Hibernation in the Extreme: Burrow and Body Temperatures, Metabolism, and Limits to Torpor Bout Length in Arctic Ground Squirrels

2000 ◽  
pp. 65-72 ◽  
Author(s):  
Brian M. Barnes ◽  
C. Loren Buck
Keyword(s):  
Ground Squirrels ◽  
Body Temperatures ◽  
Torpor Bout ◽  
Bout Length ◽  
Arctic Ground Squirrels

scholarly journals mRNA Stability and Polysome Loss in Hibernating Arctic Ground Squirrels (Spermophilus parryii)

2000 ◽  
Vol 20 (17) ◽  
pp. 6374-6379 ◽  
Author(s):  
Jason E. Knight ◽  
Erin Nicol Narus ◽  
Sandra L. Martin ◽  
Allan Jacobson ◽  
Brian M. Barnes ◽  
...  
Keyword(s):  
Mrna Stability ◽  
Functional Significance ◽  
Binding Protein ◽  
Ground Squirrels ◽  
Gene Products ◽  
Body Temperatures ◽  
Spermophilus Parryii ◽  
Torpor Bout ◽  
Arctic Ground Squirrels ◽  
The Stability

ABSTRACT All small mammalian hibernators periodically rewarm from torpor to high, euthermic body temperatures for brief intervals throughout the hibernating season. The functional significance of these arousal episodes is unknown, but one suggestion is that rewarming may be related to replacement of gene products lost during torpor due to degradation of mRNA. To assess the stability of mRNA as a function of the hibernation state, we examined the poly(A) tail lengths of liver mRNA from arctic ground squirrels sacrificed during four hibernation states (early and late during a torpor bout and early and late following arousal from torpor) and from active ground squirrels sacrificed in the summer. Poly(A) tail lengths were not altered during torpor, suggesting either that mRNA is stabilized or that transcription continues during torpor. In mRNA isolated from torpid ground squirrels, we observed a pattern of 12 poly(A) residues at greater densities approximately every 27 nucleotides along the poly(A) tail, which is a pattern consistent with binding of poly(A)-binding protein. The intensity of this pattern was significantly reduced following arousal from torpor and undetectable in mRNA obtained from summer ground squirrels. Analyses of polysome profiles revealed a significant reduction in polyribosomes in torpid animals, indicating that translation is depressed during torpor.

scholarly journals Facultative variation across a shallow to deep torpor spectrum in hummingbirds

2021 ◽  
Author(s):  
Anusha Shankar ◽  
Isabelle NH Cisneros ◽  
Sarah Thompson ◽  
Catherine H Graham ◽  
Donald R Powers
Keyword(s):  
Body Temperature ◽  
Energy Savings ◽  
Genetic Regulation ◽  
Bird Species ◽  
Ground Squirrels ◽  
Fine Scale ◽  
Body Temperatures ◽  
Natural Temperature ◽  
Balance Energy ◽  
Arctic Ground Squirrels

Many small endotherms use torpor, saving energy by a controlled reduction of their body temperature and metabolic rate. Some species (e.g. arctic ground squirrels, hummingbirds) enter deep torpor, dropping their body temperatures by 23-37 °C, while others can only enter shallow torpor (e.g., pigeons, 3-10 °C reductions). However, deep torpor in mammals can increase predation risk (unless animals are in burrows or caves), inhibit immune function, and result in sleep deprivation, so even for species that can enter deep torpor, facultative shallow torpor might help balance energy savings with these potential costs. Deep torpor occurs in three avian orders. Although the literature hints that some bird species can use both shallow and deep torpor, little empirical evidence of such an avian torpor spectrum exists. We infrared imaged three hummingbird species that are known to use deep torpor, under natural temperature and light cycles, to test if they were also capable of shallow torpor. All three species used both deep and shallow torpor, often on the same night. Depending on the species, they used shallow torpor for 5-35% of the night. The presence of a bird torpor spectrum indicates a capacity for fine-scale physiological and genetic regulation of avian torpid metabolism.

scholarly journals A heterothermic spectrum in hummingbirds

2022 ◽  
Author(s):  
Anusha Shankar ◽  
Isabelle N. H. Cisneros ◽  
Sarah Thompson ◽  
Catherine H. Graham ◽  
Donald R. Powers
Keyword(s):  
Energy Savings ◽  
Genetic Regulation ◽  
Bird Species ◽  
Ground Squirrels ◽  
Fine Scale ◽  
Body Temperatures ◽  
Trade Offs ◽  
Natural Temperature ◽  
Balance Energy ◽  
Arctic Ground Squirrels

Many endotherms use torpor, saving energy by a controlled reduction of their body temperature and metabolic rate. Some species (e.g., arctic ground squirrels, hummingbirds) enter deep torpor, dropping their body temperatures by 23-37°C, while others can only enter shallow torpor (e.g., pigeons, 3-10°C reductions). However, deep torpor in mammals can increase predation risk (unless animals are in burrows or caves), inhibit immune function, and result in sleep deprivation, so even for species that can enter deep torpor, facultative shallow torpor might help balance energy savings with these potential costs. Deep torpor occurs in three avian orders, but the trade-offs of deep torpor in birds are unknown. Although the literature hints that some bird species (mousebirds and perhaps hummingbirds) can use both shallow and deep torpor, little empirical evidence of such an avian heterothermy spectrum within species exists. We infrared imaged three hummingbird species that are known to use deep torpor, under natural temperature and light cycles, to test if they were also capable of shallow torpor. All three species used both deep and shallow torpor, often on the same night. Depending on the species, they used shallow torpor for 5-35% of the night. The presence of a heterothermic spectrum in these bird species indicates a capacity for fine-scale physiological and genetic regulation of avian torpid metabolism.

scholarly journals Habitat selection by arctic ground squirrels (Spermophilus parryii)

2010 ◽  
Vol 91 (5) ◽  
pp. 1251-1260 ◽  
Author(s):  
Oliver E. Barker ◽  
Andrew E. Derocher
Keyword(s):  
Habitat Selection ◽  
Ground Squirrels ◽  
Spermophilus Parryii ◽  
Arctic Ground Squirrels

MAPKs are differentially modulated in arctic ground squirrels during hibernation

2005 ◽  
Vol 80 (6) ◽  
pp. 862-868 ◽  
Author(s):  
Xiongwei Zhu ◽  
Mark A. Smith ◽  
George Perry ◽  
Yang Wang ◽  
Austin P. Ross ◽  
...  
Keyword(s):  
Ground Squirrels ◽  
Arctic Ground Squirrels

scholarly journals Interrelationships Among Timing of Hibernation, Reproduction, and Warming Soil in Free-Living Female Arctic Ground Squirrels

2012 ◽  
pp. 63-72 ◽  
Author(s):  
Cory T. Williams ◽  
Michael J. Sheriff ◽  
Franziska Kohl ◽  
Brian M. Barnes ◽  
C. Loren Buck
Keyword(s):  
Ground Squirrels ◽  
Free Living ◽  
Arctic Ground Squirrels

Parasympathetic influence on heart rate in euthermic and hibernating ground squirrels.

1995 ◽  
Vol 198 (4) ◽  
pp. 931-937 ◽  
Author(s):  
M B Harris ◽  
W K Milsom
Keyword(s):  
Heart Rate ◽  
Ambient Temperature ◽  
Parasympathetic Nervous System ◽  
Ground Squirrels ◽  
Relative Role ◽  
Body Temperatures ◽  
Inotropic Effects ◽  
Ambient Temperatures ◽  
Isolated Hearts ◽  
C 32

The relative role of the parasympathetic nervous system during deep hibernation is enigmatic. Conflicting hypotheses exist, and both sides draw support from investigations of vagal influence on the heart. Recent studies have shown cardiac chronotropic and inotropic effects of parasympathetic stimulation and inhibition in isolated hearts and anesthetized animals at hibernating body temperatures. No studies, however, have demonstrated such occurrences in undisturbed deeply hibernating animals. The present study documents respiratory-related alterations in heart rate during euthermia and hibernation at ambient temperatures of 15, 10 and 5 degrees C mediated by parasympathetic influence. During quiet wakefulness, euthermic squirrels breathed continuously and exhibited a 29% acceleration in heart rate during inspiration. During deep undisturbed hibernation, at 15, 10 and 5 degrees C ambient temperature, animals exhibited an episodic breathing pattern and body temperatures were slightly above ambient temperature. At each temperature, heart rate during the respiratory episode was greater than that during the apnea. The magnitude of this ventilatory tachycardia decreased with ambient temperature, being 108% at 15 degrees C, 32% at 10 degrees C and 11.5% at 5 degrees C. Animals exposed to 3% CO2 at 5 degrees C, which significantly increased ventilation, still exhibited an 11.7% increase in heart rate during breathing. Thus, the magnitude of the ventilation tachycardia was independent of the level of ventilation, at least over the range studied. Inhibition of vagus nerve conduction at 5 degrees C was achieved using localized nerve block. This led to an increase in apneic heart rate and abolished the ventilatory tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

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