Fig. 3. Metabolic rates (open blue circles) of fishes, cephalopods and crustaceans as a function of minimum depth of occurrence (the depth below which 90% of the individuals in a population are captured). Also shown is the capacity for buffering of intracellular fluids in cephalopods (green circles) and the pH sensitivity of respiratory proteins (red circles) in crustaceans, fishes and cephalopods. Buffering capacity is measured in `slykes', here equal to the quantity of base that must be added to a homogenate made from a 1 g sample of muscle to titrate the pH from approximately 6 to 7. The Bohr coefficient is the change in the log of respiratory oxygen affinity (P₅₀; defined as the oxygen partial pressure at which the respiratory protein is half-saturated) over the change in pH. Bohr coefficients in these animal groups are negative but are presented here as absolute values. The metabolic rates are normalized to a common body mass of 10 g and measurement temperature of 5°C using measured scaling coefficients and Q₁₀ values where available or assuming a scaling coefficient of -0.25 and a Q₁₀ of 2. Data are from Childress and Seibel (1998) and references therein. Note that the y-axis is a log scale.

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