ACCUMULATION OF UREA IN THE HEMOLYMPH AND AMMONIA EXCRETION OF PENAEUS-JAPONICUS EXPOSED TO AMBIENT NITRITE

Penaeus japonicus (15.7 +/- 1.4 g) were exposed individually in 30 ppt seawater to 0.01 (control), 5, 10, 20 and 50 mg/l nitrite-N for 24 hr, Haemolymph ammonia, urea, nitrite and whole shrimp ammonia-N excretion and nitrite-N uptake were then determined. Ammonia excretion of P. japonicus increased with increased ambient nitrite, and with a concomitant decrease of haemolymph ammonia, as occurring increased concentrations of nitrite. Concentrations of nitrite-N and urea-N in the haemolymph of shrimp increased with increased ambient nitrite-N. However, no urea-N excretion was observed for shrimp exposed to any nitrite treatments.