time two more shrimp were stressed. The remaining shrimp were quiet 

 but occasionally swam around. 



Effect of Acclimation to Media with Deviated Ions 

 on Tolerance in Extreme Salinity and Temperature 



Brown shrimp were acclimated at 25°C to 5 and 10°/ooS in which 

 the normal concentration of cations was changed as described in the 

 material and methods. It was found that large numbers of brown shrimp 

 did not survive in the deviated media over a long period. Mortalities 

 in the acclimation process increased from 50 to 100% in certain com- 

 binations. Very few shrimp survived acclimation to 10°/ooS with 40% K 

 and 6% Mg. In 5°/ooS with 40% K concentration few animals survived. 

 Therefore, the availability of acclimated animals became a limiting 

 factor in performing the tests. 



Tlie surviving shrimp were tested in 2.5 and 42.5°/ooS at 18° 

 and 32°C combinations. Survival of shrimp in these tests was very 

 low (Table 28). Shrimp tranferred from any of the acclimation salin- 

 ities to 42.5°/ooS did not survive at either temperature. The shrimp 

 died sooner at 32°C than at 18°C. At 32°C the shrimp were hyper- 

 active for 10 to 30 minutes. Some showed signs of stress, lying on 

 their sides and beating the pleopods feebly. Others were depressed. 

 Some survived for 12 to 18 hours but most of the shrimp died within 

 one to five hours. At 18 °C the shrimp were quiet from the beginning 

 and became depressed (or stressed) within two hours. Deaths occurred 

 between five and 20 hours. The surviving three animals after 24 

 hours were severely stressed and could not have lived much longer. 



Almost all shrimp acclimated to 10°/ooS were dead in 2.5°/ooS 

 at both temperatures. Only one shrimp from the 15% Ca medium sur- 

 vived at 32°C. The animal was, however, inactive. Some shrimp 

 acclimated to deviated ion media in 5°/ooS survived in 2.5°/ooS, 



264 



