Mammalian Seasonal Rhythms: Behavior and Neuroendocrine Substrates

Prendergast, Brian J.; Nelson, Randy J.; Zucker, Irving H.

doi:10.1016/b978-008088783-8.00014-0

Cited by 94 publications

(117 citation statements)

References 271 publications

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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: 96%

Tracking the seasons: the internal calendars of vertebrates

Paul

Zucker

Schwartz

2007

Phil. Trans. R. Soc. B

175

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: 96%

Tracking the seasons: the internal calendars of vertebrates

Paul

Zucker

Schwartz

2007

Phil. Trans. R. Soc. B

175

152

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“…In adults, food-storing experience alone does not appear to alter the volume of the Hp in some species (Cristol, 1996); although combined with other seasonal effects, it may increase Hp volume, cell number, or new cell recruitment in other species such as the black-capped chickadee (Barnea & Nottebohm, 1994;Smulders et al, 1995;Smulders, Shiflett, Sperling, & DeVoogd, 2000). Changes in Hp neuroanatomy across seasons that are correlated with seasonal demand for spatial memory appear to be triggered directly by changes in photoperiod in some mammals (Prendergast, Nelson, & Zucker, 2002). In eastern gray squirrels, however, seasonal changes in photoperiod and food storing are not accompanied by changes in Hp volume (Lavenex, Steele, & Jacobs, 2000).…”

mentioning

confidence: 96%

Sex differences in the effects of captivity on hippocampus size in brown-headed cowbirds (Molothrus ater obscurus).

Day

Guerra²,

Schlinger³

et al. 2008

Behavioral Neuroscience

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In brood parasitic cowbirds, hippocampus (Hp) size is correlated with environmental spatial memory demands. Searching for host nests is the presumed causal factor influencing cowbird Hp size, because Hp volumes vary across species, sexes, and seasons according to nest-searching participation. Brownheaded cowbirds have female-only nest searching and, at least in the eastern subspecies, a larger Hp in females than in males, suggesting that nest searching influences cowbird Hp size. We predicted that female brown-headed cowbirds housed in aviaries lacking host nests would have a smaller Hp than wild-caught females whereas males would be unaffected. We found that the Hp was smaller in captive females, but not males, compared to their wild-caught counterparts. This did not appear to be due to general effects of an impoverished environment on all brain regions. Our results imply that interruption of nest searching in cowbirds prevents seasonal increase in Hp size in females. Future studies should isolate which behavioral differences between wild and captive birds contributed to captivity-induced changes in Hp volume in females while not affecting males. Keywordscowbird; hippocampus; sex differences; brain plasticity; brood parasitism Variation in environmental spatial demands is related to variation in hippocampus (Hp) size among closely related species, between sexes, and across seasons in mammalian, avian, and reptilian species. For example, food-storing behaviors in birds (Clayton, 1995a;Hampton, Sherry, Shettleworth, Kurgel, & Ivy, 1995;Hampton & Shettleworth, 1996;Healy & Krebs, 1992;Krebs, Sherry, Healy, Perry, & Vaccarion, 1989;Sherry, Vaccarino, Buckenham, & Herz, 1989;Volman, Grubb, & Schuett, 1997) and rodents (Jacobs, 1992;Jacobs & Spencer, 1994), foraging-related rate of movement in lacertid lizards (Day, Crews, & Wilczynski, 1999), home-range size in voles (Gaulin, 1992;Jacobs, Gaulin, Sherry, & Hoffman, 1990 Sherry, Jacobs, & Gaulin, 1992), and breeding-habitat complexity in petrels (Abbott, Walsh, Storey, Stenhause, & Harley, 1999) are all associated with enlarged Hp size, presumably due to the demands of spatial memory. In addition, seasonal variation in food-storing demands is associated with seasonal changes in Hp volume (Smulders, Sasson, & DeVoogd, 1995) in black-capped chickadees and rodents (Jacobs, 1996). Males have a larger Hp than females in a vole species in which males have larger home ranges but not in vole species that do not have sex differences in home range (Gaulin, 1992). These results provide evidence that environmental or experiential seasonal changes can alter Hp volume and that natural and sexual selection on a variety of spatial-related skills has produced a larger Hp in some species or sexes than in others.Although correlations of Hp volume with ecological demands for spatial ability are numerous, the specific mechanisms that contribute to such adult variation in the volume of the Hp are not well understood. We do know that species-specific reactions to spatial experience...

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“…Daily and seasonal rhythms are based on intrinsic timing mechanisms that integrate with predictive temporal cues such as day length, while buffering organisms from an acute change in the environment, such as a spell of high rise in temperature (Gwinner, 1986;Prendergast et al, 2002;Bradshaw and Holzapfel, 2007). These rhythms are not reactions to the light-dark (LD) cycle (Aschoff, 1981).…”

Section: Introductionmentioning

confidence: 99%

Persistence of circannual rhythms under constant periodic and aperiodic light conditions: sex differences and relationship with the external environment

Budki

Rani

Kumar

2012

Journal of Experimental Biology

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SUMMARYThe timing and duration of gonadal phases in the year indicates that breeding cycles are regulated by endogenous mechanisms. The present study on tropical spotted munia (Lonchura punctulata) investigates whether such mechanisms are based on circannual rhythms, and whether circannual rhythms between sexes differ in their relationship with the light environment. Birds were subjected to 12h light per day (12L:12D), alternate days of light and darkness (24L:24D, LL/DD) and continuous light (LL), with L22lx and D≤1lx, for 28months at constant temperature (18±1°C). Groups kept on natural day lengths (NDL) served as controls. Measurement of body mass, gonads and molts of the primary wing feathers and body plumage at regular intervals showed that birds underwent repeated cycles in gonads and molt, but not in body mass. Under NDL, gonadal phases in both sexes cycled with 12month periods. Under other conditions, males cycled with similar periods of ~11months, but females cycled with relatively large period variations, ~10-13months. Gonadal recrudescence-regression phase was longer in males than in females and, in both sexes, longer in the second year compared with the first year. The molt of wing primaries was more closely coupled to gonadal maturation in groups on NDL and 12L:12D than in groups on LL and LL/DD, but this relationship drifted apart in the second year. Body plumage molts were relatively more highly variable in both frequency and pattern in females than in males. It is suggested that annual breeding cycle in spotted munia is regulated by the self-sustained circannual rhythms, which probably interact with the annual photoperiodic cycle to synchronize breeding cycles to calendar year. Both sexes seem to have independent timing strategies, but females appear to share a greater role in defining the reproductive season in relation with the environment. Supplementary material available online at

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Mammalian Seasonal Rhythms: Behavior and Neuroendocrine Substrates

Cited by 94 publications

References 271 publications

Tracking the seasons: the internal calendars of vertebrates

Tracking the seasons: the internal calendars of vertebrates

Sex differences in the effects of captivity on hippocampus size in brown-headed cowbirds (Molothrus ater obscurus).

Persistence of circannual rhythms under constant periodic and aperiodic light conditions: sex differences and relationship with the external environment

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