The metabolic cost of subcutaneous and abdominal rewarming in king penguins after long-term immersion in cold water

Lewden, Agnès; Bonnet, Batshéva; Nord, Andreas

doi:10.1016/j.jtherbio.2020.102638

Cited by 5 publications

(6 citation statements)

References 21 publications

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“…willow ptarmigan Lagopus lagopus , ducks and gulls) have thicker dermal scales to insulate their feet and legs to minimize heat loss (Swaddle & Witter, 1994; Duchamp & Barre, 1993; Stevens et al ., 1986). Polar birds such as penguins, snowy owl ( Bubo scandiacus ) and willow ptarmigan protect themselves physically against the cold by growing a winter plumage or by relying on a layer of fat, somewhat similar to blubber (Lewden, Bonnet & Nord, 2020; Blix, 2016). Svalbard ptarmigan ( Lagopus muta hyperborea ) store up to 35% of their body mass as fat in preparation for winter (Stokkan, 1992).…”

Section: Cold Adaptationmentioning

confidence: 99%

Avian adjustments to cold and non‐shivering thermogenesis: whats, wheres and hows

Pani

Bal

2022

Biological Reviews

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Avian cold adaptation is hallmarked by innovative strategies of both heat conservation and thermogenesis. While minimizing heat loss can reduce the thermogenic demands of body temperature maintenance, it cannot eliminate the requirement for thermogenesis. Shivering and non-shivering thermogenesis (NST) are the two synergistic mechanisms contributing to endothermy. Birds are of particular interest in studies of NST as they lack brown adipose tissue (BAT), the major organ of NST in mammals. Critical analysis of the existing literature on avian strategies of cold adaptation suggests that skeletal muscle is the principal site of NST. Despite recent progress, isolating the mechanisms involved in avian muscle NST has been difficult as shivering and NST co-exist with its primary locomotory function. Herein, we re-evaluate various proposed molecular bases of avian skeletal muscle NST. Experimental evidence suggests that sarco(endo)plasmic reticulum Ca 2+ -ATPase (SERCA) and ryanodine receptor 1 (RyR1) are key in avian muscle NST, through their mediation of futile Ca 2+ cycling and thermogenesis. More recent studies have shown that SERCA regulation by sarcolipin (SLN) facilitates muscle NST in mammals; however, its role in birds is unclear. Ca 2+ signalling in the muscle seems to be common to contraction, shivering and NST, but elucidating its roles will require more precise measurement of local Ca 2+ levels inside avian myofibres. The endocrine control of avian muscle NST is still poorly defined. A better understanding of the mechanistic details of avian muscle NST will provide insights into the roles of these processes in regulatory thermogenesis, which could further inform our understanding of the evolution of endothermy among vertebrates.

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Section: Cold Adaptationmentioning

confidence: 99%

Avian adjustments to cold and non‐shivering thermogenesis: whats, wheres and hows

Pani

Bal

2022

Biological Reviews

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“…For a comparison of methods to assign chronotype from skin temperature, we surveyed previous applications of identifying changepoints (here, onset and offset) in various types of time series that showed similar curve characteristics (i.e., increases and/or decreases) as seen in temporal patterns of diel body temperature [52] but also of torpor [51,62], seasonal and diel activity [29,30,60] and moulting [63]. We identified three approaches useful to our study.…”

Section: Chronotype Estimates From Skin Temperaturementioning

confidence: 99%

“…The remaining nine filtered-out individuals with zero diel days are not shown. Two additional individuals (marked in bold font) were excluded from the chronotype analyses as they did not fulfil all selection criteria (173.391 M had no positive autocorrelation at 24 on segmented linear regressions (as in [52,60]), whereby one (Broken Stick Regression) fits a single changepoint of slopes [51], whereas the second (Structural Changes) generates multiple changepoints of slopes, from which an optimal changepoint can be selected. A third approach estimates changepoints from distributions (Behavioural Changepoint Analyses, BCPA, by [29]), whereby multiple changepoints are generated, and the one that results in the best model fit is selected.…”

Section: Chronotype Estimates From Skin Temperaturementioning

confidence: 99%

“…Various R packages are available to extract these changepoints. For the Broken Stick Regression we chose the lm.br function (from lm.br package by Adams 2021 based on [64]) used in Lewden et al [51]. Different type settings (i.e., line-line, threshold-line, line-threshold) can be adjusted and applied in combination with a selected analysis window depending on the customer's needs.…”

Section: Chronotype Estimates From Skin Temperaturementioning

confidence: 99%

“…Furthermore, curves can deviate considerably from standard models, for example for activity by sudden shifts, or for body temperature by a spectrum from sinusoidal curves to time series with plateaus [6,10,49,50]. Therefore, many studies use generic procedures, such as visual data extraction [24] or employ changepoint analyses to extract phase markers of interest in their specific type of data [29,51,52]. Depending on the research question and the data available, changepoints can be assigned based on moving averages or on changes in variation between subsequent data points.…”

Section: Introductionmentioning

confidence: 99%

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Using skin temperature and activity profiles to assign chronotype in birds

et al. 2022

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Chronotypes describe consistent differences between individuals in biological time-keeping. They have been linked both with underlying variation in the circadian system and fitness. Quantification of chronotypes is usually by time of onset, midpoint, or offset of a rhythmic behaviour or physiological process. However, diel activity patterns respond flexibly to many short-term environmental influences, which can make chronotypes hard to identify. In contrast, rhythmic patterns in physiological processes, such as body temperature, may provide more robust insights into the circadian basis of chronotypes. These can be telemetrically recorded from skin-mounted, temperature-sensitive transmitters, offering minimally invasive opportunities for working on free-ranging animals in the wild. Currently, computational methods for deriving chronotype from skin temperature require further development, as time series are often noisy and incomplete. Here, we investigate such methods using simultaneous radio telemetry recordings of activity and skin temperature in a wild songbird model (Great Tit Parus major) temporarily kept in outdoor aviaries. Our aims were to first develop standardised selection criteria to filter noisy time series of skin temperature and activity, to second assign chronotype based on the filtered recordings, and to third compare chronotype as assigned based on each of the two rhythms. After the selection of rhythmic data using periodicity and autocorrelation parameters, chronotype estimates (onset and offset) were extracted using four different changepoint approaches for skin temperature and one approach for activity records. The estimates based on skin temperature varied between different approaches but were correlated to each other (onset: correlation coefficient r = 0.099–0.841, offset: r = 0.131–0.906). In contrast, chronotype estimates from skin temperature were more weakly correlated to those from activity (onset: r = −0.131–0.612, offset: r = −0.040– −0.681). Overall, chronotype estimates were less variable and timed later in the day for activity than for skin temperature. The distinctions between physiological and behavioural chronotypes in this study might reflect differences in underlying mechanisms and in responsiveness to external and internal cues. Thus, studying each of these rhythms has specific strengths, while parallel studies of both could inform broadly on natural variation in biological time-keeping, and may allow assessment of how biological rhythms relate to changes in the environment.

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Body surface rewarming in fully and partially hypothermic king penguins

et al. 2020

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Penguins face a major thermal transition when returning to land in a hypothermic state after a foraging trip. Uninsulated appendages (flippers and feet) could provide flexible heat exchange during subsequent rewarming. Here, we tested the hypothesis that peripheral vasodilation could be delayed during this recovery stage. To this end, we designed an experiment to examine patterns of surface rewarming in fully hypothermic (the cloaca and peripheral regions (here; flippers, feet and the breast) < 37 °C) and partially hypothermic (cloaca at normothermia ≥ 37 °C, but periphery at hypothermia) king penguins (Aptenodytes patagonicus) when they rewarmed in the laboratory. Both groups rewarmed during the 21 min observation period, but the temperature changes were larger in fully than in partially hypothermic birds. Moreover, we observed a 5 min delay of peripheral temperature in fully compared to partially hypothermic birds, suggesting that this process was impacted by low internal temperature. To investigate whether our laboratory data were applicable to field conditions, we also recorded surface temperatures of free-ranging penguins after they came ashore to the colony. Initial surface temperatures were lower in these birds compared to in those that rewarmed in the laboratory, and changed less over a comparable period of time on land. This could be explained both by environmental conditions and possible handling-induced thermogenesis in the laboratory. Nevertheless, this study demonstrated that appendage vasodilation is flexibly used during rewarming and that recovery may be influenced by both internal temperature and environmental conditions when penguins transition from sea to land.

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The metabolic cost of subcutaneous and abdominal rewarming in king penguins after long-term immersion in cold water

Cited by 5 publications

References 21 publications

Avian adjustments to cold and non‐shivering thermogenesis: whats, wheres and hows

Avian adjustments to cold and non‐shivering thermogenesis: whats, wheres and hows

Using skin temperature and activity profiles to assign chronotype in birds

Body surface rewarming in fully and partially hypothermic king penguins

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