ACCUMULATION OF NITRITE IN THE HEMOLYMPH OF PENAEUS-MONODON EXPOSED TO AMBIENT NITRITE

1. Penaeus monodon (15.87 +/- 0.69 g) were exposed individually in 25 ppt seawater to 2, 4, 8 and 20 mg/l nitrite-N (nitrite as nitrogen) at 24 +/- 1-degrees-C. The background haemolymph nitrite values were 0.140 +/- 0.004 mug/ml nitrite-N. 2. Control animals and those exposed to all test solutions survived the 16 hr trial exposures. 3. Haemolymph nitrite-N of shrimp exposed to 2 mg/l nitrite-N was significantly higher (P < 0.05) than that of controls after half an hour exposure. 4. Haemolymph nitrite-N of the shrimp had a positive linear relationship with time. However, ambient nitrite-N had a negative exponential relationship with time. 5. Haemolymph nitrite-N of the shrimp increased with an increase of ambient nitrite-N. The shrimp exposed to 2, 4, 8 and 20 mg/l nitrite-N accumulated nitrite-N in the haemolymph up to 2.229, 6.849, 9.311 and 25.704 mug/ml after 16 hr with ambient nitrite-N declined to 0.070, 0.098 and 0.301 mg/l respectively. 6. A small increase of nitrite in the ambient environment affected nitrite accumulation in the haemolymph and caused moribundity of P. monodon.