Two of them were under stress by eight hours but none were dead by 

 the end of the test period (Table 26) . The times at which stress 

 began in 1, 5, and 6% Mg were erratic, as were the death rates. 

 There was one death in 6% Mg and two in 1% Mg. The latter deaths 

 occurred after molting. 



At 18°C reduced magnesium had little effect on survival rates 

 within the 24 hour period. A few cases of stressed animals were 

 present in 0, 1, and 6% Mg with only one death in 0% Mg. 



At 32°C more animals exhibited stress than in 18° or 25°C. 

 Four shrimp died in 0% Mg during the 24 hour period. One animal 

 each in 1% and 6% Mg became stressed, and they were later killed 

 and eaten by the others. The feeding response usually indicates 

 the presence of normal behavior. 



Effect of Deviated Cation Concentrations in Low Salinities 

 on the Behavior and Survival 



Brown shrimp were acclimated separately for one week in synthetic 

 seawater of 5 and 10°/ooS concentrations at 25°C temperature. The 

 acclimated animals were tested in the respective control salinities 

 having normal ion concentrations and in salinities with deviated 

 cation concentrations. Their behavior and survival rates were de- 

 termined in each condition (Table 27). 



In 5°/oo control salinity the shrimp were somewhat more active 

 than the animals tested in either 10 or 15°/ooS at 25°C. Otherwise 

 the general beK-avior was normal in both 5 and 10°/ooS. One shrimp, 

 however, developed cramps in 5°/ooS. 



Effect of deviated sodium 



In both salinities 5 and 10°/oo there was no marked effect of 

 decreased or increased sodium concentration on the behavior and 



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