Changes in hemolymph oxyhemocyanin, acid-base balance, and electrolytes in Marsupenaeus japonicus under combined ammonia and nitrite stress.

Ammonia and nitrite are the most common toxic nitrogenous compounds in aquaculture ponds. We evaluated the effects of a combined treatment with these two compounds on the hemolymph acid-base balance, electrolytes and oxyhemocyanin content in kuruma shrimp, (Marsupenaeus japonicus). The shrimp (6.37±1.29 g) were individually exposed to 9 different ammonia and nitrite regimes {ammonia at 0 (control), 0.39, and 1.49 mM combined with nitrite at 0 (control), 0.38, and 1.49 mM} in a 30‰ saline solution at 22°C. Hemolymph oxyhemocyanin (OxyHc), protein content, acid-base balance, osmolality, and electrolyte levels were measured in treated shrimp after 48 h of treatment. Hemolymph OxyHc, protein content, the OxyHc/protein ratio, pH, pCO2, HCO3(-), TCO2, OH(-)/H(+), osmolality, and Cl(-), Na(+), K(+), Ca(2+), and Mg(2+) levels were inversely related to the dose of ammonia and nitrite. However, hemolymph pO2 levels directly increased with the ammonia and nitrite concentrations. Following exposure to 1.49 mM ammonia+1.49 mM nitrite, the hemolymph pO2 increased by 89.5%, whereas the hemolymph OxyHc, protein content, OxyHc/protein ratio, pH, pCO2, HCO3(-), TCO2, OH(-)/H(+), osmolality, Cl(-), and Na(+) decreased by 51.2, 28.2, 34.9, 2.9, 51.1, 71.5, 70.8, 42.8, 4.9, 32.1, and 38.6%, respectively, compared with control shrimp. Combined ammonia and nitrite stress may therefore exert a synergistic effect on shrimp relative to the stress induced by ammonia or nitrite alone.