The viability of nearctic freshwater turtles submerged in anoxia and normoxia at 3 and 10 degrees C.

Survival times of temperature-acclimated freshwater turtles submerged in normoxic and anoxic water were determined. Juvenile Chrysemys scripta from Alabama and adult Chrysemys picta bellii from Wisconsin exhibited the maximal survival times of the 10 species and subspecies investigated, both being able to survive at least a half-year of submergence at 3 degrees C in normoxic water. Minimal viability was exhibited by Sternotherus odoratus and Trionyx spiniferus submerged in anoxia at 10 degrees C (5.2 and 2.6 days, respectively). All species lived longer in normoxic water than in anoxic water, attesting to the importance of extrapulmonary gas exchange during submergence at low temperature. While freshwater turtles are often reputed to overwinter buried in mud, which is an anoxic microenvironment, this behaviour seems unlikely for southern Trionyx and Sternotherus, although it may be possible for northern Chrysemys.