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Leatherback sea turtles are the largest and most widely dispersed of all marine reptiles. They employ a thermoregulatory strategy called gigantothermy, which involves low metabolic rates, the use of large body size, insulation, and counter current heat exchangers, to maintain high core body temperatures under variable and extreme climatic conditions, giving them the

Unlike most of their reptile relatives, leatherbacks are not tied to their environments for the regulation of their metabolism and bodily functions. Leatherback's and other gigantotherms, as the term implies, are characterized by their large body mass and relatively low metabolic rates. Thermoregulation of gigantotherms differs from the thermoregulation of smaller animals because gigantotherms are able to use the physics of their large bodies to help keep them warm. While many animals, especially endotherms, rely on high metabolic rates and heat production to keep them warm, leatherback's and other gigantotherms tend to rely on shear size, which greatly reduces the thermoregulatory demands on their metabolism (Paladino et al., 1990). Large masses have a high thermal inertia and a low surface area to volume ratio, which causes heat exchange between their body core and surroundings to occur very slowly. As opposed to smaller animals, the

Large body size tends to isolate an animal's core from its environment, but leatherback's and other gigantotherms possess some unique thermoregulatory and morphological adaptations that help them reinforce this separation. Equipped with large amounts of insulative peripheral tissues and counter current heat exchangers, leatherback's can easily maintain a high core body temperatre regardless of their surrounding environment (Spotila et al., 1991). Leatherbacks are able to maintain a temperature of about 25 degress Celcius in nearly any aquatic environment. Even in artic waters that are just a few degress above freezing, leatherbacks have no problems stabalizing a core to suface temperature gradient of 18 to 20 degrees Celcius (Frair et al., 1972). Leatherbacks can also use these adaptations on land to keep cool. While nesting female leatherbacks allow their body temperatures to rise to the mid 30's, but to keep from overheating they can change their circulation, which decreases their insulative properties and enables them to stay cool (Paladino et al., 1990). As a result of their large body size and special adaptations, leatherbacks are able to thrive in environments where their relatives cannot, easily making them the most widely dispersed reptile on the face of the planet.

freedomto transverse waters all over the planet. Because leatherbacks and gigantotherms are so reliant on large body size, many scientists hypothesize that dinosaurs may have also used this thermoregulatory strategy because it has proven to be very successful (Paladino et al., 1990).

Although scientists are not sure about the thermoregulatory strategies of dinosaurs, most species of reptile are thermoconformers or ectotherms. This thermoregulatory strategy is very cheap energetically and characterized by low metabolic rates, thus low heat generation. Because they cannot rely extensively on metabolic heat to keep them warm, ectotherms allow thier body temperatures to fluctuate with the temperature of their surroundings. Although this method of thermoregulation is cheap, it comes with many costs because conformers are tied to and dependent on their environment to regulate their metabolic processes. All bodily functions are regulated by metabolic rate, which is in turn controlled by body temperature. If the ambient temperature is not in a range that will produce a metabolic rate that enables a conformer to be active, then they have no choice but to lie in dormancy until their surrounding temperature provides them with a suitable body temperature and metabolic rate so that normal functions can be carried out.

center or core of gigantotherms or large bodies is much farther away from their surface, causing changes that occur on the surface of the animal to be much less of a factor within the body core (Paladino et al., 1990). Smaller animals have less surface area exposed to the surroundings than do larger animals, but becuase their bodies have such a small volume, any temperature change that occurs on the surface is very quickly spread throughout the body. However, the large bodies of gigantotherms along with some unique adaptations, help them to maintain stable internal body temperatures by seperating their core from their environmental conditions.