IV: DISCUSSION 



Time Course of Sal inity A daptation 



The results demonstrate that salinity adaptation in brown shrimp 

 depends upon the magnitude as well as the direction of salinity or 

 temperature change. The data also show that the metabolic rates, 

 determined on the basis of oxygen uptake rates, change in accordance 

 with the external salinity or temperature conditions. Alterations in 

 the metabolic rates are usually associated with changes in osmotic 

 and ionic concentrations of body fluids. Changes in the functional 

 responses indicate that the adaptation to salinity or temperature 

 occurs through immediate regulation, stabilization, and steady-state 

 phases. Blood chloride ion regulation generally parallels the osmoreg- 

 ulation. Minor ionic deviations apparently do not affect brown shrimp 

 adversely, but major changes in calcium and potassium seem to create 

 severe physiological problems and threaten their survival. 



Salinity adaptation in brown shrimp is apparently related mainly 

 to their background on the one hand and to the deviation in test sa- 

 linity and temperature conditions on the other hand. The simplest 

 case of salinity adaptation was observed in animals acclimated and 

 tested at 25°C in a salinity range of 2 to 36°/oo. In these test 

 salinities, maximum initial changes in the respiratory rates oc- 

 curred within two hours. This was followed by another few hours 

 of stabilization. New metabolic steady-state levels were finally 

 reached in less than a day, which indicate the completion of sa- 

 linity adaptation. 



In the same test conditions the initial osmotic and ionic 

 changes occurred within two hours in 5, 10, 15 (control), and 

 25°/ooS and in six hours in 2 and 36°/ooS. Both osmotic stabili- 

 zation and steady-state levels were obtained in less than a day. 



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