Accumulation of ammonia in the nemolymph of Penaeus japonicus exposed la ambient ammonia

Abstract

Penaeuslaponicus (14.12 t 0.74 cm, 13.91 k 0 65 g) were exposed individually in 34 ppt seawater to 5, 10, 50 and 100 m g 1-' ammonia-N (un-ionized plus ionized ammonia as nitrogen) at pH 8.2: additional trials were run using 100 mg 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 k 0.32 mg 1-' ammonia-N, respectively, for shrimp feeding normally and shrimp starved for 2 d Shnmp exposed to 5 , 10, 50 m g 1-' and controls survived 16 h tnal exposures. No significant difference (p > 0.05) in hemolymph ammonia was observed between controls and shrimp exposed to 5 mg I-' 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 m g 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 Shrlmp exposed to 100 mg I-' ammonla-N at pH 9.0 and 8.2 accumulated maxi~nal concentrations of ainmonia In 30 mm and 12 h , respectively. Those exposed to 50 mg I-' ammonia-N at pH 8 2 reached a maximuin after 16 h Both NH3 (un-ionized ammonia) and NH,+ affected ainmonia accumulation and caused death; shrimp which had accumulated ammonia-l"] in the hemolymph to a level of 20 m g I-' were weakened and eventually died.