We collected the hemolymph anaerobically through a cannula inserted into the adductor muscle of Akoya pearl oyster Pinctada fucata martensii submerged in experimental seawater, and examined hemolymph pH, total CO_2 concentration (Tco_2), CO_2 partial pressure (Pco_2), and bicarbonate concentration ([HCO_3^–]) in order to evaluate the ability of the acid–base balance of P. fucata martensii in normoxic conditions. The mean values of hemolymph pH and Tco_2 were 7.544 and 2.21 mM/L, respectively. The apparent dissociation constant of carbonic acid (pKapp) was estimated using the following equation： pKapp = 225.712 – 97.096 • pH + 14.313 • pH^2 – 0.7035 • pH^3. Using mean values of pKapp (5.99585) and CO_2 solubility coefficient (αco_2, 37.02 µM/L/torr) determined in this study, the hemolymph Pco_2 and [HCO_3^–] were calculated as 1.69 torr and 2.14 mM/L, respectively. The non-bicarbonate buffer value (ꞵ_NB) was 0.967 slykes.
Pinctada fucata martensii
Akoya pearl oyster
hemolymph
acid-base balance
adductor muscle
buffer value