The oxygen and acid-base status of hemolymph in winged pearl oyster Pteria penguin under the normoxic condition

We examined hemolymph O_2 partial pressure (Po_2), pH, total CO_2 concentration (Tco_2), CO_2 partial pressure (Pco_2), and bicarbonate concentration ([HCO_3^–]) to evaluate the acid–base balance of the winged pearl oyster Pteria penguin under normoxic condition. Hemolymph was collected anaerobically from the adductor muscle. Mean values for hemolymph Po_2, pH and Tco_2 were 73.4 torr, 7.598 and 2.40 mM/L, respectively. Hemolymph Pco_2 was calculated using the rearranged Henderson–Hasselbalch equation, yielding 1.83 torr and a [HCO_3^–] of 2.33 mM/L. The non-bicarbonate buffer value (hemolymph pH–[HCO_3^–] relational expression slope) was 1.99 slykes, higher than that of other marine bivalves. Thus, the winged pearl oyster hemolymph has a comparatively greater nonbicarbonate buffering capacity.