The effects of live food enrichment with various zinc and manganese sources on the antioxidant activity and osteogenesis-related gene expression in Arabian yellowfin seabream (Acanthopagrus arabicus) larvae

Abstract A 42-day larviculture trial evaluated Zn and Mn enrichment of live food (rotifers, Artemia nauplii, microalgae) on Acanthopagrus arabicus ( A. arabicus ) larvae. Enrichment sources were Zn Mn nanoparticles (TN), organic Zn Mn (TO), inorganic Zn Mn (TI), or TA (inorganic Zn Mn via Nannochloropsis oculata ), versus a Control (non-enriched). All diets were supplemented with 100 mg/L Zn and 240 mg/L Mn. Larvae with an average initial weight of 0.0280 mg were reared in fifteen 300-L tanks (5,000/tank) at 23.0 ± 1.0 °C and 42.0 ± 0.5 g/L salinity. Rotifers were provided from 2 to 21-days post-hatch (DPH) at 15 individuals/mL, followed by Artemia metanauplii from 18 to 42 DPH at 0.5-2 individuals/mL. Larval samples were collected at 0, 3, 7, 10, 15, 22, 30, 37, and 42 DPH to evaluate treatment effects. At 42 DPH, larvae in the TA and TO groups showed significantly greater wet weight (282.2 and 284.6 mg, respectively) and total length (23.8 and 23.9 mm, respectively) compared with those in the control (233.3 mg; 19.7 mm) and TN groups ( P < 0.05). Survival rates were similar across all groups, ranging from 33.8 to 38.2% ( P > 0.05). Larvae receiving Zn-Mn-enriched live foods also displayed enhanced antioxidant activity, with higher superoxide dismutase (SOD)and glutathione peroxidase (GPx), while catalase (CAT) activity was lower in the TO and TI groups, suggesting a shift toward a more efficient SOD-GPx-mediated redox regulation. Expression of osteogenesis-related genes (runt-related transcription factor 2b, bone morphogenetic protein 2, and osteocalcin ) was lower in the control and TA groups than in the TN, TO, and TI groups. The mnsod transcript level was higher in TA than in control and TN, while igf1 expression increased in the TO and TI groups relative to control and TA. In conclusion, Zn-Mn enrichment, particularly through microalgae or organic mineral sources, improved growth performance and enhanced antioxidant capacity in A. arabicus larvae, while direct mineral supplementation via nanoparticle or inorganic/organic emulsions more effectively promoted osteogenic gene expression.