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Oxygen is essential to all animals because it is one of the main ingredients for energy production in our bodies.When animals respire or bring oxygen into our lungs, our bodies use this oxygen to convert food or glucose to ATP, which runs our bodies. When we have a sufficient amount of oxygen, our bodies respire aerobically and are able to produce 36 ATP for every molecule of oxygen. However, when there is a lack of oxygen due strenuous activity or breath holding, our bodies respire anerobically and can only produce 2 ATP and lactate . Lactic acid build-up in muscles and tissues can be harmful and even deadly (especially in reptiles), so animals have to balance the use of anerobic respiration very carefully in order to operate at efficient levels. (http://eee.uci.edu/courses/bio112/diving.htm)

One easy was to quantitatively measure an animals' metabolic rate or energy production is to measure the amount of oxygen it consumes. However, when respiration rate is used to determine energy production, many different factors such as size, temperature, and activity must be taken into account because they can alter oxygen consumption and energy use. Large animals tend to have lower mass specific metabolic rates than smaller animals, and mammals generally use 10 times more energy than reptiles (Schmidt-Nielsen, 1997). But, because leatherbacks are big bodied reptiles that thermoregulate like mammals, they have a metabolism that breaks the general trend and fits nicely in between the metabolic rates of large reptiles and large mammals. "The resting metabolic rate of leatherbacks are three times those predicted by allometric relationships for green sea turtles and other small reptiles scaled up to leatherback size, but are half of the values predicted for mammals of the same size" (Paladino et al., 1990). Leatherbacks have a lower metabolism than all other homeotherms of the same size becuase their excellent thermoregulatory adaptations allow them to be much more efficient and stay warm without relying on a lot of metabolic energy. Although their metabolism is low compared to other homeotherms, it is quite high compared to other sea turtles, and it allows leatherbacks to be much more active and have a high aerobic capacity (Paladino et al., 1990). Along with oxygen stores and transport, a leatherback's metabolism plays a key role in making them the best and deepest diving sea turtle.

This graph shows a comparison of mass-specific metabolic rates for nesting leatherbacks with other species. The solid black lines represent the minimum metabolic rate necessary to maintain the various temperature gradients shown at the end of the line. These temperature gradients are between the body core and the surface or skin of the animal. Blood flow is assumed to play no part in exchanging heat among the different parts of the animal. Graph from Paladino et al., 1990).