noticed presumably because of the simultaneous salinity and tempera- 

 ture stress. The respiratory rates were in general well above the 

 control level despite the fact that the shrimp were under heavy 

 stress and were dying. 



Effect of 52°C acclimation on oxygen consumption 



The oxygen consumption of brown shrimp acclimated to 32°C is 

 shown in Figs. 106, 107, and 108. The mean control respiratory 

 level was higher than those acclimated to 18° or 25°C. The initial 

 shock effect in 18° and 25°C resulted in a sudden drop in the meta- 

 bolic rates from the control level. The control shrimp showed an 

 initial increase in the metabolic rate when tested at 32°C (Fig. 

 106); but in none of the salinities did this increase vary sig- 

 nificantly from the control after the first hour or two as though 

 the shrimp were less sensitive to salinity changes at 32°C (Table 

 13). It should be recalled that a similar lack of sensitivity was 

 observed in the behavioral responses of brown shrimp acclimated and 

 tested at 32°C. 



In contrast, the shrimp acclimated to 32°C exhibited significant 

 metabolic variations between the test salinities at 18° and 25°C 

 (Figs. 107 and 108). At 18°C these variations (P=0.01) were present 

 in nearly all salinities (Table 14). However, at 25°C they were con- 

 fined to 2, 5, and 15°/ooS while none were observed in 36°/ooS 

 (Table 15). The shrimp experienced more initial shock in 18°C than 

 in 25°C, indicating that the magnitude of the shock increased with 

 temperature difference between acclimation and test conditions. 



Stabilization of the metabolic responses commenced within two 

 hours after transfer to 18°C and 32°C and within four to six hours 

 at 25°C. The animals in 25°C attained new steady-state respira- 

 tory levels within a day in 10, 15, 25, and 36°/ooS while at 18°C 

 these levels appeared in 10 and 15°/ooS. Also at 25°C the survival 



213 



