Fig. 1. (A) Plot of H₂S uptake (µmol g^-1 h^-1) as a function of H₂S (µmol l^-1) by Riftia pachyptila maintained in high-pressure aquaria at pH 5.66. (B) Plot of H₂S uptake (µmol g^-1 h^-1) as a function of HS^- (µmol l^-1) by Riftia pachyptila maintained in high-pressure aquaria at pH 7.48. All other substrates were held at `typical' concentrations (see Materials and methods). All rates are expressed in terms of wet mass.