CO2 transport in catheterized hydrothermal vent tubeworms, Riftia pachyptila (vestimentifera)

Isolated plumes and vestimenta of the tubeworm Riftia pachyptila were perfused to determine the form in which carbon is transported to the animal's symbionts via the circulatory system. Catheters supplying colored saline were inserted into an afferent blood vessel while samples were collected from the efferent vessel. During perfusion, the plumes were immersed in sea water containing radiolabeled CO2. The effluent showed radioactivity in inorganic carbonate (∑ CO2, sum of all forms), malate, and succinate. When isolated vestimenta were perfused with saline containing labeled CO2, labeled malate and succinate could be detected in the effluent. Carbon transport in the blood as ∑ CO2 is estimated to be of similar importance to that transported after incorporation into organic carbon. The significance for the establishment of the carbon isotope ratio of tubeworms is discussed.