Unusual carbon dioxide-combining properties of body fluids in the hydrothermal vent tubeworm Riftia pachyptila
- 作者：Toulmond ; A.
- 刊名：Oceanographic Literature Review
- 出版年：1995
- 期刊代码：64_09670653
- 类别：ear
- 出版时间：May, 1995
- 卷：42
- 期：5
- 页码：350
- 文件大小：105 K
摘要
Total CO2 (∑CO2) up to 50 mmoll−1, corresponding to internal CO2 partial pressures (PCO2) up to 6 kPa (1 kPa 
7.5 mm Hg or Torr), have been measured in the body fluids of the Riftia pachyptila (Jones) sampled at 13°N on the East Pacific Rise. At physiological pH values, such high ∑CO2 and PCO2 are quite unusual in water-breathing animals. Gel filtration analysis of the fluids revealed that the protein-free fractions retained most of the CO2: about 64%in blood and 80%in coelomic fluid. This corresponds to a base excess of unknown nature and origin at a concentration up to 30 meq 1−1. The nutritional needs of the mouthless and gutless Riftia are totally derived from the metabolic activity of sulphide-oxidizing, chemolithoautotrophic bacterial symbionts. In an external environment in which PCO2 varies widely due to the turbulent mixing of the hot, sulphide- and CO2-rich vent water with the cold, CO2-poor deep sea water, it is proposed that the base excess has three main functions: first, to retain CO2 in the body fluids when the external PCO2 is low; second, to act as a buffer when external PCO2 is high; third, to allow the large coelomic compartment to act as a CO2 store, thus permitting the symbiotic bacteria to fix carbon continuously even when the external supply of carbon dioxide fluctuates.
7.5 mm Hg or Torr), have been measured in the body fluids of the Riftia pachyptila (Jones) sampled at 13°N on the East Pacific Rise. At physiological pH values, such high ∑CO2 and PCO2 are quite unusual in water-breathing animals. Gel filtration analysis of the fluids revealed that the protein-free fractions retained most of the CO2: about 64%in blood and 80%in coelomic fluid. This corresponds to a base excess of unknown nature and origin at a concentration up to 30 meq 1−1. The nutritional needs of the mouthless and gutless Riftia are totally derived from the metabolic activity of sulphide-oxidizing, chemolithoautotrophic bacterial symbionts. In an external environment in which PCO2 varies widely due to the turbulent mixing of the hot, sulphide- and CO2-rich vent water with the cold, CO2-poor deep sea water, it is proposed that the base excess has three main functions: first, to retain CO2 in the body fluids when the external PCO2 is low; second, to act as a buffer when external PCO2 is high; third, to allow the large coelomic compartment to act as a CO2 store, thus permitting the symbiotic bacteria to fix carbon continuously even when the external supply of carbon dioxide fluctuates.