six hours. However, salinity adaptation seemed to be complete in 

 5 to 25°/ooS within the one week period. While judging the adaptive 

 state in 2 and 36°/ooS the mortality rates should not be ignored. 

 The high mortalities indicate that adaptation to these extreme sa- 

 linities is difficult in a direct transfer from 15°/ooS and 25°C. 

 The adaptation process was further complicated by a simultaneous 

 temperature change. Adaptation to these extreme salinities should 

 be made easier by a gradual change of the salinity and temperature 

 factors. Despite the gradual change, when salinity and temperature 

 factors are involved simultaneously, the salinity adaptation ob- 

 viously becomes slower than in normal temperature conditions. 



In shrimp acclimated and tested in 18°C salinity adaptation 

 seemed to occur fast within the 10 to 36°/ooS range. Within two 

 days there was a total mortality of shrimp used in metabolic studies 

 in 2°/ooS and a high mortality in 5°/ooS. In other salinities there 

 were no mortalities other than those in molting. With the exception 

 of 2°/ooS, steady-state levels were achieved in metabolic and os- 

 motic or ionic regulation in all salinities within six hours. In 2 

 and 5°/ooS although major osmotic changes were completed within six 

 hours, steady-state levels were not seen until the fourth day. By 

 acclimation to 18°C the survival and rate of adaptation were improved 

 at 18°C test temperature in 10, 15, 25, and 36°/ooS but not in 2 or 

 5°/ooS. Low-salinity and low temperature combinations impaired the 

 rate of salinity adaptation in brown shrimp. Similar findings were 

 made in our previous studies (Venkataramiah et al. 1974). It also 

 fits previous field observations showing that penaeid shrimp leave 

 the cool, low-salinity bays in winter (Gunter 1950). 



The shrimp acclimated to 18°C and used in the respiratory 

 studies at 25°C experienced a high mortality in 2 and 5°/ooS. 

 Stabilization in the metabolic rates and steady-state levels 

 occurred in 10, 15, and 25°/ooS within the first day and in 2, 



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