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Counter-current Heat Exchange

a diagram of heat flow in a turtle's flipper

Reptiles are ectothermic, meaning they rely on the environment to regulate their body temperature, and sea turtles are no exception. It is therefore surprising that unlike other sea turtles, leatherbacks are cold-adapted. They can migrate to cold water to hunt their prey without getting cold-stunned. The leatherback achieves this feat with counter-current heat exchange. This system runs warm blood from their inner bodies out to their extremities next to the cold blood running back inwards. The two blood temperatures participate in heat exchange and, therefore, the cold blood is warmed before re-entering the body core. 

Tags: Sea turtles