Seasonal reproductive endothermy in tegu lizards

Tattersall, Glenn J.; Leite, Cléo A. C.; Sanders, Colin E.; Cadena, Viviana; Andrade, Denis V.; Abe, Augusto Shinya; Milsom, William K.

doi:10.1126/sciadv.1500951

Cited by 99 publications

(80 citation statements)

References 49 publications

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“…With a few notable exceptions (eg. [14]), ectotherms predominantly rely on external sources of heat production and therefore have a relatively consistent, and thus predictable, relationship between ambient temperature (T a ) and body temperature (T b ) [9,15,16]. By contrast, endotherms can generate heat using metabolism and as such T b is generally independent of T a [17].…”

Section: Introductionmentioning

confidence: 99%

Modelling mammalian energetics: the heterothermy problem

Levesque

Nowack

Stawski

2016

Clim Chang Responses

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Global climate change is expected to have strong effects on the world's flora and fauna. As a result, there has been a recent increase in the number of meta-analyses and mechanistic models that attempt to predict potential responses of mammals to changing climates. Many models that seek to explain the effects of environmental temperatures on mammalian energetics and survival assume a constant body temperature. However, despite generally being regarded as strict homeotherms, mammals demonstrate a large degree of daily variability in body temperature, as well as the ability to reduce metabolic costs either by entering torpor, or by increasing body temperatures at high ambient temperatures. Often, changes in body temperature variability are unpredictable, and happen in response to immediate changes in resource abundance or temperature. In this review we provide an overview of variability and unpredictability found in body temperatures of extant mammals, identify potential blind spots in the current literature, and discuss options for incorporating variability into predictive mechanistic models.

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Section: Introductionmentioning

confidence: 99%

Modelling mammalian energetics: the heterothermy problem

Levesque

Nowack

Stawski

2016

Clim Chang Responses

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“…Tighter regulation of T b during near-term gestation has also been demonstrated in echidnas (Tachyglossus aculeatus), bats (Eptesicus fuscus) and dunnarts (Sminthopsis macroura) [19], and more recently support for the PCM has been found in the remarkable discovery of reproductive endothermy in a small (approx. 2 kg) reptile (tegu lizard; Salvator merianae) [20,21]. Although data on freeranging large mammals during reproduction are scarce, if the PCM does explain increased homeothermy during gestation in lions, we might expect to observe it also in other species.…”

Section: Discussionmentioning

confidence: 99%

Improved homeothermy and hypothermia in African lions during gestation

et al. 2016

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Mammals use endogenously produced heat to maintain a high and relatively constant core body temperature (T b ). How they regulate their T b during reproduction might inform us as to what thermal conditions are necessary for optimal development of offspring. However, few studies have measured T b in free-ranging animals for sufficient periods of time to encounter reproductive events. We measured T b continuously in six free-ranging adult female African lions (Panthera leo) for approximately 1 year. Lions reduced the 24 h amplitude of T b by about 25% during gestation and decreased mean 24 h T b by 1.3 + 0.18C over the course of the gestation, reducing incidences of hyperthermia (T b . 39.58C). The observation of improved homeothermy during reproduction may support the parental care model (PCM) for the evolution of endothermy, which postulates that endothermy arose in birds and mammals as a consequence of more general selection for parental care. According to the PCM, endothermy arose because it enabled parents to better control incubation temperature, leading to rapid growth and development of offspring and thus to fitness benefits for the parents. Whether the precision of T b regulation in pregnant lions, and consequently their reproductive success, will be influenced by changing environmental conditions, particularly hotter and drier periods associated with climate change, remains to be determined.

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“…Another explanation might be that the reduced T b during basking maximises the dorsal heat uptake because of the increased temperature differential, and also minimises ventral heat loss. Differential vasoconstrictions could further aid in this (Tattersall et al, 2016). The T b and MR reduction makes sense from an energetic and ecological point of view because in the presence of radiant heat the animals can return T b to normothermic values at little energetic cost.…”

Section: Discussionmentioning

confidence: 99%

Basking hamsters reduce resting metabolism, body temperature and energy costs during rewarming from torpor

Geiser

Gasch

Bieber

et al. 2016

Journal of Experimental Biology

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Basking can substantially reduce thermoregulatory energy expenditure of mammals. We tested the hypothesis that the largely white winter fur of hamsters (Phodopus sungorus), originating from Asian steppes, may be related to camouflage to permit sun basking on or near snow. Winter-acclimated hamsters in our study were largely white and had a high proclivity to bask when resting and torpid. Resting hamsters reduced metabolic rate (MR) significantly (>30%) when basking at ambient temperatures (T a ) of ∼15 and 0°C. Interestingly, body temperature (T b ) also was significantly reduced from 34.7±0.6°C (T a 15°C, not basking) to 30.4±2.0°C (T a 0°C, basking), which resulted in an extremely low (<50% of predicted) apparent thermal conductance. Induced torpor (food withheld) during respirometry at T a 15°C occurred on 83.3±36.0% of days and the minimum torpor MR was 36% of basal MR at an average T b of 22.0±2.6°C; movement to the basking lamp occurred at T b <20.0°C. Energy expenditure for rewarming was significantly reduced (by >50%) during radiant heat-assisted rewarming; however, radiant heat per se without an endogenous contribution by animals did not strongly affect metabolism and T b during torpor. Our data show that basking substantially modifies thermal energetics in hamsters, with a drop of resting T b and MR not previously observed and a reduction of rewarming costs. The energy savings afforded by basking in hamsters suggest that this behaviour is of energetic significance not only for mammals living in deserts, where basking is common, but also for P. sungorus and probably other cold-climate mammals.

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Seasonal reproductive endothermy in tegu lizards

Abstract: Ectothermic lizards become endothermic in the breeding season, supporting a parental care model for the origins of endothermy.

Cited by 99 publications

References 49 publications

Modelling mammalian energetics: the heterothermy problem

Modelling mammalian energetics: the heterothermy problem

Improved homeothermy and hypothermia in African lions during gestation

Basking hamsters reduce resting metabolism, body temperature and energy costs during rewarming from torpor

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