Therefore, total salt and chloride ion levels were generally maintained 

 parallel to each other. The chloride ion concentration was hyposmotic 

 in 2, 5, and 10°/ooS and hyperosmotic in 25 and 36°/ooS in relation to 

 the ionic level among shrimp in 15°/ooS. This trend was consistent, 

 regardless of acclimation or test temperature. Animals acclimated and 

 tested in 25°C showed relatively few variations in the chloride ion con- 

 centration levels in 5, 10, 15, and 25°/ooS (Fig. 58). It would indi- 

 cate that at normal temperature (25°C) the concentration of chloride 

 ions was less affected by salinity change within the 5 to 25°/ooS range. 

 In 2 and 36°/ooS the changes were much greater. However, the mortality 

 rate in 2 and 36°/ooS was zero. 



Large fluctuations in the chloride ion concentrations occurred be- 

 tween the first and 96th hours at 32°C (Fig. 59). The fluctuations 

 were even greater at 18°C (Fig. 60) . The salinity-related response 

 pattern at 32°C was similar to that at 25°C. There was a rapid initial 

 chloride ion loss at 18°C in 15°/oo and lower salinities. Part of the 

 initial ionic losses at 18°C were eventually recovered. As a result, 

 at 18° and 32°C the new steady-state levels in all salinities except 

 36°/oo were either equal to those at 25°C or slightly higher, as in 

 2 and 10°/ooS at 18°C. 



The shrimp acclimated and tested at 32 °C experienced large fluc- 

 tuations in chloride concentration, particularly in 2, 5, 25, and 

 36°/ooS (Fig. 61). Also, the resistance to ion influx in 25 and 

 36°/ooS was less effective than in shrimp acclimated and tested in 

 25°C (Fig. 58) . Consequently at 32°C the steady-state levels in 25 

 and 36°/ooS were less effective than in shrimp acclimated and tested 

 in 25°C (Fig. 58) . Consequently at 32°C the steady-state levels in 

 25 and 36°/ooS were held at higher levels than in the other group. 

 In 2, 5, and 10°/ooS, although initial fluctuations were present in 

 the levels, the final steady-state levels did not vary from those of 

 25°C acclimation. Shrimp acclimated to 32°C were obviously more 

 efficient in controlling the chloride ion concentration in 25°C 



124 



