Effect of 18°C acclimation on oxygen consumption 



After seven days of acclimation in 15°/ooS and 18°C brown shrimp 

 were tested in 18° (Fig. 103), 25° (Fig. 104), and 32°C (Fig. 105). 

 The metabolic rates increased gradually with temperatures from 18°C 

 to 25° and 32°C. At 18°C the initial shock effect continued for a 

 maximum of two hours (Fig. 103) as opposed to longer periods in 25° 

 or 32 °C where the effect lasted for several hours. At a test tempera- 

 ture of 32°C, all shrimp were dead in 2°/ooS by four hours. Stabili- 

 zation commenced within two hours at 18°C and within a day in some 

 of the salinities in 25° and 32°C. The flatness of the metabolic 

 curve in 5 and 36°/ooS at 32°C should be considered with caution in 

 view of the high mortality rates. 



On the basis of visual examination of the metabolic curves, 

 statistical analyses of the respiratory means (Table 10) , and fa- 

 vorable survival rates, it appeared that the shrimp at 18°C attained 

 steady-state metabolic levels in all but 2°/ooS. The animals at 

 25°C attained such levels in 10, 15, and 25°/ooS within the first 

 day but not in 2, 5, and 36°/ooS where the mortality was also high. 

 Significant differences occurred in the respiration rates in most of 

 the media from the third day onward (Table 11); but the importance 

 of these variations was not clear. In 10 and 15°/ooS they might re- 

 flect starvation effect and in others, a recovery state from the ini- 

 tial shock. 



The shrimp acclimated to 18°C and tested in 32°C could not 

 establish steady-state metabolic levels within the test period in 

 salinities other than 10 and 15°/ooS. Steady-state level appeared 

 in 25°/ooS on the first day but all the shrimp died after six days. 

 From the statistical comparison the respiratory rates in 5 and 

 36°/ooS were erratic (Table 12). The extent of stress caused by a 

 sudden temperature change from 18° to 32°C was evident from the high 

 mortality in most of the salinities. The starvation effect was not 



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