Any so-called cold-blooded animal; that is, any animal whose regulation of body temperature depends on external sources, such as sunlight or a heated rock surface. The ectotherms include the fishes, amphibians, reptiles, and invertebrates. The body temperatures of aquatic ectotherms are usually very close to those of the water. Ectotherms do not require as much food as warm-blooded animals (endotherms) of the same size, but most cannot deal as well with cold surroundings.
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