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 Circannual Rhythm in Body Temperature, Torpor, and Sensitivity to A1 Adenosine Receptor Agonist in Arctic Ground Squirrels

2013 ◽  
Vol 28 (3) ◽  
pp. 201-207 ◽  
Author(s):  
Jasmine M. Olson ◽  
Tulasi R. Jinka ◽  
Lindy K. Larson ◽  
Jeffrey J. Danielson ◽  
Jeanette T. Moore ◽  
...  
Keyword(s):  
Body Temperature ◽  
Adenosine Receptor ◽  
Receptor Agonist ◽  
Ground Squirrels ◽  
Circannual Rhythm ◽  
A1 Adenosine Receptor ◽  
Adenosine Receptor Agonist ◽  
Arctic Ground Squirrels

Survival time of hypothermic white rats (15°C) and ground squirrels (10°C)

1960 ◽  
Vol 199 (3) ◽  
pp. 463-466 ◽  
Author(s):  
V. Popovic
Keyword(s):  
Body Temperature ◽  
Survival Time ◽  
Ground Squirrels ◽  
Sodium Pentobarbital ◽  
Body Temperatures ◽  
Survival Times ◽  
Young Rats ◽  
White Rats

The survival times of intensively cooled white rats decrease with their body temperatures. When cooled by Giaja's technique and maintained afterwards at a body temperature of 15°C rats survived 9 hours, but they could be revived by rewarming only during the first 5.5 hours of survival (biological survival). Similar biological survival times were found when the rats were cooled by other techniques, whether the cooling was much quicker or much slower. The survival time was also independent of the rate of rewarming from hypothermia. Survival was shortened by cooling after administration of sodium pentobarbital. Biological survival of young 40-gm rats at 15°C body temperature was 19 hours, 14 hours longer than that of hypothermic adults. Level of O2 consumption of hypothermic young rats differed from those of hypothermic adult animals.

scholarly journals BODY TEMPERATURE AND ACTIVITY PATTERNS IN FREE-LIVING ARCTIC GROUND SQUIRRELS

2005 ◽  
Vol 86 (2) ◽  
pp. 314-322 ◽  
Author(s):  
Ryan A. Long ◽  
Timothy J. Martin ◽  
Brian M. Barnes
Keyword(s):  
Body Temperature ◽  
Activity Patterns ◽  
Ground Squirrels ◽  
Free Living ◽  
Arctic Ground Squirrels

Hibernation and Circadian Rhythms of Body Temperature in Free-Living Arctic Ground Squirrels

2012 ◽  
Vol 85 (4) ◽  
pp. 397-404 ◽  
Author(s):  
Cory T. Williams ◽  
Brian M. Barnes ◽  
Melanie Richter ◽  
C. Loren Buck
Keyword(s):  
Body Temperature ◽  
Circadian Rhythms ◽  
Ground Squirrels ◽  
Free Living ◽  
Arctic Ground Squirrels

scholarly journals Daily body temperature rhythms persist under the midnight sun but are absent during hibernation in free-living arctic ground squirrels

2011 ◽  
Vol 8 (1) ◽  
pp. 31-34 ◽  
Author(s):  
Cory T. Williams ◽  
Brian M. Barnes ◽  
C. Loren Buck
Keyword(s):  
Body Temperature ◽  
Circadian Rhythms ◽  
Ground Squirrels ◽  
The Arctic ◽  
Constant Light ◽  
Polar Regions ◽  
Free Living ◽  
Active Season ◽  
Temperature Rhythms ◽  
Arctic Ground Squirrels

In indigenous arctic reindeer and ptarmigan, circadian rhythms are not expressed during the constant light of summer or constant dark of winter, and it has been hypothesized that a seasonal absence of circadian rhythms is common to all vertebrate residents of polar regions. Here, we show that, while free-living arctic ground squirrels do not express circadian rhythms during the heterothermic and pre-emergent euthermic intervals of hibernation, they display entrained daily rhythms of body temperature ( T b ) throughout their active season, which includes six weeks of constant sun. In winter, ground squirrels are arrhythmic and regulate core body temperatures to within ±0.2°C for up to 18 days during steady-state torpor. In spring, after the use of torpor ends, male but not female ground squirrels, resume euthermic levels of T b in their dark burrows but remain arrhythmic for up to 27 days. However, once activity on the surface begins, both sexes exhibit robust 24 h cycles of body temperature. We suggest that persistence of nycthemeral rhythms through the polar summer enables ground squirrels to minimize thermoregulatory costs. However, the environmental cues (zeitgebers) used to entrain rhythms during the constant light of the arctic summer in these semi-fossorial rodents are unknown.

Survival of newborn ground squirrels after supercooling or freezing

1963 ◽  
Vol 204 (5) ◽  
pp. 949-952 ◽  
Author(s):  
Pava Popovic ◽  
Vojin Popovic
Keyword(s):  
Body Temperature ◽  
Electrical Activity ◽  
Ground Squirrels ◽  
The Body ◽  
Esophageal Temperature ◽  
Body Temperatures ◽  
Dry Ice

Six of seven 2-day-old ground squirrels survived without any harmful consequences 11 hr supercooling to body temperatures of –3 to –4 C. Longer exposure at the same body temperature was not followed by survival. Of 12 ground squirrels which were kept at stabilized body temperatures of –6 and –8 C for 5 hr, 10 animals survived. Electrical activity of the heart was not detectable when the body temperature of ground squirrels was below –2 C. Immersion of newborn ground squirrels in –35 C alcohol-dry-ice mixture caused their bodies to freeze after 15–20 sec, suddenly turning white and rigid. Ground squirrels survived the freezing which lasted less than 2 min. At the end of 2 min immersion the esophageal temperature of cooled animals was –10 to –15 C.

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.

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