Accumulation of ammonia in the hemolymph of Penaeus japonicus exposed to ambient ammonia

Abstract

Penaeus japonicas (14.12 0.74 cm, 13.91 ± 0.65 g) were exposed individually in 34 ppt seawater to 5, 10, 50 and 100 mg | 1 ammonia-N (un-ionized plus ionized ammonia as nitrogen) at pH 8.2: additional trials were run using 100 mg 1 -1 ammonia-N at pH 6.3 7.2, 8.2 and 9.0. Background hemolymph ammonia values were 4.45 ± 0 44 mg I - and 3 00 ± 0.32 mg | -1 ammonia-IN, respectively, for shrimp feeding normally and shrimp starved for 2 d. Shrimp exposed to 5, 10, 50 mg | -1 and controls survived 16 h trial exposures. No significant difference (p > 0.05) in hemolymph ammonia was observed between controls and shrimp exposed to 5 mg I - l for 16 h. However, hemolymph ammonia of shrimp exposed to 10, 50 and 100 mg I - was significantly higher (p < 0.05) after 2 h exposure than for controls. Hemolymph ammonia of shrimp exposed to 100 mg I - I ammonia-N at pH 9.0 was significantly higher (p < 0.05) than of those exposed to the same concentration at pH 6.3, 7.2 and 8.2. Shrimp exposed to 100 mg I -l ammonia-N at pH 9.0 and 8.2 accumulated maximal concentrations of ammonia in 30 min and 12 hr respectivr ely. Those exposed to 50 mg I - l ammonia-N at pH 8.2 reached a maximum after 16 h Both NH3 (un-ionized ammonia) and NH<+ affected ammonia accumulation and caused death; shrimp which had accumulated ammonia-X in the hemolymph to a level of 20 mg I - l were weakened and eventually died.