Acute toxicity of ammonia in white shrimp (Litopenaeus schmitti) (Burkenroad, 1936, Crustacea) at different salinity levels

Litopenaeus schmitti juveniles (total length 15 +/- 0.7 mm) were exposed to different concentrations of ammonia-N (un-ionized plus ionized ammonia as nitrogen), using the static renewal method at different salinity levels (5 parts per thousand, 20 parts per thousand and 35 parts per thousand) at pH 8.0 and 20 degrees C. The 24, 48, 72, 96 h LC50 values of ammonia-N in L. schmitti juveniles were 40.72, 32.63, 24.63, 19.12 mg l(-1) at 5 parts per thousand; 53.52, 38.60, 27.76, 25.55 mg l(-1) at 20 parts per thousand; 54.32, 47.87 and 41.67, 38.88 mg l(-1) at 35 parts per thousand salinity. The 24, 48, 72, 96 h LC50 values of NH3-N (un-ionized ammonia as nitrogen) were 1.46, 1.17, 0.88, 0.69 mg l(-1) at 5 parts per thousand; 1.80, 1.30, 0.93, 0.86 mg l(-1) at 20 parts per thousand and 1.67, 1.47, 1.28, 1.20 mg l(-1) at 35 parts per thousand salinity. As the salinity decreased from 35 parts per thousand to 5 parts per thousand, susceptibility of ammonia-N increased by 33.4%, 46.7%, 69.2% and 103.3%, after 24, 48, 72 and 96 h of exposure, respectively. Furthermore, we found that exposure of shrimp to ammonia-N caused an increase in oxygen consumption of 137.3%, 99.2% and 81.4% and an increase in the ammonia excretion level of 112.5%, 87% and 64.3% with respect to the control. (C) 2010 Elsevier B.V. All rights reserved.