INFLUENCE OF TEMPERATURE AND SALINITY ON THE YELLOWLEG SHRIMP, PENAEUS-CALIFORNIENSIS HOLMES, PROPHENOLOXIDASE SYSTEM

The effects of salinity and temperature on plasma protein concentratio n and total haemocytic prophenoloxidase (proPO) were determined. Group s of 10 juvenile yellowleg shrimp, Penaeus californiensis Holmes, were acclimated for 20 days at different salinities (28 parts per thousand , 32 parts per thousand, 36 parts per thousand, 40 parts per thousand and 44 parts per thousand at 25 degrees C) or temperatures (18, 22, 25 , 28 and 32 degrees C at 36 parts per thousand). While total protein l evels were not affected, the quantities of proPO increased as salinity was elevated, Temperature affected both haemolymph parameters, showin g a significant decrease in proPO at 32 degrees C, and an increase of protein at 28 and 32 degrees C. These results may help to explain the elevated disease susceptibility of shrimp at higher salinities and/or temperatures.