Long-Term Submergence at 3 °C of the Turtle, Chrysemys Picta Bellii, in Normoxic and Severely Hypoxic Water

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Abstract
Survival and blood acid-base status were measured on freshwater turtles (Chrysemys picta bellii Gray) that were submerged at 3 °C in either aerated (high O2) or N2-equilibrated (low O2) water. Results from catheterized turtles, without access to air under these conditions, and from non-catheterized turtles which were either apnoeic (in high O2 and low O2 water) or in high O2 water with access to air, are compared. Under the most adverse conditions (catheterized, submerged, low O2), survival duration was 126±14 (X±S.E.) days, and 2 of the 10 turtles so treated were still alive after 177 days, although their condition was poor. Apnoeic, high O2 turtles generally survived longer and were in better condition despite a skin fungus condition that selectively affected these animals. Six of ten non-catheterized high O2 turtles were still alive after 189 days without breathing. All apnoeic turtles developed an acidosis which, except for a transient hypercapnia in low O2 turtles, was a metabolic acidosis attributable to elevated lactic acid. Acidosis was most severe in low O2 turtles in which peak plasma lactates exceeded 200 mM. High O2 turtles, as judged by higher blood PO2 and lower lactate concentrations, were able to extract dissolved O2 from the water and support a significant portion of their metabolic requirements by aerobic metabolism. Our data indicate that wintering turtles can remain alive for up to 6 months, even while totally anoxic and severely acidotic, but that the acid-base state and probably the recovery potential are significantly improved if dissolved O2 is available for extrapulmonary uptake.