Relationship of light intensity and photoperiod to circannual rhythmicity in the hibernating ground squirrel, Citellus lateralis

Pengelley, Eric T.; Asmundson, Sally J.; Barnes, Brian M.; Aloia, Roland C.

doi:10.1016/s0300-9629(76)80035-7

Cited by 57 publications

(26 citation statements)

References 20 publications

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“…Experimental animals were assigned to two temperature treatments (+2 or -10°C) and three hibernation durations at each temperature (45, 68 or 90days) for a total of six treatment groups (N5 per group, N30 total). Because squirrels in captivity under constant conditions may shorten their annual cycle, leading to decreased hibernation duration (Pengelley et al, 1976), we selected relatively short durations and assigned additional squirrels to each temperature treatment. One of these extra animals was allowed to hibernate for 115days at -10°C and four squirrels at +2°C were sampled after naturally terminating hibernation after 82, 139, 177 and 232days.…”

Section: Methodsmentioning

confidence: 99%

A test of alternate models for increased tissue nitrogen isotope ratios during fasting in hibernating arctic ground squirrels

Lee

Buck

Barnes

et al. 2012

Journal of Experimental Biology

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Section: Methodsmentioning

confidence: 99%

A test of alternate models for increased tissue nitrogen isotope ratios during fasting in hibernating arctic ground squirrels

Lee

Buck

Barnes

et al. 2012

Journal of Experimental Biology

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“…Obligate hibernators follow an endogenous circannual rhythm and hibernate each year, regardless of environmental conditions. This fact is dramatically illustrated by the research of Pengelley and colleagues, who showed that golden-mantled ground squirrels (Callospermophilus lateralis), born in captivity and maintained under constant light and temperature, hibernated each year, close to when winter would begin in the wild, at least in the first year following birth (225,226). It is common to see late-summer or autumn torpor in captive ground squirrels housed at warm ambient temperatures and long photoperiods after they have reached their peak body mass or adiposity (247).…”

Section: Obligate Versus Facultative Hibernatorsmentioning

confidence: 99%

“…The free-running cycle of this endogenous rhythm has a period of approximately 300 days in golden-mantled ground squirrels (225,226). The cycle is entrained and affected by environmental conditions (see ref.…”

Section: Obligate Versus Facultative Hibernatorsmentioning

confidence: 99%

Metabolic Flexibility: Hibernation, Torpor, and Estivation

Staples

2016

Comprehensive Physiology

127

116

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Many environmental conditions can constrain the ability of animals to obtain sufficient food energy, or transform that food energy into useful chemical forms. To survive extended periods under such conditions animals must suppress metabolic rate to conserve energy, water, or oxygen. Amongst small endotherms, this metabolic suppression is accompanied by and, in some cases, facilitated by a decrease in core body temperature-hibernation or daily torpor-though significant metabolic suppression can be achieved even with only modest cooling. Within some ectotherms, winter metabolic suppression exceeds the passive effects of cooling. During dry seasons, estivating ectotherms can reduce metabolism without changes in body temperature, conserving energy reserves, and reducing gas exchange and its inevitable loss of water vapor. This overview explores the similarities and differences of metabolic suppression among these states within adult animals (excluding developmental diapause), and integrates levels of organization from the whole animal to the genome, where possible. Several similarities among these states are highlighted, including patterns and regulation of metabolic balance, fuel use, and mitochondrial metabolism. Differences among models are also apparent, particularly in whether the metabolic suppression is intrinsic to the tissue or depends on the whole-animal response. While in these hypometabolic states, tissues from many animals are tolerant of hypoxia/anoxia, ischemia/reperfusion, and disuse. These natural models may, therefore, serve as valuable and instructive models for biomedical research.

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“…Obligate hibernators apparently follow an endogenous circannual rhythm, and 'must' hibernate each year, regardless of environmental conditions. This fact is dramatically illustrated by Pengelley and colleagues' research, which showed that goldenmantled ground squirrels (Callospermophilus lateralis), born in captivity and maintained under constant light and temperature, hibernated each year, close to when winter would begin in the wild (Pengelley et al, 1976). Facultative hibernators, such as the Syrian hamster (Mesocricetus auratus), can hibernate at any time of the year, but require acclimation for several weeks to cold temperatures.…”

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confidence: 99%

Metabolic suppression in mammalian hibernation: the role of mitochondria

Staples

2014

Journal of Experimental Biology

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Hibernation evolved in some small mammals that live in cold environments, presumably to conserve energy when food supplies are low. Throughout the winter, hibernators cycle spontaneously between torpor, with low metabolism and near-freezing body temperatures, and euthermia, with high metabolism and body temperatures near 37°C. Understanding the mechanisms underlying this natural model of extreme metabolic plasticity is important for fundamental and applied science. During entrance into torpor, reductions in metabolic rate begin before body temperatures fall, even when thermogenesis is not active, suggesting active mechanisms of metabolic suppression, rather than passive thermal effects. Mitochondrial respiration is suppressed during torpor, especially when measured in liver mitochondria fuelled with succinate at 37°C in vitro. This suppression of mitochondrial metabolism appears to be invoked quickly during entrance into torpor when body temperature is high, but is reversed slowly during arousal when body temperature is low. This pattern may reflect body temperaturesensitive, enzyme-mediated post-translational modifications of oxidative phosphorylation complexes, for instance by phosphorylation or acetylation.KEY WORDS: Heat, Body temperature, Thermoregulation, Thermogenesis, Oxidative phosphorylation, Post-translational modification, Acetylation, Phosphorylation IntroductionMost mammals are strict endotherms, i.e. they maintain fairly constant body temperatures (T b ) near 37°C using heat derived primarily from endogenous metabolism. In cold environments, mammals retain some of this heat by regulating insulation (using underfur and/or subcutaneous fat), peripheral blood circulation (using vasoconstriction and/or countercurrent heat exchangers) and ventilatory evaporation. At very cold temperatures, the high gradient between T b and ambient temperature (T a ) causes large heat loss by radiation and conduction, which is also affected by convection of water or air. For small mammals, the high body surface area, relative to volume, results in greater mass-specific rates of heat loss. While large land mammals can increase insulation by changing the quality (microstructure) and quantity (length, density) of underfur, this option is limited for small mammals. Imagine a 70 mm long lemming growing fur 100 mm long; it might stay warm, but when it tripped over that fur it would be easy prey.Despite the challenges, many small mammals thrive in cold environments. To compensate for high heat loss, these mammals upregulate their capacities to produce metabolic heat. Though COMMENTARY Department of Biology, University of Western Ontario, London, ON, Canada, N6A 5B8.*Author for correspondence (jfstaple@uwo.ca) effective, this strategy requires large quantities of fuel during winter when food availability is typically low. Many small mammals use stored food to power thermogenic metabolism. For example, American red squirrels (Tamiascurius hudsonicus) cache spruce cones and feed on the seeds throughout winter, allowing th...

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Relationship of light intensity and photoperiod to circannual rhythmicity in the hibernating ground squirrel, Citellus lateralis

Cited by 57 publications

References 20 publications

A test of alternate models for increased tissue nitrogen isotope ratios during fasting in hibernating arctic ground squirrels

A test of alternate models for increased tissue nitrogen isotope ratios during fasting in hibernating arctic ground squirrels

Metabolic Flexibility: Hibernation, Torpor, and Estivation

Metabolic suppression in mammalian hibernation: the role of mitochondria

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