degree of osmotic independence was limited at 18°C to a narrower sa- 

 linity range than in 25°C. At 25°C the salinity adaptation was 

 faster than in the other temperatures; the rate of overall mortality 

 due to salinity change was lower. The range of salinities to which 

 the shrimp can be adapted by direct transfer was wider than in 18° 

 or 32°C. This is possible in Penaeus aztecus because of its geo- 

 graphic distribution which is confined to tropical and subtropical 

 waters. 



296 



