... exposure to 13 kPa PCO2, 9 kPa PO2 in common snapping turtles or 1 h exposure to 6.5 kPa arterial PCO2 in western painted turtles. A value ≥0 is indicative of preferential pHi regulation. Bars for pHe are hatched. The only simultaneous measurements of pH e and pH i that have been made in later...