Acid-Base Regulation: Interrelationships Between Gaseous and Ionic Exchange

Heisler, N.

doi:10.1007/978-3-642-75380-0_7

Cited by 5 publications

(1 citation statement)

References 80 publications

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“…Water solubility constants and equations for apparent pK (pKapp) were also taken from Boutilier et al (1984); salinity was assumed to be 35 ‰. The solubility constant used for body fluid PCO∑ calculations was 0.48241 mmol l −1 kPa −1 , taken from Heisler (1990) for a body fluid at 8°C with a molarity of 0.55 mol l −1 for dissolved species. The value for pKapp was calculated for a body fluid at 8°C and pH 7.5 with a protein content of 33 g l −1 for coelomic fluid and 132 g l −1 for vascular blood (Terwilliger et al 1980;Childress et al 1984), an ionic strength of non-protein ions of 0.656 mol l −1 for coelomic fluid and 0.630 mol l −1 for vascular blood (Sanders and Childress, 1991) and a Na + concentration of 0.55 mol l −1 (Heisler, 1984(Heisler, , 1990.…”

Section: Methodsmentioning

confidence: 99%

Inorganic Carbon Acquisition by The Hydrothermal Vent Tubeworm Riftia Pachyptila Depends Upon High External And Upon Proton-Equivalent Ion Transport by The Worm

Goffredi

Childress

Desaulniers

et al. 1997

Journal of Experimental Biology

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Riftia pachyptila is the most conspicuous organism living at deep sea hydrothermal vents along the East Pacific Rise. To support its large size and high growth rates, this invertebrate relies exclusively upon internal chemosynthetic bacterial symbionts. The animal must supply inorganic carbon at high rates to the bacteria, which are far removed from the external medium. We found substantial differences in body fluid total inorganic carbon (CO2) both within and between vent sites when comparing freshly captured worms from a variety of places. However, the primary influence on body fluid CO2 was the chemical characteristics of the site from which the worms were collected. Studies on tubeworms, both freshly captured and maintained in captivity, demonstrate that the acquisition of inorganic carbon is apparently limited by the availability of CO2, as opposed to bicarbonate, and thus appears to be accomplished via diffusion of CO2 into the plume, rather than by mediated transport of bicarbonate. The greatly elevated PCO2 measured at the vent sites (up to 12.6 kPa around the tubeworms), which is a result of low environmental pH (as low as 5.6 around the tubeworms), and elevated CO2 (as high as 7.1 mmol l-1 around the tubes) speeds this diffusion. Moreover, despite large and variable amounts of internal CO2, these worms maintain their extracellular fluid pH stable, and alkaline, in comparison with the environment. The maintenance of this alkaline pH acts to concentrate inorganic carbon into extracellular fluids. Exposure to N-ethylmaleimide, a non-specific H+-ATPase inhibitor, appeared to stop this process, resulting in a decline in extracellular pH and CO2. We hypothesize that the worms maintain their extracellular pH by active proton-equivalent ion transport via high concentrations of H+-ATPases. Thus, Riftia pachyptila is able to support its symbionts' large demand for inorganic carbon owing to the elevated PCO2 in the vent environment and because of its ability to control its extracellular pH in the presence of large inward CO2 fluxes.

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