Metabolic, immune responses in prawn (Penaeus monodon) exposed to ambient ammonia

This article reports on the changes in the metabolic detoxification indices of the hepatopancreas, muscle, and gill tissues of juvenile prawn (body length of 5.0 +/- A 0.5 cm) of Penaeus monodon at different ammonia levels (at concentrations of 0, 10, 20, and 30 mg/L) as well as the immune-related gene expressions of the prawn under elevated ammonia (30 mg/L) stress. Results showed that glutamine synthetase (GS) activity and glutamine (Gln) content were higher in the muscle than those in the gill and hepatopancreas, not only at the normal level but also under stress. The GS activity and the Gln concentration at 96 h were significantly higher than those in the control group (p < 0.05) and positively correlated with the ammonia concentration from 0 to 48 h. The gene expressions of C-lysozyme, antibacterial peptide (crustin), and antilipopolysaccharide factor in P. monodon were upregulated at the initial period and downregulated at the later period under high ammonia stress (30 mg/L ammonia), except for the crustin gene in muscle, which maintained a continuous high expression from 0 to 96 h (p < 0.05). Our results confirmed that ammonia stress induced a detoxification metabolic pathway at least dependent on Gln synthesis in juvenile prawn. Body immunity was also activated at the initial period and decreased at the later period of high ammonia stress. Muscle is a sensitive tissue reflecting the ammonia stress state not only by physiological index but also by crustin mRNA level in juvenile prawn.