acclimation to the 10°/ooS with 40% K or 6% Mg concentrations; so 

 testing of shrimp from those backgrounds could not be done. Too 

 few shrimp survived in 5°/ooS with 40% K concentration to test at 

 both 18° and 32°C; therefore, tests were omitted at 18°C. The tests 

 on shrimp from the other deviated ion backgrounds were conducted 

 using as many experimental animals as possible from among the sur- 

 vivers of acclimation. 



Blood Sampling 



Blood samples were taken from the test shrimp at intervals 

 described previously and analyzed for total osmotic concentration 

 and for chloride, potassium, magnesium, and calcium. The shrimp 

 were sacrificed during the sampling operation. Water samples were 

 taken at the start of each test. Since blood sampling was done at 

 close intervals it was always difficult to select animals of the 

 same size range in each condition. The fact that shrimp were 

 sampled by sex made it more impracticable. In order to overcome 

 these problems 6 to 10 animals of the same sex were initially sorted 

 out into perforated plastic boxes. The boxes were transferred into 

 the test tanks (250 gallon capacity) and retrieved at set intervals. 

 Before sampling each shrimp was wiped with a towel moistened in de- 

 ionized water to remove external salt and then dried with tissue 

 paper. Blood was taken directly from the heart and from the ventral 

 sinus. Dispo Pipets (American Hospital Supplies) with sharply ta- 

 pered ends (1 mm diameter) were used to collect the blood. Care was 

 taken to prevent puncturing the hepatopancreas. Normal samples were 

 light to dark blue in color but those with contamination were dis- 

 colored. Such samples were discarded. The samples that were rela- 

 tively transparent were also discarded since such samples apparent- 

 ly came from freshly molted shrimp. 



Each sample consisted of blood pooled from two to four shrimp 

 of the same sex. More animals from 32 °C acclimation were needed for 



40 



