acclimated at 21°C regulated relatively better in 17.0°/ooS than in 

 8.5°/ooS. At 26°C and 31°C the regulation was comparatively more 

 efficient throughout the salinity range. 



Osmoregulation is a capacity found in all estuarine animals. 

 On the basis of chloride ion concentration, which normally comprises 

 about 50% of the total blood osmoconcentration, the euryhaline brown 

 shrimp exhibited hyperosmotic regulation in low salinities (8.5 and 

 17.0°/oo), hyposmotic regulation in high salinities (25.5 and 34.0°/oo) 

 and isosmotic with 17°/ooS or slightly above. Osmoregulation is sub- 

 jected to temperature influence similar to ion regulation. 



In our previous studies on salinity tolerance brown shrimp were 

 acclimated to 8.5, 17.0, 25.5, and 34.0°/ooS. The organisms were 

 found to take advantage of the acclimation by expanding their salinity 

 tolerance range into the media adjacent to that of the acclimation. 

 For instance, acclimation to 8.5°/ooS helped them to penetrate to a 

 lower salinity of 3.4°/oo without any mortality. Normally in a 

 direct transfer from 17°/ooS about 50% of the shrimp died in 3.4°/ooS. 

 Shrimp acclimated to 34.0°/ooS had similar advantages of penetrating 

 a higher concentration of 42.5''/ooS without any apparent ill effects. 

 In the same fashion the shrimp acclimated to 21°C survived in greater 

 numbers and in a wider salinity range when tested at 21°C than in 

 31 °C. The animals acclimated to 31 °C suffered the same disadvantage 

 at 21°C; but the effect was lesser than that experienced by those 

 acclimated at 21°C and tested at 31°C. The animals acclimated at 

 31°C survived better at 26°C than at 31°C (Venkataramiah et al. 1974). 



Therefore, acclimation seems to be a physiological phenomenon 

 that permits the organisms to compensate for alternatives in the 

 environmental variables. Such compensations promote an increased 

 capacity to survive in an unfavorable environment. Regulation is 

 presumably a faster process than acclimation, resulting from routine 



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