Effect of ammonia and salinity on growth, molting periods and calcium in exoskeleton of black tiger shrimp (Penaeus monodon Fabricius)
1997
Suriya Chankaew
The 96-h LC50 of ammonia to Penaeus monodon with an average weight of 0.81+-0.17, 1.59+-0.24, 2.46+-0.25 and 3.47+-0.67 g in 10, 20 and 30 ppt seawater using the static renewal method were 12.81, 18.69, 24.34 and 25.99 mg/l ammonia-N; 15.27, 20.62, 29.49 and 25.79 mg/l ammonia-N; 19.0, 27.79, 30.43 and 32.74 mg/l ammonia-N respectively. The EC50 (Concentration that reduced growth by 50 percent of the control) of ammonia-N (unionized plus ionized as nitrogen) and NH3-N (unionized ammonia-N) at 10, 20, 30 ppt for 60 days period were 15.30, 17.35, 16.81 mg/l ammonia-N and 0.53, 0.48 and 0.50 mg/l NH3-N respectively. The MATC (maximum acceptable toxicant concentration) for 60 days at 10, 20 and 30 ppt were 3.5, 7 and 3.5 mg/l for ammonia-N and 0.15, 0.29 and 0.26 mg/l NH3-N for unionized ammonia. Increasing of ammonia caused reduction in molting period of 1st intermolt to 2nd intermolt. Experiment at 10, 20 and 30 ppt showed that the shortest molting period occured at 10 ppt. The molting period at 10 ppt for the control, 3.5, 7 and 14 mg/l ammonia-N were 11.45, 10.23, 9.49 and 9.31 days respectively. At salinity of 10 and 30 ppt, calcium content in shrimp muscle kept in control and expose to 3.5, 7 and 14 mg/l ammonia-N were 1.137, 1.249, 1.635 and 2.246 mg/g and 2.462, 2.548, 2.603 and 2.824 mg/g respectively. Increased ammonia directly raised calcium content in shrimp muscle. However, calcium content in exoskeleton and intermolt exoskeleton were not affected by ammonia but increasing salinity raised calcium content in both of the exoskeleton.
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