The physiology of overwintering in a turtle that occupies multiple habitats, the common snapping turtle (Chelydra serpentina).

Common snapping turtles, Chelydra serpentina (Linnaeus), were submerged in anoxic and normoxic water at 3 degrees C. Periodic blood samples were taken, and PO(2), PCO(2), pH, [Na(+)], [K(+)], [Cl(-)], total Ca, total Mg, [lactate], [glucose], hematocrit, and osmolality were measured; weight gain was determined; and plasma [HCO(3)(-)] was calculated. Submergence in normoxic water caused a decrease in PCO(2) from 10.8 to 6.9 mmHg after 125 d, partially compensating a slight increase in lactate and allowing the turtles to maintain a constant pH. Submergence in anoxic water caused a rapid increase in lactate from 1.8 to 168.1 mmol/L after 100 d. Associated with the increased lactate were decreases in pH from 8.057 to 7.132 and in [HCO(3)(-)] from 51.5 to 4.9 mmol/L and increases in total Ca from 2.0 to 36.6 mmol/L, in total Mg from 1.8 to 12.1 mmol/L, and in [K(+)] from 3.08 to 8.45 mmol/L. We suggest that C. serpentina is tolerant of anoxic submergence and therefore is able to exploit habitats unavailable to some other species in northern latitudes.