TEMPERATURE AND SALINITY EFFECTS ON OXYGEN-TRANSPORT BY THE HEMOLYMPH OF THE FRESH-WATER PRAWN MACROBRACHIUM-ROSENBERGII (DE MAN)

The effects of salinity and temperature on the oxygen-transporting properties of the hemolymph of Macrobrachium rosenbergii have been examined. Values for Po-2 of the pre- and postbranchial hemolymph (Pao(2) and Pvo(2)) were quite low (12.7 and 8.4 Torr, respectively) in quiescent prawns maintained in freshwater. Values for Pao(2) increased significantly, however, in prawns maintained at salinities of 17 parts per thousand and 28 parts per thousand. Small but significant differences were recorded in the oxygen affinity (P-50) of hemocyanin from prawns acclimated to salinities of 0 parts per thousand, 17 parts per thousand, and 28 parts per thousand. Salinity had no significant effect, however, on the size of the Bohr effect. In addition, temperature had a pronounced effect on the P-50 of hemocyanin but did not affect the Bohr value; an increase in temperature from 22 degrees to 32 degrees C resulted in an increase in the P-50 of the hemocyanin of prawns maintained in freshwater from 6.7 to 22.5 Torr (at pH 7.70). Cooperativity was found to be unaffected by either temperature or salinity. Altering the Ca concentration of the hemolymph in vitro had a pronounced effect, however, on P-50; a reduction in [Ca] resulted in an increase in P-50.