II: MATERIALS AND METHODS 



Experimental Design 



The time course of adaptation in brown shrimp, Penaeus aztecus , 

 was studied by analyses of physiological responses to salinity and 

 temperature variations. Respiratory rates and blood osmotic and 

 ionic regulation were used as physiological parameters. Brown shrimp 

 were acclimated for one week to either 25°C (laboratory temperature), 

 IS^C or to 32°C in a control salinity of 15°/oo. The animals were 

 then directly transferred to salinities 2, 5, 10, 15 (control), 25, 

 and 36°/oo for adaptation in combination with 18°, 25°, and 32°C. The 

 test salinities and temperatures approximate the ranges of spring and 

 summer estuarine conditions. Respiratory rates were measured at in- 

 tervals of 0, 1, 2, 4, 6, 10, 24, 48, 72, 96, 120, 144, and 168 hours. 

 Blood sampling was conducted at the same intervals except for addi- 

 tion of a 16-hour sample and ommission of the 120- and 144-hour samples. 

 It was presumed that in the process of adaptation the major physiolog- 

 ical changes would take place within one week (168 hours). Males and 

 females were tested separately to determine the effect of sex on the 

 physiological responses. 



Experimental Animals 



Juvenile brown shrimp ranging from 85 to 100 mm total length 

 were obtained from local bayous or bays and from bait shrimp dealers. 

 The animals were collected from waters at a salinity range of 10 to 

 20°/oo. Although the shrimp occurred in a 14° to 30°C range, most 

 were taken from 23° to 29°C. The animals were transported from the 

 collection area to the laboratory in 20-gallon (75.7 L) styrofoam 

 ice chests and provided with continuous oxygen. The use of pure 

 oxygen during transport seemed to help the animals have a fast recovery 

 from trawling stress as well as from the overcrowding effect in the 

 bait tanks. 



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