Urea excretion by Penaeus japonicus Bate exposed to different concentrations of ambient ammonia

Abstract

Subadult Penaeus japonicus Bate (16.45 ± 2.25 g) were exposed individually in 30 ppt to 0.045 (control), 5.166, 10.163, 20.091 and 51.462 mg/l ammonia-N for 24 h. Accumulations of ammonia and urea in the haemolymph, and ammonia and urea excretions were determined; additional determinations were made for haemolymph nitrite accumulation and nitrite excretion. Background concentration of ammonia-N, urea-N and nitrite-N in the haemolymph of shrimp was 8.816 μg/ml, 0.028 μg/ml and 0.047 μg/ml, respectively. Accumulation of ammonia-N, urea-N and nitrite-N in the haemolymph, and urea-N and nitrite-N excretions of shrimp increased with increased ambient ammonia-N in the range of 0.045–51.462 mg/l. Ammonia-N excretion in the control animals was 2.310 μg/g/h. However, ammonia-N uptake of shrimp occurred, and increased with increased ambient ammonia-N in the range of 5.166–51.462 mg/l. Concentration of ambient ammonia-N at 20.091 mg/1 significantly caused (p < 0.05) shrimp from ammonotelism to ureotelism in 24 h.