Reese, S. A.*; Crocker, C. E.; Carwile, M. E.; Jackson, D.C.; Ultsch, G.R.: Habitat selection and the physiology of hibernation in common map turtles (Graptemys geographica)

We submerged map turtles (Graptemys geographica) from Wisconsin in water equilibrated with air (normoxic) and in water equilibrated with nitrogen (anoxic) at 3 ^oC. Before submergence and for periods up to 150 days of submergence, plasma PO₂, PCO₂, pH, [Cl^–], [Na⁺], [K⁺], total Mg, total Ca, lactate, glucose, and osmolality were measured; hematocrit and body mass were determined, and plasma [HCO₃^–] was calculated. Turtles in anoxic water developed a severe metabolic acidosis, accumulating lactate from a predive value of 1.7 to 116 mmol/L, associated with a fall in pH from 8.010 to 7.128. Total calcium and magnesium rose from 3.5 and 2.0 to 25.7 and 7.6 mmol/L, respectively, helping to buffer the accumulating lactate. Plasma [HCO₃^–] was titrated from 44.7 to 4.3 mmol/L in anoxic turtles. Only minor disturbances occured in those turtles submerged in normoxic water; there was a marked increase in hematocrit from 31.1 to 51.9%. We suggest that map turtles have an obligatory requirment for a hibernaculum that provides well-oxygenated water and that this requirement is important in determining their distribution.