V: SUMMARY 



The time course of salinity adaptation is determined in Penaeus 

 aztecus by studying their behavioral and physiological responses. 

 These responses include survival and metabolic rates, blood osmotic 

 and ionic regulation of chloride, magnesium, calcium, and potassium. 



Experimental shrimp of 95 mm mean length were acclimated for 

 about a week to 18°, 25°, and 32°C in a control salinity of 15°/oo. 

 The acclimated shrimp were then transferred separately to 2, 5, 10, 

 15, 25, and 36°/ooS for salinity adaptation at 18°, 25°, and 32°C. 



At 25°C the activity level and other behavioral responses were 

 influenced mainly by salinity changes from the control salinity. At 

 other temperatures (18° and 32°C) the interaction of salinity and 

 temperature apparently determines these responses. 



Three phases--immediate responses, stabilization, and new steady- 

 state levels--were recognized in the salinity adaptation process. 

 The duration of each phase varied with the test condition. The 

 attainment of steady states of metabolic and osmotic or chloride 

 levels indicated the completion of adaptation to the respective con- 

 ditions. 



Salinity adaptation was faster in 25°C than in 18° or 32°C. It 

 occurred in a wider range from 2 to 36°/ooS within a week. The range 

 of adaptation decreased from 5 to 25°/ooS at 18°C, and from 10 to 

 25°/ooS at 32°C. In these salinity ranges mortality was low during 

 adaptation. Outside of these salinity ranges adaptation was slower. 

 Adaptation to some conditions was not possible by direct transfer. 



Prior acclimation of shrimp to 18° or 32 °C accelerated the rate 

 of adaptation in the respective test temperatures. Also the range 



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