increased from a lowest level in 18°C to a highest in 32°C. This 

 pattern was seen throughout the salinity range. Animals tested at 

 25°C responded like those in 32°C in most of the salinities. 



No significant deviations were seen from the above pattern in 

 shrimp acclimated to 32°C and tested in 18°, 25°, and 32°C (Fig. 98). 

 The shrimp tested in 18°C maintained a lowest ion concentration in 

 all salinities. The important difference was that in 25°C the potas- 

 sium levels were highest in 5, 10, and 15°/ooS. The shrimp tested 

 in 25° and 32°C responded almost identically in 2 and 36°/ooS. 



In shrimp acclimated and tested in 18°C (Fig. 99) the potassium 

 levels did not increase from the previous lowest levels. The low 

 potassium levels indicated that by acclimation to 18°C the shrimp 

 derived no advantage with respect to altering the potassium regu- 

 lation. In 32°C the shrimp held the highest ion levels. However, 

 the shrimp acclimated to 18°C became more temperature sensitive. 

 This was indicated by the wide separation of temperature -related 

 response curves from each other except in 36°/ooS. The animals 

 tested in 25°C responded similarly as in 18°C in 2 and 36°/ooS 

 while in other concentrations they reacted more like those tested 

 in 52°C. 



Effect of Sex on Osmotic and Ionic Regulation 



The results of t tests comparing mean levels of blood osmolality 

 and ionic concentrations in male and female brown shrimp are given in 

 Tables 2 through 6. Significant differences (P=0.01 or 0.001) were 

 noted in a few isolated cases but there was no consistent pattern. 

 It appeared, therefore, that sex of the shrimp within the size 

 range used in these studies had no effect on ionic or osmotic regu- 

 lation. 



178 



