Kleptothermy

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In biology, kleptothermy is any form of thermoregulation by which an animal shares in the metabolic thermogenesis of another animal. It may or may not be reciprocal, and occurs in both endotherms and ectotherms. [1] One of its forms is huddling. However, kleptothermy can happen between different species that share the same habitat, and can also happen in pre-hatching life where embryos are able to detect thermal changes in the environment.

Contents

This process requires two major conditions: the thermal heterogeneity created by the presence of a warm organism in a cool environment in addition to the use of that heterogeneity by another animal to maintain body temperatures at higher (and more stable) levels than would be possible elsewhere in the local area. [2] The purpose of this behaviour is to enable these groups to increase its thermal inertia, retard heat loss and/or reduce the per capita metabolic expenditure needed to maintain stable body temperatures. [2]

Kleptothermy is seen in cases where ectotherms regulate their own temperatures and exploit the high and constant body temperatures exhibited by endothermic species. [2] In this case, the endotherms involved are not only mammals and birds; they can be termites that maintain high and constant temperatures within their mounds where they provide thermal regimes that are exploited by a wide array of lizards, snakes and crocodilians.[ citation needed ] However, many cases of kleptothermy involve ectotherms sheltering inside the burrows used by endotherms to help maintain a high constant body temperature. [2]

Huddling

Male Canadian garter snakes huddle around a female after hibernation when mating. Snuggling garder snakes 001.JPG
Male Canadian garter snakes huddle around a female after hibernation when mating.

Huddling confers higher and more constant body temperatures than solitary resting. [3] Some species of ectotherms including lizards [4] and snakes, such as boa constrictors [5] and tiger snakes, [6] increase their effective mass by clustering tightly together. It is also widespread amongst gregarious endotherms such as bats [7] and birds (such as the mousebird [8] and emperor penguin [9] ) where it allows the sharing of body heat, particularly among juveniles.

Huddling in emperor penguins.

In white-backed mousebirds ( Colius colius), individuals maintain rest-phase body temperature above 32 °C despite air temperatures as low as -3.4 °C. [10] This rest-phase body temperature was synchronized among individuals that cluster. [10] Sometimes, kleptothermy is not reciprocal and might be accurately described as heat-stealing. For example, some male Canadian red sided garter snakes engage in female mimicry in which they produce fake pheromones after emerging from hibernation. [11] This causes rival males to cover them in a mistaken attempt to mate, and so transfer heat to them. [11] In turn, those males that mimic females become rapidly revitalized after hibernation (which depends upon raising their body temperature), giving them an advantage in their own attempts to mate. [11]

Bats cluster together to maintain high and constant body temperatures. Bat survey in Ohio - 02-10-2011 (5571821846).jpg
Bats cluster together to maintain high and constant body temperatures.

On the other hand, huddling allows emperor penguins ( Aptenodytes forsteri) to save energy, maintain a high body temperature and sustain their breeding fast during the Antarctic winter. [12] This huddling behaviour raises the ambient temperature that these penguins are exposed to above 0 °C (at average external temperatures of -17 °C). [12] As a consequence of tight huddles, ambient temperatures can be above 20 °C and can increase up to 37.5 °C, close to birds' body temperature. [12] Therefore, this complex social behaviour is what enables all breeders to get an equal and normal access to an environment which allows them to save energy and successfully incubate their eggs during the Antarctic winter. [12]

Habitat sharing

Many ectotherms exploit the heat produced by endotherms by sharing their nests and burrows. For example, mammal burrows are used by geckos and seabird burrows by Australian tiger snakes and New Zealand tuatara. [13] Termites create high and regulated temperatures in their mounds, and this is exploited by some species of lizards, snakes and crocodiles. [14] [15]

Research has shown such kleptothermy can be advantageous in cases such as the blue-lipped sea krait ( Laticauda laticaudata ), where these reptiles occupy a burrow of a pair of wedge-tailed shearwater incubating their chick. [2] This in turn, raises its body temperature to 37.5 °C (99.5 °F), compared to 31.7 °C (89.1 °F) when present in other habitats. [2] Its body temperature is also observed to be more stable. [2] On the other hand, burrows without birds did not provide this heat, being only 28 °C (82 °F). [2]

Another example would be the case of the fairy prion (Pachyptila turtur) that forms a close association with a medium-sized reptile, the tuatara ( Sphenodon punctatus ). [16] These reptiles share the burrows made by the birds, and often stay when the birds are present which helps maintain a higher body temperature. [16] Research has shown that fairy prions enable tuatara to maintain a higher body temperature through the night for several months of the year, October to January (austral spring to summer). [16] During the night, tuatara sharing a burrow with a bird had the most thermal benefits and helped maintain their body temperature up to 15 hours the next day. [16]

Pre-hatching life

Research done on embryos of Chinese softshell turtles ( Pelodiscus sinensis) falsify the assumption that behavioural thermoregulation is possible only for post-hatching stages of the reptile life history. [17] Remarkably, even undeveloped and tiny embryos were able to detect thermal differentials within the egg and move to exploit that small-scale heterogeneity. [17] Research has shown that this behaviour exhibited by reptile embryos may well enhance offspring fitness where movements of these embryos enabled them to maximize heat gain from their surroundings and thus increase their body temperatures. [17] This in turn leads to a variation in the embryonic development rate and the incubation period as well. [17] This could benefit the embryos in which a warmer incubation increases developmental rate and therefore accelerating the hatching process. [17]

On the other hand, decreased incubation periods also may minimize the embryo's exposure to risks of nest predation or lethal extremes thermal conditions where embryos move to cooler regions of the egg during periods of dangerously high temperatures. [17]

In addition, embryonic thermoregulation could enhance hatching fitness via modifications to a range of phenotypic traits where embryos with minimal temperature differences hatch at the same time decreasing the individuals' risk of predation. [17] Therefore, the developmental rates of embryos of reptiles are not passive consequences of maternally enforced decisions about the temperatures that the embryo will experience before hatching. [17] Instead, the embryo's behaviour and physiology combine, allowing the smallest embryos to control aspects of their own pre-hatching environment showing that the embryo is not simply a work in progress, but is a functioning organism with surprisingly sophisticated and effective behaviours. [17]

Evolution

Ectotherms and endotherms undergo different evolutionary perspectives where mammals and birds thermoregulate far more precisely than ectotherms. [18] A major benefit of precise thermoregulation is the ability to enhance performance through thermal specialization. [18] Therefore, mammals and birds are assumed to have evolved relatively narrow performance breadths. [18] Thus, the heterothermy of these endotherms would lead to losses of performance during certain periods and therefore genetic variation in thermosensitivity would enable the evolution of thermal generalists in more heterothermic species. [18] The physiologies of the endotherms allows them to adapt within the constraints imposed by genetics, development, and physics. [18]

On the other side, the mechanisms for thermoregulation did not evolve separately, but rather in connection with other functions. [19] These mechanisms were more likely quantitative rather than qualitative and it involved selection of appropriate habitats, changes in levels of locomotor activity, optimum energy liberation, and conservation of metabolic substrates. [19] The evolution of endothermy is directly linked to the selection for high levels of activity sustained by aerobic metabolism. [20] The evolution of the complex behaviour patterns among the birds and mammals requires the evolution of metabolic systems that support the activity prior to that. [20]

Endothermy in vertebrates evolved along separate, but parallel lines from different groups of reptilian ancestors. [20] The advantages of endothermy are manifested in the ability to occupy thermal areas that exclude many ectothermic vertebrates, a high degree of thermal independence from environmental temperature, high muscular power output and sustained levels of activity. [20] Endothermy, however, is energetically very expensive and requires a great deal of food, compared with ectotherms in order to support high metabolic rates. [20]

See also

Related Research Articles

<span class="mw-page-title-main">Warm-blooded</span> Animal species that can maintain a body temperature higher than their environment

Warm-blooded is an informal term referring to animal species whose bodies maintain a temperature higher than that of their environment. In particular, homeothermic species maintain a stable body temperature by regulating metabolic processes. Other species have various degrees of thermoregulation.

<span class="mw-page-title-main">Hibernation</span> Physiological state of dormant inactivity in order to pass the winter season

Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most commonly occurs during winter months.

<span class="mw-page-title-main">Homeothermy</span> Thermoregulation that maintains a stable internal body temperature regardless of external influence

Homeothermy, homothermy or homoiothermy is thermoregulation that maintains a stable internal body temperature regardless of external influence. This internal body temperature is often, though not necessarily, higher than the immediate environment. Homeothermy is one of the three types of thermoregulation in warm-blooded animal species. Homeothermy's opposite is poikilothermy. A poikilotherm is an organism that does not maintain a fixed internal temperature but rather fluctuates based on their environment and physical behaviour.

<span class="mw-page-title-main">Torpor</span> State of decreased physiological activity in an animal

Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the time a hibernator spends at low body temperature, lasting days to weeks, or it can refer to a period of low body temperature and metabolism lasting less than 24 hours, as in "daily torpor".

<span class="mw-page-title-main">Endotherm</span> Organism that maintains body temperature largely by heat from internal bodily functions

An endotherm is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions instead of relying almost purely on ambient heat. Such internally generated heat is mainly an incidental product of the animal's routine metabolism, but under conditions of excessive cold or low activity an endotherm might apply special mechanisms adapted specifically to heat production. Examples include special-function muscular exertion such as shivering, and uncoupled oxidative metabolism, such as within brown adipose tissue.

<span class="mw-page-title-main">Thermoregulation</span> Ability of an organism to keep its body temperature within certain boundaries

Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature as its own body temperature, thus avoiding the need for internal thermoregulation. The internal thermoregulation process is one aspect of homeostasis: a state of dynamic stability in an organism's internal conditions, maintained far from thermal equilibrium with its environment. If the body is unable to maintain a normal temperature and it increases significantly above normal, a condition known as hyperthermia occurs. Humans may also experience lethal hyperthermia when the wet bulb temperature is sustained above 35 °C (95 °F) for six hours. Work in 2022 established by experiment that a wet-bulb temperature exceeding 30.55°C caused uncompensable heat stress in young, healthy adult humans. The opposite condition, when body temperature decreases below normal levels, is known as hypothermia. It results when the homeostatic control mechanisms of heat within the body malfunction, causing the body to lose heat faster than producing it. Normal body temperature is around 37°C(98.6°F), and hypothermia sets in when the core body temperature gets lower than 35 °C (95 °F). Usually caused by prolonged exposure to cold temperatures, hypothermia is usually treated by methods that attempt to raise the body temperature back to a normal range. It was not until the introduction of thermometers that any exact data on the temperature of animals could be obtained. It was then found that local differences were present, since heat production and heat loss vary considerably in different parts of the body, although the circulation of the blood tends to bring about a mean temperature of the internal parts. Hence it is important to identify the parts of the body that most closely reflect the temperature of the internal organs. Also, for such results to be comparable, the measurements must be conducted under comparable conditions. The rectum has traditionally been considered to reflect most accurately the temperature of internal parts, or in some cases of sex or species, the vagina, uterus or bladder.

<span class="mw-page-title-main">Ectotherm</span> Organism where internal heating sources are small or negligible

An ectotherm, more commonly referred to as a "cold-bloodedanimal", is an animal in which internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature. Such organisms rely on environmental heat sources, which permit them to operate at very economical metabolic rates.

Thermogenesis is the process of heat production in organisms. It occurs in all warm-blooded animals, and also in a few species of thermogenic plants such as the Eastern skunk cabbage, the Voodoo lily, and the giant water lilies of the genus Victoria. The lodgepole pine dwarf mistletoe, Arceuthobium americanum, disperses its seeds explosively through thermogenesis.

<span class="mw-page-title-main">Egg incubation</span> The process by which certain egg-laying animals hatch their eggs

Egg incubation is the process by which an egg, of oviparous (egg-laying) animals, develops an embryo within the egg, after the egg's formation and ovipositional release. Egg incubation is done under favorable environmental conditions, possibly by brooding and hatching the egg.

<span class="mw-page-title-main">Gigantothermy</span> Form of thermoregulation by body size

Gigantothermy is a phenomenon with significance in biology and paleontology, whereby large, bulky ectothermic animals are more easily able to maintain a constant, relatively high body temperature than smaller animals by virtue of their smaller surface-area-to-volume ratio. A bigger animal has proportionately less of its body close to the outside environment than a smaller animal of otherwise similar shape, and so it gains heat from, or loses heat to, the environment much more slowly.

<span class="mw-page-title-main">Poikilotherm</span> Organism with considerable internal temperature variation

A poikilotherm is an animal whose internal temperature varies considerably. Poikilotherms have to survive and adapt to environmental stress. One of the most important stressors is temperature change, which can lead to alterations in membrane lipid order and can cause protein unfolding and denaturation at elevated temperatures. It is the opposite of a homeotherm, an animal which maintains thermal homeostasis. While the term in principle can apply to all organisms, it is generally only applied to animals, and mostly to vertebrates. Usually the fluctuations are consequence of variation in the ambient environmental temperature. Many terrestrial ectotherms are poikilothermic. However some ectotherms remain in temperature-constant environments to the point that they are actually able to maintain a constant internal temperature and are considered homeothermic. 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.

<span class="mw-page-title-main">Blue-lipped sea krait</span> Species of snake

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<span class="mw-page-title-main">Argentine black and white tegu</span> Species of lizard which is the largest of the tegu lizards

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<span class="mw-page-title-main">Eurytherm</span> Organism tolerant of a wide temperature range

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<span class="mw-page-title-main">Mesotherm</span> Type of animal that produces metabolic heat, but has no specific body temperature

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Albert Farrell Bennett is an American zoologist, physiologist, evolutionary biologist, author, and academic. He is Dean Emeritus of the School of Biological Sciences at University of California, Irvine.

References

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  13. ↑ Newman, DG (1987). "Burrow use and population densities of Tuatara (Sphenodon punctatus) and how they are influenced by fairy prions (Pachyptila turtur) on Stephens Island, New Zealand". Herpetologica. 43 (3): 336–344. JSTOR   3892500.
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