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

Abstract

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‰, 20‰ and 35‰) at pH 8.0 and 20 °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‰; 53.52, 38.60, 27.76, 25.55 mg l − 1 at 20‰; 54.32, 47.87 and 41.67, 38.88 mg l − 1 at 35‰ salinity. The 24, 48, 72, 96 h LC50 values of NH 3-N (un-ionized ammonia as nitrogen) were 1.46, 1.17, 0.88, 0.69 mg l − 1 at 5‰; 1.80, 1.30, 0.93, 0.86 mg l − 1 at 20‰ and 1.67, 1.47, 1.28, 1.20 mg l − 1 at 35‰ salinity. As the salinity decreased from 35‰ to 5‰, 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.