Figure 3. A pH/HCO₃⁻/CO₂ diagram of pHe compensation in Pacific hagfish during exposure to 10 (•[blue]), 30 (▼[yellow]) and 50 (■[red]) mm Hg pCO₂.

Values are means ± SEM. Curved long-dashed lines represent pCO₂ isopleths and the short-dashed line represents the blood buffer line (5 mM [HCO₃⁻] pH⁻¹ blood). Data labels represent duration of CO₂ exposure (h). Shaded area represents the “bicarbonate concentration threshold” associated with pHe compensatory limits in other fish as described previously²⁰.