We examined hemolymph pH, total CO_2 content（Tco_2, mM/l), CO_2 partial pressure（Pco_2, mmHg）and bicarbonate concentration（[HCO_3^-], mM/l) in order to evaluate the acid-base balance of the black-lip pearl oyster Pinctada margaritifera under normoxic conditions. Hemolymph was collected anaerobically through a cannula after catheterization of the adductor muscle. The mean values of the hemolymph pH and Tco_2 were 7.563 and 2.04 mM/l, respectively. Using the CO_2 solubility coefficient and apparent dissociation constant of carbonic acid determined in this study, Pco_2 and [HCO_3^-] were calculated as 1.50 mmHg and 1.98 mM/l, respectively. These values were in same range as those of the hemolymph of the akoya pearl oyster P. fucata.
Pinctada margaritifera
cannulation
hemolymph
acid-base balance
Pco_2
dissociation constant of carbonic acid