Long-term submergence at 3 degrees C of the turtle Chrysemys picta bellii in normoxic and severely hypoxic water. III. Effects of changes in ambient and subsequent air breathing

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Abstract
Western Painted Turtles, Chrysemys picta bellii (N = 5), were maintained submerged and apneic for 90 days: days 0–21 in severely hypoxic water ( = 0–5 mmHg), days 22–43 aerated water ( ∼ 160 mmHg), and days 44–90 again in hypoxic water. From day 90 onward, the water was aerated and the turtles were allowed access to the air ; water and air temperatures were maintained at 3 °C. Arterial blood samples were taken periodically and analysed for , pH, [Na+], [K+], [Cl−], [lactate−], [glucose] and haematocrit. Plasma [HCO3−] was calculated for all samples and total plasma calcium was measured on samples from two animals. Each exposure to low water caused progressive lactic acidosis and a transient respiratory acidosis with an accompanying fall in plasma [Cl−] and rise in plasma [K+] and [calcium]. During the intervening period in aerated water, blood pH recovered significantly (from 7·33 to 7·74 in 7 days), due primarily to a fall in , (from 233 to 10·6 mmHg), while [lactate−] remained unchanged (at about 50 mM), and [HCO3−] rose slightly. Plasma [K+] promptly returned to nearly normal values. When permitted to breathe on day 90, the three surviving turtles rapidly restored pH to normal by pronounced hyperventilation ( < 5 mmHg). Metabolic acidosis, however, disappeared slowly with a for [lactate−] and [HCO3−] restoration of about 2 weeks. We conclude that a wintering turtle can stabilize or even slightly improve its acid-base and ionic status by moving from an anoxic environment to well-oxygenated water. Further improvement can be gained by breathing air, but recovery proceeds at a very slow rate if the animal remains at 3 °C.