36°/ooS the initial salt influx could not be controlled for about 

 four hours at 25°C and for 24 hours at 18°C. At 25°C the ionic 

 regulatory fluctuations were lowest of all the test temperatures. 

 However, in dilute media the ion loss continued from four to six 

 hours. The same types of responses were also seen at 18°C. At 18°C 

 the chloride ion regulation seemed to stabilize within four to six 

 hours in all media except 2 and 36°/ooS. 



At 25° and 32''C steady-state chloride ion levels appeared in 

 5, 10, 15, and 25°/ooS within the test period. The steady-state 

 levels occurred from the first day in 10, 15, 25, and 36°/ooS and 

 after two days in 2 and 5°/ooS. In 18°C evidently the salinity 

 adaptation was incomplete except in 10 and 15°/ooS. 



Effect of 18°C acclimation on chloride regulation 



The brown shrimp acclimated to and tested in 18°C (Fig. 19) ini- 

 tially lost chlorides in the dilute media. But part of these initial 

 losses were made up during the stabilization process and the new levels 

 were nearly on par with those in 25°C (Fig. 20) or 32°C (Fig. 21). At 

 18°C the initial responses continued in the various salinities from one 

 to six hours (Fig. 19). In 10, 15, 25, and 36°/ooS a steady state was 

 reached by six hours, while in 2 and 5°/ooS it was much later, by the 

 fourth day. 



New steady states were obtained in all salinities except 2, 5, 

 and 36°/oo within one day. In 5 and 36°/ooS steady states appeared 

 after four days at 32°C while in the other salinities, these levels 

 appeared after one day. At 32 °C great fluctuations were present in 

 the chloride ion regulation in 2 and 36°/ooS between the time inter- 

 vals and the individual shrimp. 



Time Course of Regulation of Other Ions 



Calcium, magnesium, and potassium ions represent a minor portion 

 of the blood osmoconcentration in comparison with chloride and sodium. 



77 



