high survival rates in high salinities seem to be in agreement with 

 the corresponding burying rates. Abdominal cramps seemed to occur 

 mostly under low temperature and low-salinity conditions. 



Blood Osmoregulation During the Time Course of Adaptation 



Blood osmoconcentration values of P. aztecus from the acclima- 

 tion temperatures 25°, 32°, and 18°C are shown in Figs. 4 to 12. The 

 acclimation salinity was 15°/oo in all cases. In these figures the 

 time intervals are shown on the X-axis and the osmoconcentration 

 levels on the Y-axis. The solid straight line represents the control 

 mean osmoconcentration for the respective test conditions. The sam- 

 ple size, mean, standard error, and standard deviation of each time 

 interval are shown. The means are connected by solid lines. Moving 

 averages are represented by circles and are connected by broken lines. 



In the process of adaptation the responses of the shrimp can be 

 distinguished as immediate response (regulation) , stabilization, and 

 new steady state. The immediate responses sometimes begin with a 

 shock effect, the extent and duration of which varies with the test 

 conditions. The shock effect may result in a sudden loss or sudden 

 gain of blood salts. Changes of this nature were described as under- 

 shooting or overshooting responses, respectively. In this report the 

 immediate regulatory phase covered the physiological responses from 

 the time the animals were transferred to the test conditions until 

 the initial undershoot or overshoot responses were controlled. This 

 phase was followed by stabilization which was characterized by the 

 regulatory fluctuations before the steady-state phase. The usual 

 criterion for a steady state was that the responses between succes- 

 sive time intervals should be more or less similar. If variations 

 did occur they should not be statistically significant. 



56 



