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Hibernating without Oxygen: Physiological Adaptations of the Painted Turtle
Author(s) -
Jackson Donald C.
Publication year - 2002
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2002.024729
Subject(s) - anoxic waters , lactic acid , turtle (robot) , glycolysis , substrate (aquarium) , biophysics , oxygen , biology , oxidative phosphorylation , chemistry , ecology , metabolism , microbiology and biotechnology , zoology , biochemistry , paleontology , organic chemistry , bacteria
Many freshwater turtles in temperate climates may experience winter periods trapped under ice unable to breathe, in anoxic mud, or in water depleted of O 2 . To survive, these animals must not only retain function while anoxic, but they must do so for extended periods of time. Two general physiological adaptive responses appear to underlie this capacity for long‐term survival. The first is a coordinated depression of metabolic processes within the cells, both the glycolytic pathway that produces ATP and the cellular processes, such as ion pumping, that consume ATP. As a result, both the rate of substrate depletion and the rate of lactic acid production are slowed greatly. The second is an exploitation of the extensive buffering capacity of the turtle's shell and skeleton to neutralize the large amount of lactic acid that eventually accumulates. Two separate shell mechanisms are involved: release of carbonate buffers from the shell and uptake of lactic acid into the shell where it is buffered and sequestered. Together, the metabolic and buffering mechanisms permit animals to survive for 3–4 months at 3 °C with no O 2 and with circulating lactate levels of 150 mmol l −1 or more.