How can ectotherms regulate their temperature

These mitochondria enables them to generate heat by increasing the rate at which they metabolize fats and sugars. However, endothermic animals must sustain their higher metabolism by eating more food more often. For example, a mouse endotherm must consume food every day to sustain high its metabolism, while a snake ectotherm may only eat once a month because its metabolism is much lower.

A poikilotherm is an organism whose internal temperature varies considerably. It is the opposite of a homeotherm, an organism which maintains thermal homeostasis. Poikilothermic animals include many species of fish, amphibians, and reptiles, as well as birds and mammals that lower their metabolism and body temperature as part of hibernation or torpor.

Some ectotherms can also be homeotherms. For example, some species of tropical fish inhabit coral reefs that have such stable ambient temperatures that their internal temperature remains constant. Heat can be exchanged between an animal and its environment through four mechanisms: radiation, evaporation, convection, and conduction.

Heat radiates from the sun and from dry skin the same manner. When a mammal sweats, evaporation removes heat from a surface with a liquid. Convection currents of air remove heat from the surface of dry skin as the air passes over it. This term is misleading, however, because many lizards have high body temperatures. External temperature plays a major role in the activity rate of ectothermic animals. When the weather is warm, they become active. They slow down when the temperature drops.

Certain ectotherm behaviors help regulate body temperature. To warm up, reptiles find sunny places, and stretch out for maximum exposure. If it gets too warm, lizards alternate between sun and shade. Amphibians warm up by moving into the sun or diving into warm water.

Once heat is generated, its use for thermoregulatory purposes will be optimized by diminishing heat dissipation to the environment. In this regard, endothermic vertebrates are endowed with effective insulation, hairs and feathers, to prevent heat loss.

Ectothermic vertebrates, on the other hand, clearly lack such features. However, heat loss to the environment can be decreased by the possession of larger body sizes that increase thermal inertia. This strategy is illustrated by leatherback turtles, Dermochelys coriacea , whose gigantic body size associated with relatively high rates of muscle metabolism allows for the maintenance of body temperature much warmer than the cold waters used for foraging.

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