Poikilotherm

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Related to poikilothermic: homeothermic, poikilothermia

poikilotherm

[pȯi′kil·ə‚thərm]
(zoology)
An animal, such as reptiles, fishes, and invertebrates, whose body temperature varies with and is usually higher than the temperature of the environment; a cold-blooded animal.

Poikilotherm

 

a cold-blooded animal, that is, an animal with a variable body temperature that changes as a function of the temperature of the environment. Poikilotherms include all invertebrates; the only poikilothermic vertebrates are fishes, amphibians, and reptiles.

The body temperature of poikilotherms is generally only 1° or 2° higher than, or equal to, that of the environment. Thermoregulation is imperfect. In many poikilotherms the body temperature rises as a result of muscular work or the absorption of solar heat. For example, the body temperature of bumblebees in flight may reach 38° or even 44°C at an air temperature of 4° to 8°C. However, after the cessation of flight the body cools rapidly to the temperature of the environment. If the external temperature rises above or falls below optimal limits, poikilotherms become torpid or perish. Many of them are in torpor a large part of the year; for example, the turtle Testudo horsfieldi is active only three months of the year. The absence of perfect thermoregulatory mechanisms in poikilotherms may be explained by the relatively poor development of their nervous systems (especially the central nervous system), a level of metabolism approximately 20 to 30 times lower than that of homeo-therms, and other features associated with the fact that poikilotherms have a more primitive organization than birds and mammals.

References in periodicals archive ?
(a) fish are poikilothermic; (b) fish body weight is supported by water; (c) fish excrete nitrogenous waste as ammonia.
We all live in a world run by cryptorchid, poikilothermic decerebrates, but if you read this column regularly you need never feel alone again.
Being poikilothermic organisms, the development, reproduction and predatory potential of insects is affected to a great extent by temperature variations in the environment.
The water temperature is a major factor affecting poikilothermic organisms and their physiological processes since both, increases and decreases in water temperature, can induce the production of ROS (Lushchak, 2011).
Most poikilothermic species are adapted to different temperature ranges, as temperature is a major factor influencing their geographic distributions (TRUDGILL et al., 2005).
For poikilothermic marine animals such as the Iceland scallop, the growth rate of individuals in the fishable stock is regulated by seawater temperature, providing sufficient food is available (Jonasson et al.
Fish species are poikilothermic and their feed intake, growth and metabolic responses are affected by surrounding temperature (Peres and Oliva-Teles, 1999).
Ants are poikilothermic, thus their foraging activity depends on different abiotic factors like relative humidity and soil temperature (Traniello 1989; Valenzuela-Gonzalez et al.
Near-bottom temperatures prevalent on the Magdalen Shoals are extremely low throughout the year (Swain et al., 1998), and small variations in temperature may have dramatic effects on the developmental and transmission rates of helminth parasites, as well as on the distributions and developmental rates of their poikilothermic intermediate hosts.
As expected for poikilothermic animals, activity between cohorts differed, most likely reflecting seasonal patterns.
Cellular and humoral aspects of the influence of environmental temperature on the immune response of poikilothermic vertebrates.
Cellular aspects of hormonally controlled pigment translocations within chromatophores of poikilothermic vertebrates.