Onset and Cessation of Hibernation under Constant Temperature and Light in the Golden-mantled Ground Squirrel (Citellus lateralis)

Pengelley, Eric T.; Fisher, Kenneth C.

doi:10.1038/1801371b0

Cited by 70 publications

(26 citation statements)

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“…Here, we illustrate this concept with reference to annual cycles of gonadal size and function, which are in breeding condition for both squirrels and hamsters during the spring and for hamsters in the summer as well (McKeever 1964;Figala et al 1973). A similar argument can be made, however, using other seasonal traits of these species (figure 2; Pengelley & Fisher 1957;Pengelley & Asmundson 1974;Prendergast et al 2002b).…”

Section: Annual Timekeeping Mechanismsmentioning

confidence: 83%

Tracking the seasons: the internal calendars of vertebrates

Paul

Zucker

Schwartz

2007

Phil. Trans. R. Soc. B

173

152

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Animals have evolved many season-specific behavioural and physiological adaptations that allow them to both cope with and exploit the cyclic annual environment. Two classes of endogenous annual timekeeping mechanisms enable animals to track, anticipate and prepare for the seasons: a timer that measures an interval of several months and a clock that oscillates with a period of approximately a year. Here, we discuss the basic properties and biological substrates of these timekeeping mechanisms, as well as their reliance on, and encoding of environmental cues to accurately time seasonal events. While the separate classification of interval timers and circannual clocks has elucidated important differences in their underlying properties, comparative physiological investigations, especially those regarding seasonal prolactin secretions, hint at the possibility of common substrates.Keywords: seasonality; photoperiodism; circannual; interval timers While the Earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease.Genesis 8: 22, King James Version (1611) As the Earth makes its yearly orbit around the Sun, the planet's 23.58 axial tilt leads to the cyclical environmental changes that we call the seasons. Recurrent challenges to the survival of organisms and their offspring arise with the dawning of each new season, and animals have evolved seasonally induced changes in phenotype that adapt them to these predictable events. For example, in many temperate environments, winter is generally characterized by severe decreases in ambient temperature and food availability, leading to increased energetic demands at a time when resources are diminished. Because energy requirements of female mammals typically increase markedly during lactation (Bronson 1989) and newly weaned offspring are particularly vulnerable to environmental perturbations (Hill 1992), raising offspring during this time of year is often futile. Thus, many temperate species have evolved winter-specific behaviours and physiology to conserve energy (e.g. hibernation, a more insulative pelage, huddling) or provide for escape (e.g. migration). Many species also increase the chances of offspring survival by timing their mating behaviours so that parturition occurs during energetically favourable times of year.

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Section: Annual Timekeeping Mechanismsmentioning

confidence: 83%

Tracking the seasons: the internal calendars of vertebrates

Paul

Zucker

Schwartz

2007

Phil. Trans. R. Soc. B

173

152

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“…7,8 Nonetheless, there are also melatonin-independent components to the seasonal response. 10 For a number of long-lived species, circannual cycles are now welldocumented, 11,12 although even species with short life-spans retain elements of circannual rhythms in their seasonal cycle. For short-day breeders, such as sheep, this means that extended exposure to long photoperiod triggers a spontaneous switch from anoestrus to oestrus.…”

Section: Mel Atonin Is the Photoperi Od I C Me Ssag Ementioning

confidence: 99%

“…Such circannual rhythms were first described in golden-mantled ground squirrels held under a fixed photoperiod and temperature, yet they showed annual cycles in food intake, body weight and hibernation. 10 For a number of long-lived species, circannual cycles are now welldocumented, 11,12 although even species with short life-spans retain elements of circannual rhythms in their seasonal cycle. 13…”

Section: Mel Atonin Is the Photoperi Od I C Me Ssag Ementioning

confidence: 99%

A unifying hypothesis for control of body weight and reproduction in seasonally breeding mammals

Helfer

Barrett

Morgan

2019

J Neuroendocrinology

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Animals have evolved diverse seasonal variations in physiology and reproduction to accommodate yearly changes in environmental and climatic conditions. These changes in physiology are initiated by changes in photoperiod (daylength) and are mediated through melatonin, which relays photoperiodic information to the pars tuberalis of the pituitary gland. Melatonin drives thyroid‐stimulating hormone transcription and synthesis in the pars tuberalis, which, in turn, regulates thyroid hormone and retinoic acid synthesis in the tanycytes lining the third ventricle of the hypothalamus. Seasonal variation in central thyroid hormone signalling is conserved among photoperiodic animals. Despite this, different species adopt divergent phenotypes to cope with the same seasonal changes. A common response amongst different species is increased hypothalamic cell proliferation/neurogenesis in short photoperiod. That cell proliferation/neurogenesis may be important for seasonal timing is based on (i) the neurogenic potential of tanycytes; (ii) the fact that they are the locus of striking seasonal morphological changes; and (iii) the similarities to mechanisms involved in de novo neurogenesis of energy balance neurones. We propose that a decrease in hypothalamic thyroid hormone and retinoic acid signalling initiates localised neurodegeneration and apoptosis, which leads to a reduction in appetite and body weight. Neurodegeneration induces compensatory cell proliferation from the neurogenic niche in tanycytes and new cells are born under short photoperiod. Because these cells have the potential to differentiate into a number of different neuronal phenotypes, this could provide a mechanistic basis to explain the seasonal regulation of energy balance, as well as reproduction. This cycle can be achieved without changes in thyroid hormone/retinoic acid and explains recent data obtained from seasonal animals held in natural conditions. However, thyroid/retinoic acid signalling is required to synchronise the cycles of apoptosis, proliferation and differentiation. Thus, hypothalamic neurogenesis provides a framework to explain diverse photoperiodic responses.

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“…However, a relatively few investigators (Hock (1955), Pengelley and Fisher (1957), Panuska (1959), Kalabukov (1960), Bartholomew and Hudson (1960)) have attempted to. elucidate some of the external environmental factors which may influence t h e beginning and termination of hibernation.…”

Section: Introductionmentioning

confidence: 98%

The Effect of Temperature and Photoperiod on the Yearly Hibernating Behavior of Captive Golden-Mantled Ground Squirrels (Citellus Lateralis Tescorum)

Pengelley¹,

Fisher²

1963

Can. J. Zool.

Self Cite

179

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The state of torpidity (hibernation), the food consumption, and the weight of a number of C. lateralis were recorded daily, weekly, and weekly, respectively, for periods up to 2 years. At ambient temperatures of 32" F , 70' F , and 95-100' F and under constant lighting conditions, all animals displayed an approximately 1-year cyclic variation in weight which roughly paralleled the consumption of food. Under these constant conditions of light and temperature the animals subjected to 32O F and 70" F hibernated, i.e., their body temperature dropped nearly to the ambient and they became torpid. The body temperature of animals kept a t 95-100' F could not drop and these animals did not become torpid.Hibernation could not be induced by removal of food but was greatly prolonged if food was not present in the cages a t the time the whole hibernation period was ending. The onset of hibernation could be changed only slightly by changing the day lengths. Hibernation was possible only a t a specific stage of the weight cycle. The length of the weight cycle was shortened by exposure to an ambient temperature of 95-100" F. By manipulation of the length of the exposure to the high temperature it was possible to have animals hibernating in summer and active in winter. I t was not possible to produce a similar shift in the phase of the weight cycle, and hence of hibernation, by changing the lighting conditions.

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Onset and Cessation of Hibernation under Constant Temperature and Light in the Golden-mantled Ground Squirrel (Citellus lateralis)

Cited by 70 publications

References 0 publications

Tracking the seasons: the internal calendars of vertebrates

Tracking the seasons: the internal calendars of vertebrates

A unifying hypothesis for control of body weight and reproduction in seasonally breeding mammals

The Effect of Temperature and Photoperiod on the Yearly Hibernating Behavior of Captive Golden-Mantled Ground Squirrels (Citellus Lateralis Tescorum)

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