increase from 25° to 32 °C and a comparison of the means showed a 

 significant difference (Table 20), On the contrary, the shrimp 

 acclimated to 18°C and tested in 5°/ooS (Fig. 114) did not show 

 significant differences in the oxygen consumption levels between 

 25° and 32°C (Table 21). But in 36°/ooS significant temperature 

 related differences were found between 25° and 32°C. Comparisons 

 in 2°/ooS were not valid due to the high mortality. 



These findings suggest that the shrimp acclimated to 25°C 

 were apparently less sensitive to temperature increase in very 

 dilute or in more saline media. The shrimp acclimated to 32° 

 or 18°C were more temperature-sensitive in low (5°/oo) or in 

 high (36°/oo) salinities, respectively. 



Effect of Temperature Background on Adaptation 



Adaptation to a single factor, i.e. salinity or temperature, 

 was found to occur faster than to two simultaneously changed 

 factors; but in nature brown shrimp are simultaneously exposed 

 to several environmental variables. As such, it is important to 

 know the salinity and temperature combinations to which the shrimp 

 can adapt quickly. The background environmental factors, particu- 

 larly temperature, seemed to influence the salinity and temperature 

 adaptation considerably. In order to understand some of these 

 processes, the metabolic response curves were reproduced from the 

 different adaptation conditions in Figures 115, 116, and 117. 



Brown shrimp which were adapted to 18° or 32°C were found 

 from the respiratory rates to re-adapt faster to their original 

 control conditions (15°/ooS and 25°C) (Fig. 115). A comparison 

 of the respiratory means between the three groups of shrimp in 

 15°/ooS showed no significant differences (Table 22). However, 

 in salinities other than control, the rate of adaptation varied 



241 



