The stabilization process commenced within hours after transfer 

 to 32°C and new steady-state levels were established by the third or 

 fourth day. These levels in 2, 5, and 15°/ooS were similar to those 

 at 25°C, while in 25 and 36°/ooS the levels were slightly higher. 

 However, it should be mentioned that as a result of temperature 

 change from 25°C stabilization and steady-state processes were de- 

 layed. The delay was even longer at 18°C. 



It was reported above that the duration of salt loss was longest 

 in 18°C. Also in this temperature the extent of initial loss was 

 greatest. However, the regulatory capacity subsequently improved and 

 part of the salt losses were recovered. New steady-state levels were 

 established after the third or fourth day in most salinities. Another 

 major deviation in 18°C from 25° and 32°C test temperatures was the 

 presence of greater ionic fluctuations by individual shrimp, particu- 

 larly in 2, 5, and 10°/ooS. This conclusion was based on the high 

 standard deviation values. 



Effect of 32"'C acclimation on osmoregulation 



The blood osmotic concentration levels in brown shrimp accli- 

 mated to 32°C and 15°/ooS are shown in Figures 7 to 9. The control 

 shrimp (32 °C) maintained slightly higher osmoconcentration levels 

 than their counterparts acclimated and tested in 25°C (657 mOsm com- 

 pared with 643 mOsm, respectively) . However, the response pattern was 

 similar in both groups with respect to the test salinities. In 2, 

 5, and 10°/ooS there was an initial loss of salts while in 25 and 

 36°/ooS there was a salt gain (Fig. 7). The duration of initial 

 osmoregulatory changes in 32°C test temperature was longer than in 

 animals acclimated and tested in 25°C. The immediate responses con- 

 tinued from four to six hours in all salinities except in 25°/ooS. 

 When the shrimp were transferred to other test temperatures 25°C 

 (Fig. 8) and 18°C (Fig. 9) , the duration of the initial salt changes 

 continued from four to six hours in most of the conditions. However, 



67 



