Fig. 62) than in 32°C, especially in low salinities. AT 18°C shrimp suf- 

 fered heavy chloride losses in 2 and 5°/ooS (Fig. 63). After the second 

 day, however, the ions were recovered to a considerable extent in 5°/ooS 

 but not in 2°/ooS. There was also a high mortality rate in 2°/ooS. 



The brown shrimp which were acclimated to 18°C appeared to have 

 effectively controlled the chloride ion levels in 18°C (Fig. 64), 25°C 

 (Fig. 65), and 32°C (Fig. 66). Also the control shrimp in 15°/ooS and 

 18°C maintained the highest mean chloride concentration (298 mEq/L) of 

 all the control temperatures. The mean control levels decreased with 

 increased acclimation temperatures- -292 mEq/L at 25°C (Fig. 58) and 283 

 mEq/L at 32°C (Fig. 61) . The initial rapid ionic losses observed in 2, 

 5, and 10°/ooS at 18° and 32°C were recovered partly by the second day. 

 The steady-state chloride levels at 32°C were established more closely 

 to that of shrimp in 15°/ooS than at 18°C. In 2S°C the chloride ion 

 changes were minimal in both dilute and saline media with respect to 

 changes at 18° and 32°C. At 25°C there was no apparent attempt to 

 increase the blood chloride ion concentration from the initially low- 

 ered levels in the dilute media as occurred in 18° and 32°C. 



Calcium concentration 



Calcium ion concentration increased with the test salinities but 

 the raise was not consistent in relation to salinity increases in the 

 range of 5 to 15°/ooS. Brown shrimp acclimated and tested at 25°C (Fig. 

 67b) exhibited a hyposmotic calcium ion concentration in 2°/ooS and 

 hyperosmotic concentrations in 5, 25, and 36°/ooS in relation to the 

 level in the control salinity. In 10 and 15°/ooS the concentrations 

 were isosmotic. In 25 and 36°/ooS the ion levels increased more at 

 32°C (Fig. 67c) than at 25°C but decreased at 18°C (Fig. 67a). Calcium 

 ion concentration was hyposmotic in 2, 5, 10, and 15°/ooS at both 18° 

 and 32°C. In 5°/ooS the calcium level was almost equal to the control 

 level at 32°C and exceeded it at 25°C. 



129 



