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 a nimal's symbionts via the circulatory system. Catheters supplying colo red saline were inserted into an afferent blood vessel while samples w ere collected from the efferent vessel. During perfusion, the plumes w ere immersed in sea water containing radiolabeled CO2. The effluent sh owed radioactivity in inorganic carbonate (Sigma CO2, sum of all forms ), malate, and succinate. When isolated vestimenta were perfused with saline containing labeled CO2, labeled malate and succinate could be d etected in the effluent. Carbon transport in the blood as Sigma CO2 is estimated to be of similar importance to that transported after incor poration into organic carbon. The significance for the establishment o f the carbon isotope ratio of tubeworms is discussed. (C) 1995 Wiley-L iss, Inc.