Brown shrimp acclimated to 32°C were tested in 32°C (Fig. 43), 

 25°C (Fig. 44), and 18°C (Fig. 45). Maximum changes occurred in the 

 ion concentration during the immediate response phase which lasted 

 from one to six hours. The ion regulation was stabilized within 

 three days at both 25° and 32°C in all salinities. The process was 

 relatively slower at 18°C and continued on through the fourth day. 

 While the steady-state levels in most of the salinities at 25° and 

 32°C started from the third day itself, it was doubtful whether 

 these levels were established at 18°C except on the basis of moving 

 averages. The steady-state levels at 18°C were mostly below the 

 control level (15°/ooS) while at 25°C they were above the control. 

 Tlie low sample size in 2°/ooS was a result of heavy mortality. 



The control mean potassium level of shrimp acclimated to 18°C 

 was 6.3 mEq/L, which was lower than 8.8 mEq/L at 25°C and 8.5 mEq/L 

 at 32°C. When the animals were tested at 18° (Fig. 46), 25° (Fig. 

 47), and 32°C (Fig. 48), the immediate responses continued up to a 

 maximum of ten hours in the extreme salinities. In other concentra- 

 tions the duration was from one to two hours. High fluctuations 

 occurred in the ion regulation in salinities of 2, 5, 25, and 36°/oo. 

 New steady-state levels appeared at 18° and 32°C in all but 25°/ooS 

 after the third or fourth day. However, on the basis of moving aver- 

 ages these levels were also established in 25°C. The regulatory 

 fluctuations were also high at 25°C. 



Effect of Salinity Change on Osmotic and Ionic Concentration 



The effects of salinity change on the osmotic and ionic concen- 

 trations of brown shrimp will be described in relation to the blood 

 ionic and osmotic concentrations of animals in the control salinity 

 and temperatures. In the next section these effects will be described 

 with respect to the isosmotic concentration levels of the test salini- 

 ties. Tlie figures shown in this topic were made with moving averages. 



106 



