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

The effects of salinity and temperature on the oxygen-transporting pro perties of the hemolymph of Macrobrachium rosenbergii have been examin ed. Values for Po-2 of the pre- and postbranchial hemolymph (Pao(2) an d Pvo(2)) were quite low (12.7 and 8.4 Torr, respectively) in quiescen t prawns maintained in freshwater. Values for Pao(2) increased signifi cantly, however, in prawns maintained at salinities of 17 parts per th ousand and 28 parts per thousand. Small but significant differences we re recorded in the oxygen affinity (P-50) of hemocyanin from prawns ac climated to salinities of 0 parts per thousand, 17 parts per thousand, and 28 parts per thousand. Salinity had no significant effect, howeve r, on the size of the Bohr effect. In addition, temperature had a pron ounced effect on the P-50 of hemocyanin but did not affect the Bohr va lue; an increase in temperature from 22 degrees to 32 degrees C result ed in an increase in the P-50 of the hemocyanin of prawns maintained i n freshwater from 6.7 to 22.5 Torr (at pH 7.70). Cooperativity was fou nd to be unaffected by either temperature or salinity. Altering the Ca concentration of the hemolymph in vitro had a pronounced effect, howe ver, on P-50; a reduction in [Ca] resulted in an increase in P-50.