Effect of 25°C acclimation on osmoregulation 



In shrimp acclimated to and tested at 25 °C the immediate shock 

 effects were observed in all salinities other than in control 15°/ooS 

 (Fig. 4) . The shock effect was observed both in behavior and in the 

 blood osmoregulation. In salinities lower than 15°/ooS the shrimp 

 lost salts to the external media (efflux] . In higher salinities the 

 animals gained salts from the media (influx) . In test salinities 

 adjacent to 15°/ooS immediate responses were exhibited for only a 

 brief period of about two hours. In extreme concentrations of 2°/oo 

 and 36°/ooS the initial responses were prolonged for about four to 

 six hours. Usually the greatest changes in the blood concentration 

 occurred during the immediate regulation phase. 



The initial osmoregulatory pattern in shrimp acclimated to 25°C 

 and tested in 32°C (Fig. 5) or in 18°C (Fig. 6) was similar to those 

 tested at 25°C in the respective salinities. One difference, how- 

 ever, was that the salt loss or gain occurred longer in 18° or 32°C 

 than in 25°C. Another difference was that the shrimp lost salts even 

 in the control salinity 15°/oo because of their experiencing a tem- 

 perature change from acclimation. Between the two test temperatures, 

 the changes continued longer in 18°C than in 32°C. At 18°C the rapid 

 salt exchange transpired for two hours in 15°/ooS, four hours in 

 25°/ooS and from 16 to 24 hours in the other salinities (Fig. 6) 

 while at 32°C rapid salt exchange ceased after two to four hours 

 (Fig. 5). 



Stabilization of the blood osmoregulation at 25°C started within 

 two to six hours, and a new steady state was reached between the 

 fourth and seventh day in all salinities. On the basis of moving 

 averages the steady-state levels appeared even earlier, by the sec- 

 ond day in 5, 25, and 36°/ooS. The wide fluctuations in standard 

 deviation values at 2, 5, and 36°/ooS (Fig. 4) reflect the individual 

 osmoregulatory variations. The new steady-state levels were main- 

 tained at higher levels in 25 and 36°/ooS than in 15°/ooS and lower 

 in 2, 5, and 10°/ooS. 



66 



