Circannual Rhythmicity in Hibernating Mammals

Pengelley, Eric T.

doi:10.1016/b978-0-12-550150-7.50011-4

Cited by 89 publications

(39 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…(b) Circannual clocks By contrast, golden-mantled ground squirrels housed under constant conditions (including static photoperiods) undergo several successive annual cycles of reproductive competence/incompetence with a period of approximately 10.5 months (Pengelley & Asmundson 1974). The largest variation in period for a given squirrel in this study was 29 days over four cycles, and in one squirrel there was only a 4-day variation in period.…”

Section: Annual Timekeeping Mechanismsmentioning

confidence: 86%

“…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: 97%

“…It does not require timed feedback from its physiological outputs (see Gwinner 1981b) and can track seasonal time even when its physiological expression is suppressed. Manipulations that either prevent the usual increase or accelerate the decrease in body mass have little or no effect on the onset or termination of the hibernation season, the period length between successive hibernation seasons or the onset of circannual weight gain in goldenmantled ground squirrels (Pengelley 1968;Heller & Poulson 1970;Pengelley & Asmundson 1974). Similar results have also been obtained in 13-lined ground squirrels (Spermophilus tridecemlineatus), whose energetic demands are increased by induced arousal from hibernation bouts without available food; with the return of food, the squirrels regain the proper body mass for that time of year (Mrosovsky & Fisher 1970).…”

Section: Annual Timekeeping Mechanismsmentioning

confidence: 99%

See 2 more Smart Citations

Tracking the seasons: the internal calendars of vertebrates

Paul

Zucker

Schwartz

2007

Phil. Trans. R. Soc. B

169

152

View full text Add to dashboard Cite

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.

show abstract

Section: Annual Timekeeping Mechanismsmentioning

confidence: 86%

Section: Annual Timekeeping Mechanismsmentioning

confidence: 97%

Section: Annual Timekeeping Mechanismsmentioning

confidence: 99%

See 1 more Smart Citation

Tracking the seasons: the internal calendars of vertebrates

Paul

Zucker

Schwartz

2007

Phil. Trans. R. Soc. B

169

152

View full text Add to dashboard Cite

show abstract

“…Cela suggère que le système endogène à l'origine de l'horloge circannuelle est issu de mécanismes ancestraux communs [4,5]. Nous avons ainsi montré que le hamster d'Europe (Cricetus cricetus), maintenu en conditions constantes de photopériode et de température, pré-sente un rythme circannuel de reproduction et de masse corporelle [3,6].…”

unclassified

Une horloge circannuelle sonne le réveil des hibernants

2015

View full text Add to dashboard Cite

“…Manifestation of the cycle in the presence of the alternating light and darkness indicated to them that light could not be an all-important cue or Zeitgeber. In fact, Pengelley and Asmundson (2) stated that "ambient temperature, light, access to motor activity, and opportunity to breed are all potential Zeitgebers." After reviewing results of the search by Pengelley and Fisher and by a number of other workers for a Zeitgeber, Mrosovsky (3) concluded that "If there is one, it certainly does not seem likely to involve light.…”

mentioning

confidence: 99%

Evidence for existence of a yearly clock in surgically and self-blinded chipmunks.

Richter¹

1978

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

By use of simplified technique and constant environmental conditions, I have demonstrated the existence in the chipmunk of a yearly clock. In a blinded chipmunk the clock manifested itself by remarkably consistent changes in running activity, food and water intake, and body weight over 61/2 yr. Studies on freshly trapped chipmunks kept in the same laboratory environment but with alternating light and darkness (12 hr each), showed that, when their eyes were covered for much of the light period, they reduced their exposure to light to preserve the activity of the yearly clock. Laboratory-adapted chipmunks that do not shield their eyes from light do not show the clock. The yearly clock has all the characteristics of the 24-hr clock, including sharply defined active and inactive phases, and must likewise play an important part in the animal's survival. Light would appear to be the chief or only cue for the clock. The period lengths did not change with age during the 61'2 yr.Men have long talked of yearly cycles but never has there been a clear demonstration under experimentally controlled conditions of a yearly clock that actually measures phases of activity followed by phases of total inactivity. This paper presents evidence supporting the existence of such a yearly clock-not simply of a yearly cycle or rhythm-and the importance of the role played by light in control of this clock.Pengelley and Fisher (1) found a yearly cycle in food intake and body weight in golden-mantled ground squirrels kept in alternating 12 hr of light and darkness and at external temperatures of 22°and 00. One animal at 220 showed two cycles and the other, at 00, showed 21/2 cycles. Manifestation of the cycle in the presence of the alternating light and darkness indicated to them that light could not be an all-important cue or Zeitgeber. In fact, Pengelley and Asmundson (2) stated that "ambient temperature, light, access to motor activity, and opportunity to breed are all potential Zeitgebers." After reviewing results of the search by Pengelley and Fisher and by a number of other workers for a Zeitgeber, Mrosovsky (3) concluded that "If there is one, it certainly does not seem likely to involve light."Most students of hibernation and heat conservation, particularly Pengelley and Fisher, Heller and Poulson (4), and Drescher (5), have made a point of always supplying their animals with "ample" nest-building material or closed boxes or nesting chambers. In this way the animals could cover or shield their entire bodies including their eyes, thus perhaps allowing them to functionally "blind" themselves. This could mean that in many instances in which animals seemed to be exposed to light they could have been "self-blinded." The present paper will bring out the importance of blinding that could have occurred in this way.Because studies on the 24-hr clock in mice, rats, hamsters, and squirrel monkeys established that blinding or constant darkness was necessary to free the 24-hr clock from its normal entrainment to light (6-), the present e...

show abstract

Circannual Rhythmicity in Hibernating Mammals

Cited by 89 publications

References 50 publications

Tracking the seasons: the internal calendars of vertebrates

Tracking the seasons: the internal calendars of vertebrates

Une horloge circannuelle sonne le réveil des hibernants

Evidence for existence of a yearly clock in surgically and self-blinded chipmunks.

Contact Info

Product

Resources

About