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Martin Jastroch, Sylvain Giroud, Perry Barrett, Fritz Geiser, Gerhard Heldmaier, Annika Herwig
Endothermic mammals and birds require intensive energy turnover to sustain high body temperatures and metabolic rates. To cope with energetic bottlenecks associated with the change of seasons, and to minimise energy expenditure, complex mechanisms and strategies, such as daily torpor and hibernation, are used. During torpor metabolic depression and low body temperatures save energy. However, these bouts of torpor lasting for hours to weeks are interrupted by active 'euthermic' phases with high body temperatures...
October 18, 2016: Journal of Neuroendocrinology
Jaya K Matthews, Clare Stawski, Gerhard Körtner, Cassandra A Parker, Fritz Geiser
Wildfires can completely obliterate above-ground vegetation, yet some small terrestrial mammals survive during and after fires. As knowledge about the physiological and behavioural adaptations that are crucial for post-wildfire survival is scant, we investigated the thermal biology of a small insectivorous marsupial (Antechinus flavipes) after a severe forest fire. Some populations of antechinus survived the fire in situ probably by hiding deep in rocky crevices, the only fire-proof sites near where they were trapped...
October 12, 2016: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
Kathrin H Dausmann, Lisa Warnecke
Torpor, the controlled depression of virtually all bodily function during scarce periods, was verified in primates under free-ranging conditions less than two decades ago. The large variety of different torpor patterns found both within and among closely related species is particularly remarkable. To help unravel the cause of these variable patterns, our review investigates primate torpor use within an evolutionary framework. First, we provide an overview of heterothermic primate species, focusing on the Malagasy lemurs, and discuss their use of daily torpor or hibernation in relation to habitat type and climatic conditions...
November 1, 2016: Physiology
Theodore J Weller, Kevin T Castle, Felix Liechti, Cris D Hein, Michael R Schirmacher, Paul M Cryan
Understanding of migration in small bats has been constrained by limitations of techniques that were labor-intensive, provided coarse levels of resolution, or were limited to population-level inferences. Knowledge of movements and behaviors of individual bats have been unknowable because of limitations in size of tracking devices and methods to attach them for long periods. We used sutures to attach miniature global positioning system (GPS) tags and data loggers that recorded light levels, activity, and temperature to male hoary bats (Lasiurus cinereus)...
October 4, 2016: Scientific Reports
Vijay Kumar Saxena, Davendra Kumar, S M K Naqvi
GPR50, formerly known as a melatonin-related receptor, is one of the three subtypes of melatonin receptor subfamily, together with MTNR1A and MTNR1B. GPR50, despite its high identity with the melatonin receptor family, does not bind melatonin and is considered to be an ortholog of MTNR1C in mammals. GPR50-expressing cells have been found in the dorsomedial nucleus of the hypothalamus, the periventricular nucleus, and the median eminence. Genetic and functional evidence have been recently investigated linking GPR50 to adaptive thermogenesis and torpor, but still, it is an orphan receptor and is yet to be studied conclusively...
September 27, 2016: International Journal of Biometeorology
Heiko T Jansen, Tanya Leise, Gordon Stenhouse, Karine Pigeon, Wayne Kasworm, Justin Teisberg, Thomas Radandt, Robert Dallmann, Steven Brown, Charles T Robbins
BACKGROUND: Most biological functions are synchronized to the environmental light:dark cycle via a circadian timekeeping system. Bears exhibit shallow torpor combined with metabolic suppression during winter dormancy. We sought to confirm that free-running circadian rhythms of body temperature (Tb) and activity were expressed in torpid grizzly (brown) bears and that they were functionally responsive to environmental light. We also measured activity and ambient light exposures in denning wild bears to determine if rhythms were evident and what the photic conditions of their natural dens were...
2016: Frontiers in Zoology
James M Turner, Fritz Geiser
Many mammals use torpor throughout the year but the individual contributions of environmental variables to seasonal changes in torpor expression are often difficult to tease apart. In many mammals, torpor is most often used opportunistically in response to decreased ambient temperature (T a ) and food availability, but information on how seasonally changing photoperiod per se influences torpor patterns is scant. Therefore, we quantified patterns of torpor use in response to natural photoperiod in captive marsupial pygmy-possums held at near-constant T a with a stable food supply over a period of 19 months...
September 16, 2016: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
A A Lakhina, L N Markevich, N M Zakharova, V N Afanasyev, I K Kolomiytseva, E E Fesenko
In hibernating Yakutian ground squirrels S. undulatus, the content of total phospholipids in the nuclei of liver increased by 40% compared to that in animals in summer. In torpid state, the amount of sphingomyelin increased almost 8 times; phosphatidylserine, 7 times; and cardiolipin, 4 times. In active "winter" ground squirrels, the amount of sphingomyelin, phosphatidylserine, and cardiolipin decreased compared to the hibernating individuals but remained high compared to the "summer" ones. The torpor state did not affect the amount of lysophosphatidylcholine and phosphatidylinositol...
July 2016: Doklady. Biochemistry and Biophysics
Yichi Zhang, Shannon N Tessier, Kenneth B Storey
Foxo4 and MyoG proteins regulate the transcription of numerous genes, including the E3 ubiquitin ligases MAFbx and MuRF1, which are activated in skeletal muscle under atrophy-inducing conditions. In the thirteen-lined ground squirrel, there is little muscle wasting that occurs during hibernation, a process characterized by bouts of torpor and arousal, despite virtual inactivity. Consequently, we were interested in studying the regulatory role of Foxo4 and MyoG on ubiquitin ligases throughout torpor-arousal cycles...
October 2016: Cryobiology
Shannon N Tessier, Kenneth B Storey
Signal transduction pathways transmit information received at the cell surface to intracellular targets which direct a response. We highlight the involvement of signaling pathways in mediating transitions between mammalian torpor and euthermia and suggest these promote survival under stressors (e.g., hypothermia, ischemia-reperfusion) that would otherwise cause damage in nonhibernators.
July 2014: Temperature: Multidisciplinary Biomedical Journal
Domenico Tupone, Shaun Morrison
Activation of central adenosine A1 receptors in the rat, a non-hibernating species, mimics the physiological characteristics of torpor and could thus represent a basis for the development of pharmacological approaches to induce therapeutic hypothermia in pathologies such as brain hemorrhage and ischemia, and to facilitate long-term space travel.
July 2014: Temperature: Multidisciplinary Biomedical Journal
Shit F Chew, Kum Hiong
Scientists have long been fascinated by animals undergoing aestivation, a state of torpor at high temperature, due to its great potential in fields ranging from medicine to space travel. The brain of the African lungfish is able to coordinate a whole-body response to induce aestivation and to arouse from aestivation.
July 2014: Temperature: Multidisciplinary Biomedical Journal
Zenon J Czenze, R Mark Brigham, Anthony J R Hickey, Stuart Parsons
Seasonal changes in weather and food availability differentially impact energy budgets of small mammals such as bats. While most thermal physiological research has focused on species that experience extreme seasonal temperature variations, knowledge is lacking from less variable temperate to subtropical climates. We quantified ambient temperature (T a) and skin temperature (T sk) responses by individuals from a population of New Zealand lesser short-tailed bats (Mystacina tuberculata) during summer and winter using temperature telemetry...
August 25, 2016: Oecologia
Julia Nowack, Marine Delesalle, Clare Stawski, Fritz Geiser
Increased habitat fragmentation, global warming and other human activities have caused a rise in the frequency of wildfires worldwide. To reduce the risks of uncontrollable fires, prescribed burns are generally conducted during the colder months of the year, a time when in many mammals torpor is expressed regularly. Torpor is crucial for energy conservation, but the low body temperatures (T b) are associated with a decreased responsiveness and torpid animals might therefore face an increased mortality risk during fires...
October 2016: Die Naturwissenschaften
Justin G Boyles, Liam P McGuire, Esmarie Boyles, Jesika P Reimer, Christopher A C Brooks, Robert W Rutherford, Teresa A Rutherford, John O Whitaker, Gary F McCracken
Widespread animals at the extremes of the species' distribution experience ecological constraints different than individuals in the core of the distribution. For example, small endotherms at very high latitudes face short summers with cool temperatures and a lack of true darkness. In particular, insectivorous bats at high latitudes may experience constraints because of their unique life history traits, and may have different energy requirements than bats at lower latitudes. To evaluate the extent of these differences, we estimated an energy budget and refueling rates for reproductively active female little brown bats (Myotis lucifugus) roosting in buildings in eastern Alaska (~63°N)...
October 15, 2016: Physiology & Behavior
Franz Hoelzl, Jessica S Cornils, Steve Smith, Yoshan Moodley, Thomas Ruf
We studied the impact of hibernation and food supply on relative telomere length (RTL), an indicator for aging and somatic maintenance, in free-living edible dormice. Small hibernators such as dormice have ∼50% higher maximum longevity than non-hibernators. Increased longevity could theoretically be due to prolonged torpor directly slowing cellular damage and RTL shortening. However, although mitosis is arrested in mammals at low body temperatures, recent evidence points to accelerated RTL shortening during periodic re-warming (arousal) from torpor...
August 15, 2016: Journal of Experimental Biology
Anna C Doty, Clare Stawski, Shannon E Currie, Fritz Geiser
Although roost choice in bats has been studied previously, little is known about how opposing roost colours affect the expression of torpor quantitatively. We quantified roost selection and thermoregulation in a captive Australian insectivorous bat, Nyctophilus gouldi (n=12) in winter when roosting in black and white coloured boxes using temperature-telemetry. We quantified how roost choice influences torpor expression when food was provided ad libitum or restricted in bats housed together in an outdoor aviary exposed to natural fluctuations of ambient temperature...
August 2016: Journal of Thermal Biology
Katherine E Mathers, Sarah V McFarlane, Lin Zhao, James F Staples
Small hibernators cycle between periods of torpor, with body temperature (T b) approximately 5 °C, and interbout euthermia (IBE), where T b is approximately 37 °C. During entrance into a torpor bout liver mitochondrial respiration is rapidly suppressed by 70 % relative to IBE. We compared activities of electron transport system (ETS) complexes in intact liver mitochondria isolated from 13-lined ground squirrels (Ictidomys tridecemlineatus) sampled during torpor and IBE to investigate potential sites of this reversible metabolic suppression...
August 6, 2016: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
Kimberly E Miller, Kaitlyn Barr, Mitchell Krawczyk, Ellen Covey
Eptesicus fuscus is typical of temperate zone bats in that both sexes undergo marked seasonal changes in behavior, endocrine status, and reproductive status. Acoustic communication plays a key role in many seasonal behaviors. For example, males emit specialized vocalizations during mating in the fall, and females use different specialized vocalizations to communicate with infants in late spring. Bats of both sexes use echolocation for foraging during times of activity, but engage in little sound-directed behavior during torpor and hibernation in winter...
July 26, 2016: Hearing Research
Gonzalo León-Espinosa, Esther García, Ulises Gómez-Pinedo, Félix Hernández, Javier DeFelipe, Jesús Ávila
Generation of new neurons from adult neural stem cells occurs in the dentate gyrus (DG) of the hippocampus and the lateral walls of the lateral ventricles. In this article, we study the neurogenesis that takes place during the hibernation of the Syrian hamster (Mesocricetus auratus). Using a variety of standard neurogenesis markers and 5-bromo-2-deoxyuridine (BrdU) incorporation, we describe a preferential decrease in the proliferation of newborn neurons in the subventricular zone (SVZ) of the hibernating hamsters (torpor) rather than in the hippocampus...
October 1, 2016: Neuroscience
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