Is torpor a water conservation strategy? Heterothermic responses to acute water and food deprivation are repeatable among individuals of Phodopus sungorus.

Autor: Noakes MJ; Department of Vertebrate Zoology and Ecology, Nicolaus Copernicus University in Toruń, Poland; School of Animal, Plant, and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa. Electronic address: noakesmatthewj@gmail.com., Przybylska-Piech AS; Department of Vertebrate Zoology and Ecology, Nicolaus Copernicus University in Toruń, Poland., Wojciechowski MS; Department of Vertebrate Zoology and Ecology, Nicolaus Copernicus University in Toruń, Poland., Jefimow M; Department of Animal Physiology and Neurobiology, Nicolaus Copernicus University in Toruń, Poland.
Jazyk: angličtina
Zdroj: Journal of thermal biology [J Therm Biol] 2022 Oct; Vol. 109, pp. 103321. Date of Electronic Publication: 2022 Sep 05.
DOI: 10.1016/j.jtherbio.2022.103321
Abstrakt: Energy conservation is a clear function of torpor. Although many studies imply that torpor is also a water-saving strategy, the experimental evidence linking water availability with torpor is inconclusive. We tested the relative roles of water and energy shortages in driving torpor, using the Siberian hamster Phodopus sungorus as a model species. To account for the seasonal development of spontaneous heterothermy, we used male hamsters acclimated to short (8L:16D, SP; n = 40) and long (16L:8D, LP; n = 36) photoperiods. We continuously measured body temperature (T b ) during consecutive 32 h of complete removal of water, food, or both, separated by 7.5 d recovery periods. We predicted that all deprivation types would increase the frequency of spontaneous torpor in SP, and induce torpor in LP-acclimated hamsters. Individuals underwent each deprivation type twice in random orders. Food and water deprivation did not induce torpor in LP-acclimated P. sungorus. Patterns of torpor expression varied among deprivation types in SP individuals. Torpor frequency was significantly lower, but bouts were ∼2 h longer and 2.5 °C deeper, during water deprivation compared to food and food-and-water deprivation. Heterothermic responses to all deprivation types were repeatable among individuals. Different torpor patterns during water and food deprivation suggest that water and energy shortages are distinct physiological challenges. Deeper and longer bouts during water deprivation likely led to higher energy and water savings, while shorter and shallower bouts during fasting may reflect a trade-off between energy conservation and food-seeking activity. The lack of a difference between food- and food-and-water-deprived hamsters suggests a higher sensitivity to food than water shortage. This supports the traditional view that energy conservation is the major function of torpor, but suggests that water shortages may also modulate torpor use. The high repeatability of thermoregulatory responses to resource deprivation suggests that these may be heritable traits subject to natural selection.
Competing Interests: Declaration of competing interest None.
(Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)
Databáze: MEDLINE
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