Body Temperature and Activity Rhythms Under Different Photoperiods in High Arctic Svalbard ptarmigan (Lagopus muta hyperborea)

Appenroth, Daniel; Nord, Andreas; Hazlerigg, David G.; Wagner, Gabriela

doi:10.3389/fphys.2021.633866

Cited by 8 publications

(14 citation statements)

References 43 publications

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“…Diurnal modulation of UR power and/or period is evident in both sexes of numerous species, including other mouse strains (BALB/c (Smarr et al, 2016; Smarr et al, 2017)), hamsters (Prendergast and Zucker, 2012), rats (Wollnik and Dohler, 1986), common and tundra voles (van Rosmalen and Hut, 2021), and several arctic vertebrates (van Oort et al, 2007; Bloch et al, 2013; Appenroth et al, 2021). The present data extend these observations to C57 mice and quantify the influence of circadian phase on URs in finer detail.…”

Section: Discussionmentioning

confidence: 99%

“…URs exhibit remarkable plasticity as the circadian system entrains to seasonal changes in photoperiod: under short (winter) photoperiods nocturnal locomotor activity URs of mice (Refinetti, 2002), hamsters (Prendergast and Zucker, 2012), and rats (Siebert and Wollnik, 1991) become more prominent. In the field, when extremely long and short photoperiods prevail, arctic species (e.g., reindeer, ptarmigan) largely abandon CRs in favor of robust URs (van Oort et al, 2007;Bloch et al, 2013;Appenroth et al, 2021), challenging the hegemony of circadian rhythmicity (Hazlerigg and Tyler, 2019). allowed quantification of ultradian rhythms with appropriate time-frequency resolution, generating accurate, and repeatable measures of period and power which are suitable for group-level analyses.…”

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confidence: 99%

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Modified Wavelet Analyses Permit Quantification of Dynamic Interactions Between Ultradian and Circadian Rhythms

et al. 2022

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Circadian rhythms provide daily temporal structure to cellular and organismal biological processes, ranging from gene expression to cognition. Higher-frequency (intradaily) ultradian rhythms are similarly ubiquitous but have garnered far less empirical study, in part because of the properties that define them—multimodal periods, non-stationarity, circadian harmonics, and diurnal modulation–pose challenges to their accurate and precise quantification. Wavelet analyses are ideally suited to address these challenges, but wavelet-based measurement of ultradian rhythms has remained largely idiographic. Here, we describe novel analytical approaches, based on discrete and continuous wavelet transforms, which permit quantification of rhythmic power distribution across a broad ultradian spectrum, as well as precise identification of period within empirically determined ultradian bands. Moreover, the aggregation of normalized wavelet matrices allows group-level analyses of experimental treatments, thereby circumventing limitations of idiographic approaches. The accuracy and precision of these wavelet analyses were validated using in silico and in vivo models with known ultradian features. Experiments in male and female mice yielded robust and repeatable measures of ultradian period and power in home cage locomotor activity, confirming and extending reports of ultradian rhythm modulation by sex, gonadal hormones, and circadian entrainment. Seasonal changes in day length modulated ultradian period and power, and exerted opposite effects in the light and dark phases of the 24 h day, underscoring the importance of evaluating ultradian rhythms with attention to circadian phase. Sex differences in ultradian rhythms were more prominent at night and depended on gonadal hormones in male mice. Thus, relatively straightforward modifications to the wavelet procedure allowed quantification of ultradian rhythms with appropriate time-frequency resolution, generating accurate, and repeatable measures of period and power which are suitable for group-level analyses. These analytical tools may afford deeper understanding of how ultradian rhythms are generated and respond to interoceptive and exteroceptive cues.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Modified Wavelet Analyses Permit Quantification of Dynamic Interactions Between Ultradian and Circadian Rhythms

et al. 2022

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“…This indicates that these two rhythms are not perfectly synchronized even though they often are highly correlated under laboratory conditions in e.g., rodents ( Refinetti, 1997 , 1999 ; Weinert & Waterhouse, 1998 ). A study on Svalbard ptarmigan found a rise in T b preceding the light-on signal as well as the rise in activity connected to the light-on signal, suggesting an anticipatory function through the diel system ( Appenroth et al, 2021 ). The same may apply for rhythms in T b in Scandinavian brown bears.…”

Section: Discussionmentioning

confidence: 99%

Seasonality in Biological Rhythms in Scandinavian brown Bears

et al. 2022

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Biological rhythms, such as rhythms in activity and body temperature, are usually highly synchronized and entrained by environmental conditions, such as photoperiod. However, how the expression of these rhythms changes during hibernation, when the perception of environmental cues is limited, has not yet been fully understood for all hibernators, especially in the wild. The brown bear (Ursus arctos) in Scandinavia lives in a highly seasonal environment and adapts to harsh winter conditions by exhibiting hibernation, characterized by reduced metabolism and activity. In this study, we aimed to explore the expression of biological rhythms in activity, body temperature and heart rate of free-ranging brown bears over the annual cycle, including active, hibernation and the transition states around den entry and exit. We found that rhythms in physiology and activity are mostly synchronized and entrained by the light-dark cycle during the bears’ active state with predominantly diel and ultradian rhythms for body temperature, activity and heart rate. However, during hibernation, rhythms in body temperature and heart rate were considerably slowed down to infradian rhythms, influenced by the amount of snow in the denning area, whereas rhythms in activity remained diel. Rhythms in the transition states when bears prepared for entering or coming out of hibernation state displayed a combination of infradian and diel rhythms, indicating the preparation of the body for the change in environmental conditions. These results reveal that brown bears adjust their biological rhythms to the seasonal environment they inhabit. Rhythms in physiology and activity show simultaneity during the active state but are partly disconnected from each other during hibernation, when bears are most sheltered from the environment.

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“…Animals living in a constant environment like this can experience shifts in their circadian rhythm. For instance, patterns of activity become arrhythmic in arctic mammals when they are confronted with continuous dark or light conditions (van Oort et al 2005 ; Appenroth et al 2021 ) and circadian patterns in the timing of arousal from torpor are lost in some hibernators (e.g., Körtner and Geiser 2000 ; Revel et al 2007 ; Williams et al 2017 ). The loss of circadian rhythmicity in torpor timing therefore supports the notion that these bats cease foraging during this time of year (Razakarivony et al 2005 ; Goodman 2006 ; Rakotoarivelo et al 2007 ; Reher et al 2019 ), even though it is likely that not all were hibernating.…”

Section: Discussionmentioning

confidence: 99%

Disparate roost sites drive intraspecific physiological variation in a Malagasy bat

et al. 2021

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Many species are widely distributed and individual populations can experience vastly different environmental conditions over seasonal and geographic scales. With such a broad ecological reality, datasets with limited spatial and temporal resolution may not accurately represent a species and could lead to poorly informed management decisions. Because physiological flexibility can help species tolerate environmental variation, we studied the physiological responses of two separate populations of Macronycteris commersoni, a bat widespread across Madagascar, in contrasting seasons. The populations roost under the following dissimilar conditions: either a hot, well-buffered cave or within open foliage, unprotected from the local weather. We found that flexible torpor patterns, used in response to prevailing ambient temperature and relative humidity, were central to keeping energy budgets balanced in both populations. While bats’ metabolic rate during torpor and rest did not differ between roosts, adjusting torpor frequency, duration and timing helped bats maintain body condition. Interestingly, the exposed forest roost induced extensive use of torpor, which exceeded the torpor frequency of overwintering bats that stayed in the cave for months and consequently minimised daytime resting energy expenditure in the forest. Our current understanding of intraspecific physiological variation is limited and physiological traits are often considered to be fixed. The results of our study therefore highlight the need for examining species at broad environmental scales to avoid underestimating a species’ full capacity for withstanding environmental variation, especially in the face of ongoing, disruptive human interference in natural habitats.

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Body Temperature and Activity Rhythms Under Different Photoperiods in High Arctic Svalbard ptarmigan (Lagopus muta hyperborea)

Cited by 8 publications

References 43 publications

Modified Wavelet Analyses Permit Quantification of Dynamic Interactions Between Ultradian and Circadian Rhythms

Modified Wavelet Analyses Permit Quantification of Dynamic Interactions Between Ultradian and Circadian Rhythms

Seasonality in Biological Rhythms in Scandinavian brown Bears

Disparate roost sites drive intraspecific physiological variation in a Malagasy bat

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