Energy and time optimization during exit from torpor in vertebrate endotherms

Torpor is used in small sized birds and mammals as an energy conservation trait. Considerable effort has been put towards elucidating the mechanisms underlying its entry and maintenance, but little attention has been paid regarding the exit. Firstly, we demonstrate that the arousal phase has a stere...

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Bibliographic Details
Published in:Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Biochemical, systemic, and environmental physiology, 2023-08, Vol.193 (4), p.461-475
Main Authors: Nogueira-de-Sá, Pedro Goes, Bicudo, José Eduardo Pereira Wilken, Chaui-Berlinck, José Guilherme
Format: Article
Language:English
Subjects:
Animal Physiology
Animals
Arousal
Biochemistry
Biomedical and Life Sciences
Biomedicine
Birds - physiology
Body size
Body temperature
Body Temperature - physiology
Control systems
Energy conservation
Energy Metabolism
First principles
Hibernation
Hibernation - physiology
Human Physiology
Life Sciences
Mammals - physiology
Metabolic rate
Metabolism
Optimization
Original Paper
Torpor
Vertebrates
Zoology
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Summary:Torpor is used in small sized birds and mammals as an energy conservation trait. Considerable effort has been put towards elucidating the mechanisms underlying its entry and maintenance, but little attention has been paid regarding the exit. Firstly, we demonstrate that the arousal phase has a stereotyped dynamic: there is a sharp increase in metabolic rate followed by an increase in body temperature and, then, a damped oscillation in body temperature and metabolism. Moreover, the metabolic peak is around two-fold greater than the corresponding euthermic resting metabolic rate. We then hypothesized that either time or energy could be crucial variables to this event and constructed a model from a collection of first principles of physiology, control engineering and thermodynamics. From the model, we show that the stereotyped pattern of the arousal is a solution to save both time and energy. We extended the analysis to the scaling of the use of torpor by endotherms and show that variables related to the control system of body temperature emerge as relevant to the arousal dynamics. In this sense, the stereotyped dynamics of the arousal phase necessitates a certain profile of these variables which is not maintained as body size increases.
ISSN:0174-1578
1432-136X
DOI:10.1007/s00360-023-01494-5