We examined hemolymph pH, total CO_2 content (Tco_2), CO_2 partial pressure (Pco_2) and bicarbonate concentration ([HCO_3^-]) in order to evaluate the acid-base balance of the hard-shelled mussel Mytilus coruscus in normoxic conditions. The hemolymph was collected anaerobically through a cannula by pretreatment of the adductor muscle by catheterization. The mean values of the hemolymph pH and Tco_2 were 7.617 and 1.44 mM/l, respectively. The CO_2 solubility coefficient (αco_2) was 40.6 μM/l/mmHg. The apparent dissociation constant of carbonic acid (pKapp) was able to be expressed using the estimated equation as follows: pKapp = - 6371.321 + 3923.163 ・ pH - 856.100 ・ pH^2 + 82.978 ・ pH^3 - 3.014 ・ pH^4. Using αco_2 and pKapp determined in this study, hemolymph Pco_2 and [HCO_3^-] were calculated as 0.57 mmHg and 1.42 mM/l, respectively. The non-bicarbonate buffer value (β_NB) was 0.44 Slykes.
Mytilus coruscus
acid-base balance
cannulation
dissociation constant of carbonic acid
CO_2 partial pressure
hemolymph