36°/ooS at the three test temperatures and in 2 and 5°/ooS at 25° and 

 32°C. In 2, 5, 10, and 15°/ooS stabilization in the magnesium ion 

 regulation started within two to six hours at 25 °C (Fig. 31) . In 

 high salinities, especially 36°/ooS, it was a much slower process. 

 Stabilization progressed at the same rates in 32°C (Fig. 32) and 

 18°C (Fig. 33) . In 25 and 36°/ooS media, individual variations in 

 the ion regulation were very high as shown in the standard deviation 

 values (Figs. 31, 32, and 33). 



The shrimp acclimated and tested at 25°C apparently reached new 

 steady-state levels in all but 36°/ooS (Fig. 31). At 32°C, however, 

 the animals were still in the process of stabilization in 10, 15, 25, 

 and 36°/ooS by the time the tests were concluded (Fig. 32) ; in 2 and 

 5°/ooS steady-state levels were apparently reached. In 18°C it was 

 doubtful whether steady-state levels were attained in salinities 

 other than 2°/ooS (Fig. 33). 



The shrimp acclimated to 32°C had the lowest control mean ion 

 concentration of the acclimation temperatures. The initial response 

 of shrimp acclimated to 32°C was a sudden increase in the magnesium 

 ion concentration. The responses continued from four to six hours 

 in 2, 5, 10, and 15°/ooS and longer in 25 and 36°/ooS at the three 

 test temperatures (Figs. 34, 35, and 36). Stabilization of ion 

 regulation at 32°C started within six hours in 2, 5, 10, and 15°/ooS, 

 within a day after the transfer in 25°/ooS, but apparently not in 

 36°/ooS (Fig. 34). At 25°C a similar pattern was noticed in the 

 respective salinities (Fig. 35) . In 18°C the shrimp started the 

 stabilization process on the first day itself in salinities from 2 

 to 25°/oo (Fig. 36) . In 36°/ooS the process commenced two days later. 

 At 32°C new steady-state levels were attained in all salinities ex- 

 cept in 36°/ooS, while at 25°C these levels were seen in 2 and 10°/ooS 

 only. At 18°C steady-state levels appeared in 5, 10, and 15°/ooS but 

 not in other concentrations. 



95 



