Ammonia-induced Disruption of Metabolic and Antioxidant Pathways in the Gill, Hepatopancreas, and Muscle of Macrobrachium rosenbergii.

Ammonia accumulation is a major constraint in intensive Macrobrachium rosenbergii aquaculture, yet the mechanisms linking multi-organ injury to tissue deterioration remain unclear. Juvenile prawns were exposed for 7 days to 0, 2, and 50 mg L⁻¹ total ammonia nitrogen (TAN) to evaluate integrated physiological, histological, transcriptomic, and metabolomic responses in gill, hepatopancreas, and muscle. Survival decreased from 100% in controls to 89% and 75% at 2 and 50 mg L⁻¹, respectively, accompanied by gill lamellar disruption, hepatopancreatic tubule degeneration, and muscle fiber separation. RNA-seq identified 4,944 differentially expressed genes with strong organ-specific patterns. The hepatopancreas showed enhanced lysosomal activity and redox defenses, the gills exhibited disrupted nitrogen and lipid metabolism, and the muscle displayed impaired glycolysis and altered structural protein signaling. Changes in CD63, CssYP2J, GLUL, and AIFM1 expression, together with altered CAT, GS, and GDH activities, indicated adaptive detoxification at moderate TAN. However, high TAN overwhelmed these responses, leading to glutamine detoxification failure, lipid peroxidation, and malondialdehyde accumulation. Gill metabolomics revealed TAN-dependent alterations in carbon, amino acid, and phospholipid pathways, particularly glycerol-phosphocholine, citric acid, and citrulline metabolism, highlighting metabolite-gene interactions within nitrogen and membrane lipid networks. Overall, even sublethal TAN acted as a systemic stressor, reprogramming metabolic and antioxidant pathways across organs, with muscle emerging as the most vulnerable tissue. These findings refine ammonia toxicity thresholds and support maintaining TAN below 2 mg L⁻¹ to protect prawn health and aquaculture sustainability.