Oxygen Consumption in Time Course of Adaptation 



Effect of 25°C acclimation on oxygen consumption 



Respiratory rates in Penaeus aztecus acclimated to 25°C are 

 shown in Figs, 100, 101, and 102 in the time course of adaptation. 

 The horizontal line is the control mean oxygen consumption in 

 15°/ooS and 25°C. Means are connected by solid lines and the 

 moving averages by broken lines. 



The shrimp experienced an initial shock effect following their 

 transfer into the test conditions. The sudden change in the oxygen 

 uptake indicated this effect in conjunction with the hyperactive 

 behavior under similar conditions. The immediate response resulted 

 in an overshoot in the oxygen uptake at 25° and 32°C (Figs. 100 and 

 101, respectively) and in an undershoot at 18°C (Fig. 102), a situa- 

 tion which occurred consistently throughout the salinity range. 



The shock effect was present for about two hours in 15°/ooS 

 (Fig. 100) and six hours in other salinities. Animals tested in 

 25°C showed significant variations (P=0.01) in their respiratory 

 rates (Table 7) in all salinities except 15°/ooS which indicated 

 their sensitivity to salinity changes. This was also documented 

 in their behavior. The shock effect increased when shrimp from 

 25°C were transferred to 32° and 18°C, The extent of the initial 

 shock can be understood from the significant differences existing 

 between the initial respiratory rates and the steady-state levels 

 at 32°C (Table 8) and 18°C (Table 9). 



Stabilization of respiratory rates commenced at 25°C faster than 

 in 32° and 18°C. At 25°C stabilization started in almost all salini- 

 ties within four hours after transfer and new steady-state levels 

 were established in less than a day. The criterion for a new steady 

 state was the flatness of the metabolic curve, the presence of 



186 



