Effect of 18°C acclimation 



The shrimp acclimated and tested in 18°C (Fig. Ilia) showed some 

 similarities in oxygen consumption with those acclimated to 25°C and 

 tested in 18°C (Fig. 109a), The oxygen uptake in 2°/ooS was high 

 until the shrimp died in a state of hyperactivity. In 5°/ooS the 

 respiratory rates were low despite the fact that the shrimp were 

 not depressed. The respiratory means in 15°/ooS exhibited signifi- 

 cant differences (P=0.01) with other test salinities (Table 18). 

 However, the rates were similar between 10°/ooS and both 25 and 

 36 /ooS. 



The initial respiratory rates at 25°C were higher than in sub- 

 sequent intervals in 2 and 36°/ooS and lower in 10 and IS^/ooS 

 (Fig. 111b). The shrimp acclimated and tested at 25°C exhibited a 

 similar pattern in relation to the salinity changes (Fig. 109b). 

 Respiratory rates between 2 and 25°/ooS and between 2 and 36°/ooS 

 did not exhibit significant variations nor did comparisons between 

 5 and 15°/ooS and between 5 and 36°/ooS (Table 18). 



The brown shrimp acclimated to 18°C and tested in 32°C consumed 

 a high amount of oxygen in 15°/ooS (Fig. 111c). The shrimp accli- 

 mated to 18°C responded much the same in the test salinities as 

 those acclimated to 25°C and tested at 32°C (Fig. 109c). In 2°/ooS 

 the shrimp were hyperactive until death and used more oxygen. In 

 5°/ooS the oxygen consumption was lowest. Significant differences 

 (P=0.01) were present in the metabolic rates between 2°/ooS and 

 other salinities (Table 18), Animals in 15°/ooS responded like those 

 in 25 and SS^/ooS as did the shrimp between 5 and 10°/ooS. However, 

 the respiratory responses both in 5 and 10°/ooS were significantly 

 different (P=0.01) from those in 15, 25, and 36°/ooS. Heavy mortali- 

 ties occurred in 2, 5, 25, and 36°/ooS probably because of the large 

 variation between the acclimation (18°C) and test (32°C) temperatures. 



234 



