaked at 40 μmol/m 2 /s, while cat and gpx were higher at 0 and 40 μmol/m 2 /s. These results indicate oxidative damage at 20 μmol/m 2 /s and overwhelmed defenses at 40 μmol/m 2 /s. Besides, glycolysis genes (except pyruvate kinase) peaked at 40 μmol/m 2 /s, lipid synthesis genes favored lower intensities, and tryptophan metabolism gene declined with increasing light intensity except at 40 μmol/m 2 /s. Consequently, juveniles cultured under 10 μmol/m 2 /s accumulated higher carbohydrate, lipid, and protein content, alongside elevated polyunsaturated fatty acids (e.g., 18:4n-3, 22:6n-3). Collectively, low yellow light intensity (10 μmol/m 2 /s) promotes growth, mitigates physiological stress, and enhances nutritional value in S. constricta , providing practical insights for optimizing aquaculture productivity and welfare. • Juvenile S. constricta showed the best growth at 10–20 μmol/m 2 /s. • Juveniles reared at 10–20 μmol/m 2 /s exhibited a better feeding rate and digestion. • Juveniles reared at 10–20 μmol/m 2 /s exhibited enhanced antioxidant capability. • Juveniles reared at 10–20 μmol/m 2 /s experienced less stress. • Juveniles reared at 10–20 μmol/m 2 /s exhibited improved nutritional quality.