Gas transport by hemocyanin-containing blood of the Cephalopod Octopus dofleini

Abstract

O₂ and CO₂ dissociation curves have been obtained for the hemocyanin-containing blood from the large Cephalopod, Octopus dofleini. The oxyhemocyanin curves showed a typical sigmoid shape. Values for T50 and T100 at 11 C and 0.4 mm Hg Pco₂ were 15 and 70 mm Hg Po₂, respectively. The amount of dissolved O₂ in the blood at higher Po₂ was considerable and could reach 10% of the total O₂. The O₂ capacity averaged 3.06 vol %. Dissolved carbon dioxide decreased the affinity of hemocyanin (Hcy) for O₂ (Bohr effect) and reduced the O₂ content at saturation (Root effect). At increased temperature the affinity to oxygen was decreased. The CO₂ dissociation curves showed a moderate CO₂-combining power. A distinct difference in CO₂-combining power between oxygenated and reduced blood was present (Haldane effect). This difference was limited to the physiological range of Pco₂. Increased temperature decreased the CO₂-combining power. The buffering capacity of the blood was low, but in the physiological range of pH there was a distinct difference in buffering ability between reduced and oxygenated blood. The findings are discussed in relation to other marine animals.