A poikilotherm is an organism whose internal temperature varies considerably.

It is comparatively easy for a poikilotherm to accumulate enough energy to reproduce.

This is the minimum annual temperature range that a poikilotherm as large as Titanoboa could live.

A rare exception, the naked mole rat, produces little metabolic heat, so it is considered an operational poikilotherm.

Chromatophore (the pigment cell type found in poikilotherm animals)

Therefore, the great white shark can be considered an endothermic poikilotherm because its body temperature is not constant but is internally regulated.

The correct scientific word for cold-blooded is poikilotherm (noun), poikilothermic (adjective).

It is this distinction that often makes the term "poikilotherm" more useful than the vernacular "cold-blooded", which is sometimes used to refer to ectotherms more generally.

For instance, endothermic animals maintain a constant body temperature, while exothermic (both ectotherm and poikilotherm) animals exhibit wide body temperature variation.

The lower proline and hydroxproline contents of cold-water fish and other poikilotherm animals leads to their collagen having a lower thermal stability than mammalian collagen.

Their poikilotherm metabolism has very low energy requirements, allowing large reptiles like crocodiles and the large constrictors to live from a single large meal for months, digesting it slowly.

The theory proposed that isochore's composition varied markedly between "warm-blooded" (homeotherm) vertebrates and "cold-blooded" (poikilotherm) vertebrates and later became known as the isochore theory.

Because their metabolism is variable and generally below that of homeothermic animals, sustained high-energy activities like powered flight in large animals or maintaining a large brain is generally beyond poikilotherm animals.

A poikilotherm must either operate well below optimum efficiency most of the time, migrate, hibernate or expend extra resources producing a wider range of enzymes to cover the wider range of body temperatures.

Differences in feeding, and locomotion, rates between summer and winter reflect the fact that the crown-of-thorns like all marine invertebrates is a poikilotherm whose body temperature and metabolic rate are directly affected by the temperature of the surrounding water.