Poikilotherm

Part of speech: noun

Definitions

1. A creature that depends on external temperatures for its thermal regulation, unable to maintain a stable internal body heat
2. An organism that changes its body heat based on the surrounding environment, lacking independent thermal control
3. An animal that adjusts its internal temperature according to external conditions rather than generating heat internally

Etymology: Poikilotherm is built from two Greek elements. "Poikilos" meant "dappled," "variegated," or "many-coloured," and it is the same root behind the "poikilo-" in words describing mottled or irregular patterns. "Therme" meant "heat," the source of English "thermal" and "thermometer." Put together, the word describes an animal whose body temperature is not generated internally but varies with its surroundings. The sense of "dappled" in the first element is the surprising part. Nothing about the word's parts points directly to temperature regulation; the "many-coloured" meaning of "poikilos" carries no thermal sense at all. The compound is a scientific coinage assembled from classical Greek pieces, so it reflects the vocabulary of modern biology rather than any ancient usage. Its meaning rests entirely on the second element, "-therm," which marks the animal's relation to heat. The word is used for what is more commonly called a cold-blooded animal. Its pattern of formation, combining a Greek adjective with "-therm," follows the same method as other technical terms in biology and physiology.

Synonyms: cold-blooded animal, ectotherm, reptile, amphibian, fish

Antonyms: homeotherm, warm-blooded