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Hatchling turtles survive freezing during winter hibernation
K B Storey1, J M Storey, S P Brooks
1Institute of Biochemistry, Carleton University, Ottawa, ON, Canada.
Summary
Painted turtle hatchlings can survive freezing during hibernation, unique among vertebrates. Their bodies naturally produce cryoprotectants like glucose and glycerol to prevent lethal ice damage.
Area of Science:
- Zoology
- Comparative Physiology
- Biochemistry
Background:
- The painted turtle (Chrysemys picta marginata) is the only known reptile capable of natural freeze tolerance.
- Hatchlings hibernate in shallow nests, experiencing sub-zero temperatures and extracellular fluid freezing.
Purpose of the Study:
- Investigate the physiological mechanisms underlying natural freeze tolerance in painted turtle hatchlings.
- Identify potential cryoprotective agents and metabolic responses during freezing.
Main Methods:
- Exposing turtle hatchlings to controlled freezing temperatures (-4°C to -10.9°C).
- Measuring supercooling points and percentage of body water frozen.
- Analyzing concentrations of glucose, glycerol, amino acids, and lactate in blood and organs.
- Assessing glycogen phosphorylase activity and levels of key glycolytic metabolites.
Main Results:
- Hatchlings survived freezing at -4°C (53.4% body water as ice) but not at -10.9°C (67% ice).
- Significant increases in blood glucose (2-3x), blood glycerol (3x), and total blood amino acids (2.25x, mainly taurine) were observed.
- Organs accumulated lactate, indicating reliance on anaerobic glycolysis during freezing.
- Metabolic shifts suggest a dependence on anaerobic glycolysis and cryoprotectant production.
Conclusions:
- Painted turtle hatchlings employ a combination of cryoprotectants (glucose, glycerol, taurine) and metabolic adjustments (anaerobic glycolysis) to survive freezing.
- These findings offer insights into natural freeze tolerance mechanisms with potential applications in mammalian organ cryopreservation.