quiescent. In 85% Na one shrimp was dead by 1-1/2 hours and two 

 others died after molting. Three shrimp died in 12 hours in 95% 

 Na and in 24 hours in 120% Na. The mortality rate did not indicate 

 any trend associated with the deviated sodium ion. It is likely 

 that the deaths were due to a combined effect of high temperature 

 (32°C) and deviated sodium concentration. 



Effect of reduced potassium 



In media of low potassium (K) concentration the brown shrimp 

 exhibited different levels of activity, experienced stress and mor- 

 tality, and developed paralysis and abdominal cramps. At 25 °C the 

 shrimp showed symptoms of stress in the medium with 10% K within 

 one hour after transfer. Five animals died after three hours. Out 

 of these, one was molted and two had become paralytic. The five 

 survivors were quiet. In 30% K the animals felt the stress from 

 six hours but only one shrimp died by 24 hours. The remaining 

 animals were active throughout the observation period. In 40, 50, 

 and 60% K the shrimp were initially hyperactive. Later some experi- 

 enced stress. Three shrimp died in 60% K as opposed to one in 40% 

 and none in 50% K. 



The incidence of abdominal cramping was high at 18°C. The rate 

 was six in 10% K, highest of all concentrations. The lowest rate was 

 two in 50% K. Usually cramps developed by six hours and continued 

 thereafter; they exhibited no trend in relation to the ionic concen- 

 tration. Mortality was lowest at 18°C, one each in 40% and 60% K 

 media. 



At 32 "C the mortality rate was higher than in the other tempera- 

 tures. The rate did not show any pattern because the highest number 

 of deaths occurred in 60% K. In 10% K, which was the lowest potassium 

 concentration, only four shrimp died. Lowest mortality was in 30% K. 

 Generally the shrimp were hyperactive in all the test media, possibly 



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