Chloride regulation 



Blood chloride concentration increased with salinity increase 

 from 2 to 36°/ooS (Fig. 81). The blood chloride ion curves were 

 isosmotic with the test salinities between 20 and 22°/ooS level. 

 The chloride ion regulation was more efficient in the range of 5 to 

 25°/ooS than in other salinities. However, regulatory variations 

 occurred within this salinity range, depending upon the acclimation 

 and test temperatures. The shrimp acclimated to 18°C appeared to 

 regulate the chlorides better in the three test temperatures than 

 those acclimated to 25° or 32 °C. On the other hand, the shrimp ac- 

 climated to 32°C appeared to be the least efficient regulators with 

 the result that the ion regulation in 25 and 36°/ooS was almost 

 parallel to the isosmotic line (Fig. 81). The wide separation of 

 the response curves of shrimp acclimated to 18°C and tested in 25° 

 and 32°C indicate a possible temperature sensitivity. Furthermore, 

 except for the shrimp acclimated at 18°C the others maintained a lower 

 chloride level in their acclimation temperatures than in test tempera- 

 tures. 



Calcium regulation 



The blood calcium generally increased with the external salin- 

 ities (Fig. 82). In the lower salinity range of 2 to 15°/ooS this 

 increase was less proportionate than in higher salinities. In 25 

 and 36°/ooS the extent of increase was high and out of proportion. 

 The blood calcium level was maintained hyperosmotic to the isosmotic 

 line throughout the test salinity range with one exception; in 36°/ooS 

 the shrimp acclimated and tested in 18°C maintained a slightly hypos- 

 motic level. 



The rate of calcium increase was similar in the various sa- 

 linities in animals acclimated to 25°C and tested in 18°, 25°, and 

 32°C. But the animals acclimated and tested at 32°C showed great 

 differences from those tested at 18° and 25 °C and maintained the 



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