Calcium ion 



In 2, 5, 10, and 15°/ooS the shrimp acclimated and tested in 

 25°C maintained higher calcium concentrations [Fig. 91) than those 

 acclimated and tested in 32° or 18°C. At 32° or 18°C test conditions 

 the shrimp experienced a higher initial loss. Those losses were par- 

 tially retrieved later in the course of adaptation. In 25 and 36°/ooS 

 the ionic influx was controlled better at test temperatures 25° and 

 18°C than in 32°C. In 32°C conditions great ionic regulatory fluc- 

 tuations were observed during the acclimation process. 



Acclimation and testing in 32 °C obviously improved the ion regu- 

 lation efficiency of shrimp in most of the salinities (Fig. 92) . In 

 5, 10, and 15°/ooS the shrimp retained more calcium than in 25° and 

 18°C test temperatures. Also in 2 and 36°/ooS the ion regulation 

 was relatively stable among the shrimp tested at 32°C. The regulatory 

 pattern of the animals tested at 25° and 18°C was alike in 5, 10, 

 and 15°/ooS. 



The calcium ion regulation was improved in salinities above 

 10°/oo when the shrimp acclimated to 18°C were tested at the same 

 temperature (Fig. 93). For unknown reasons these animals lost more 

 calcium in 5, 10, and 15°/ooS during the tests at 25°C than in 18° 

 or 32°C; in 36°/ooS they failed to control the ion influx effectively. 

 Acclimation to 18°C did not impair the regulation efficiency in 32°C 

 particularly in 5, 10, and 15°/ooS media. 



Magnesium ion 



In the low-salinity range of 2 to 15°/oo the temperature effect 

 was not significant on the magnesium ion regulation. In salinities of 

 25 and 36°/oo temperature effect was present but without any trend. 



Brown shrimp acclimated and tested at 25°C (Fig. 94) maintained 

 a relatively low magnesium concentration in 2, 5, 10, 15, and 25°/ooS, 



169 



