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Geiser F, Ruf T. Long-term survival, temperature, and torpor patterns. Sci Rep 2023; 13:6673. [PMID: 37095170 PMCID: PMC10126141 DOI: 10.1038/s41598-023-33646-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 04/17/2023] [Indexed: 04/26/2023] Open
Abstract
Mammalian and avian torpor is highly effective in reducing energy expenditure. However, the extent of energy savings achieved and thus long-term survival appear to differ between species capable of multiday hibernation and species restricted to daily heterothermy, which could, however, be due to thermal effects. We tested how long-term survival on stored body fat (i.e. time to lean body mass), crucial for overcoming adverse periods, is related to the pattern of torpor expressed under different ambient temperatures (Ta: 7 °C typical of hibernation, 15 and 22 °C typical of daily torpor) in the small marsupial hibernator the pygmy-possum (Cercartetus nanus). Possums expressed torpor at all Tas and survived without food for 310 days on average at Ta 7 °C, 195 days at Ta 15 °C, and 127 days at Ta 22 °C. At Ta 7 and 15 °C, torpor bout duration (TBD) increased from < 1-3 to ~ 5-16 days over 2 months, whereas at Ta 22 °C, TBD remained at < 1 to ~ 2 days. At all Tas daily energy use was substantially lower and TBD and survival times of possums much longer (3-12 months) than in daily heterotherms (~ 10 days). Such pronounced differences in torpor patterns and survival times even under similar thermal conditions provide strong support for the concept that torpor in hibernators and daily heterotherms are physiologically distinct and have evolved for different ecological purposes.
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Affiliation(s)
- Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, 2351, Australia
| | - Thomas Ruf
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Savoyenstrasse 1, 1160, Vienna, Austria.
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2
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Pronounced differences in heart rate and metabolism distinguish daily torpor and short-term hibernation in two bat species. Sci Rep 2022; 12:21721. [PMID: 36522368 PMCID: PMC9755216 DOI: 10.1038/s41598-022-25590-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 12/01/2022] [Indexed: 12/23/2022] Open
Abstract
Torpor, and its differential expression, is essential to the survival of many mammals and birds. Physiological characteristics of torpor appear to vary between those species that express strict daily heterothermy and those capable of multiday hibernation, but comparisons are complicated by the temperature-dependence of variables. Previous reviews have compared these different torpor strategies by measuring the depth and duration of torpor in multiple species. However, direct comparison of multiple physiological parameters under similar thermal conditions are lacking. Here, we quantified three physiological variables; body temperature, metabolic rate (MR) and heart rate (HR) of two small heterothermic bats (daily heterotherm Syconycteris australis, and hibernator Nyctophilus gouldi) under comparable thermal conditions and torpor bout durations. When normothermic and resting both MR and HR were similar for the two species. However, during torpor the minimum HR was more than fivefold higher, and minimum MR was 6.5-fold higher for the daily heterotherm than for the hibernator at the same subcutaneous Tb (16 ± 0.5 °C). The data show that the degree of heterothermy defined using Tb is not necessarily a precise proxy for physiological capacity during torpor in these bats and is unlikely to reveal accurate energy budgets. Our study provides evidence supporting a distinction between daily torpor in a daily heterotherm and short term torpor in a hibernator, at least within the Chiroptera with regard to these physiological variables. This exists even when individuals display the same degree of Tb reduction, which has clear implications for the modelling of their energy expenditure.
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Sørås R, Fjelldal MA, Bech C, van der Kooij J, Skåra KH, Eldegard K, Stawski C. State dependence of arousal from torpor in brown long-eared bats (Plecotus auritus). J Comp Physiol B 2022; 192:815-827. [PMID: 35972527 PMCID: PMC9550697 DOI: 10.1007/s00360-022-01451-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 06/08/2022] [Accepted: 07/19/2022] [Indexed: 11/02/2022]
Abstract
To cope with periods of low food availability and unsuitable environmental conditions (e.g., short photoperiod or challenging weather), many heterothermic mammals can readily go into torpor to save energy. However, torpor also entails several potential costs, and quantitative energetics can, therefore, be influenced by the individual state, such as available energy reserves. We studied the thermal energetics of brown long-eared bats (Plecotus auritus) in the northern part of its distributional range, including torpor entry, thermoregulatory ability during torpor and how they responded metabolically to an increasing ambient temperature (Ta) during arousal from torpor. Torpor entry occurred later in bats with higher body mass (Mb). During torpor, only 10 out of 21 bats increased oxygen consumption (V̇O2) to a greater extent above the mean torpor metabolic rates (TMR) when exposed to low Ta. The slope of the torpid thermoregulatory curve was shallower than that of resting metabolic rate (RMR) during normothermic conditions, indicating a higher thermal insulation during torpor. During exposure to an increasing Ta, all bats increased metabolic rate exponentially, but the bats with higher Mb aroused at a lower Ta than those with lower Mb. In bats with low Mb, arousal was postponed to an Ta above the lower critical temperature of the thermoneutral zone. Our results demonstrate that physiological traits, which are often considered fixed, can be more flexible than previously assumed and vary with individual state. Thus, future studies of thermal physiology should to a greater extent take individual state-dependent effects into account.
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Affiliation(s)
- Rune Sørås
- Department of Biology, Norwegian University of Science and Technology, 7491, Trondheim, NO, Norway.
| | - Mari Aas Fjelldal
- Department of Biology, Norwegian University of Science and Technology, 7491, Trondheim, NO, Norway
| | - Claus Bech
- Department of Biology, Norwegian University of Science and Technology, 7491, Trondheim, NO, Norway
| | - Jeroen van der Kooij
- Nature Education, Research and Consultancy van der Kooij, Rudsteinveien 67, 1480, Slattum, NO, Norway
| | - Karoline H Skåra
- Department of Biology, Norwegian University of Science and Technology, 7491, Trondheim, NO, Norway
- Centre for Fertility and Health, Norwegian Institute of Public Health, Skøyen, P.O. Box 222, Oslo, 0213, NO, Norway
| | - Katrine Eldegard
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Box 5003, 1433, Ås, NO, Norway
| | - Clare Stawski
- Department of Biology, Norwegian University of Science and Technology, 7491, Trondheim, NO, Norway
- School of Science, Technology and Engineering, University of the Sunshine Coast, Maroochydore DC, QLD, 4558, Australia
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Flexible energy-saving strategies in female temperate-zone bats. J Comp Physiol B 2022; 192:805-814. [PMID: 35939092 PMCID: PMC9550788 DOI: 10.1007/s00360-022-01452-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 07/06/2022] [Accepted: 07/19/2022] [Indexed: 12/02/2022]
Abstract
Torpor is characterized by an extreme reduction in metabolism and a common energy-saving strategy of heterothermic animals. Torpor is often associated with cold temperatures, but in the last decades, more diverse and flexible forms of torpor have been described. For example, tropical bat species maintain a low metabolism and heart rate at high ambient and body temperatures. We investigated whether bats (Nyctalus noctula) from the cooler temperate European regions also show this form of torpor with metabolic inhibition at high body temperatures, and whether this would be as pronounced in reproductive as in non-reproductive bats. We simultaneously measured metabolic rate, heart rate, and skin temperature in non-reproductive and pregnant females at a range of ambient temperatures. We found that they can decouple metabolic rate and heart rate from body temperature: they maintained an extremely low metabolism and heart rate when exposed to ambient temperatures changing from 0 to 32.5 °C, irrespective of reproductive status. When we simulated natural temperature conditions, all non-reproductive bats used torpor throughout the experiment. Pregnant bats used variable strategies from torpor, to maintaining normothermy, or a combination of both. Even a short torpor bout during the day saved up to 33% of the bats' total energy expenditure. Especially at higher temperatures, heart rate was a much better predictor of metabolic rate than skin temperature. We suggest that the capability to flexibly save energy across a range of ambient temperatures within and between reproductive states may be an important ability of these bats and possibly other temperate-zone heterotherms.
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Irving AT, Zhang Q, Kong PS, Luko K, Rozario P, Wen M, Zhu F, Zhou P, Ng JHJ, Sobota RM, Wang LF. Interferon Regulatory Factors IRF1 and IRF7 Directly Regulate Gene Expression in Bats in Response to Viral Infection. Cell Rep 2020; 33:108345. [PMID: 33147460 PMCID: PMC8755441 DOI: 10.1016/j.celrep.2020.108345] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 08/23/2020] [Accepted: 10/13/2020] [Indexed: 12/15/2022] Open
Abstract
Bat cells and tissue have elevated basal expression levels of antiviral genes commonly associated with interferon alpha (IFNα) signaling. Here, we show Interferon Regulatory Factor 1 (IRF1), 3, and 7 levels are elevated in most bat tissues and that, basally, IRFs contribute to the expression of type I IFN ligands and high expression of interferon regulated genes (IRGs). CRISPR knockout (KO) of IRF 1/3/7 in cells reveals distinct subsets of genes affected by each IRF in an IFN-ligand signaling-dependent and largely independent manner. As the master regulators of innate immunity, the IRFs control the kinetics and maintenance of the IRG response and play essential roles in response to influenza A virus (IAV), herpes simplex virus 1 (HSV-1), Melaka virus/Pteropine orthoreovirus 3 Melaka (PRV3M), and Middle East respiratory syndrome-related coronavirus (MERS-CoV) infection. With its differential expression in bats compared to that in humans, this highlights a critical role for basal IRF expression in viral responses and potentially immune cell development in bats with relevance for IRF function in human biology.
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Affiliation(s)
- Aaron T Irving
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore; Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Zhejiang University International Campus, Haining, China; Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
| | - Qian Zhang
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore; University of Chinese Academy of Sciences, Beijing, China; Key Laboratory of Special Pathogens, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Pui-San Kong
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore
| | - Katarina Luko
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore
| | - Pritisha Rozario
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore
| | - Ming Wen
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore
| | - Feng Zhu
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore
| | - Peng Zhou
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore; Key Laboratory of Special Pathogens, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Justin H J Ng
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore
| | - Radoslaw M Sobota
- Functional Proteomics Laboratory, Institute of Molecular and Cell Biology (A(∗)STAR), Singapore, Singapore; Institute of Medical Biology (IMB), Agency for Science, Technology and Research (A(∗)STAR), Singapore, Singapore
| | - Lin-Fa Wang
- Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore.
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Horowitz BN, Kutinsky IB, Linde A. Species-Spanning Echocardiography: Cardiovascular Insights from Across the Animal Kingdom. Curr Cardiol Rep 2020; 22:165. [PMID: 33037937 DOI: 10.1007/s11886-020-01417-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/03/2020] [Indexed: 10/23/2022]
Abstract
PURPOSE OF REVIEW The objective of this review is to present comparative echocardiography as a source of insights for human cardiovascular medicine. RECENT FINDINGS We present echocardiographic examples of high impact human cardiovascular pathologies, including valvular, vascular, conduction, and myocardial disorders, in a wide range of species in varying environments. Unique features associated with comparative echocardiographic assessments are linked to human cardiology, including natural animal models of resistance and vulnerability. The cardiovascular vulnerabilities and strengths of other species can be a source of invaluable insights for human healthcare professionals. Echocardiography is playing a key role in bridging human and veterinary cardiology. Consequently, species-spanning echocardiography can deliver novel insights for human medicine.
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Affiliation(s)
- B N Horowitz
- Department of Medicine, Harvard Medical School, Boston, MA, USA. .,Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA. .,David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
| | - Ilana B Kutinsky
- William Beaumont School of Medicine, Oakland University, Rochester, MI, USA
| | - Annika Linde
- College of Veterinary Medicine, Western University of Health Sciences, Pomona, CA, USA
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Martínková N, Baird SJE, Káňa V, Zima J. Bat population recoveries give insight into clustering strategies during hibernation. Front Zool 2020; 17:26. [PMID: 32884575 PMCID: PMC7465407 DOI: 10.1186/s12983-020-00370-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 08/13/2020] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND Behaviour during hibernation contributes to energy conservation in winter. Hibernating bats select roosts with respect to physiological and environmental stressors, available local microclimate and species-specific requirements. RESULTS We found that, in the period between 1977 and 2018, hibernating Myotis myotis and Rhinolophus hipposideros bats showed exponential population growth. The growth rates, corrected for local winter seasonal severity and winter duration, were equal to 10 and 13%, respectively. While R. hipposideros only utilised the thermally stable and, at survey time, warmer corridors in the hibernaculum, an increasing proportion of M. myotis roosted in the thermally stable corridors as their abundance increased. About 14% of all hibernating M. myotis displayed solitary roosting, irrespective of other covariates. Those bats that clustered together formed progressively larger clusters with increasing abundance, particularly in cold corridors. We found no statistically significant relationship for clustering behaviour or cluster size with winter severity or winter duration. CONCLUSIONS Abundance of hibernating bats is increasing in Central Europe. As the number of M. myotis bats increases, thermally unstable corridors become saturated with large clusters and the animals begin to roost deeper underground.
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Affiliation(s)
- Natália Martínková
- Institute of Vertebrate Biology, Czech Academy of Sciences, Květná 8, Brno, 60365 Czechia
- RECETOX, Masaryk University, Kamenice 753/5, Brno, 62500 Czechia
| | - Stuart J. E. Baird
- Institute of Vertebrate Biology, Czech Academy of Sciences, Květná 8, Brno, 60365 Czechia
| | | | - Jan Zima
- Institute of Vertebrate Biology, Czech Academy of Sciences, Květná 8, Brno, 60365 Czechia
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Duda N, Ripperger S, Tschapka M, Mayer F, Weigel R, Koelpin A. Wireless Sensor Platform for Detection of Vital Parameters of Bats. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2019:1294-1297. [PMID: 31946129 DOI: 10.1109/embc.2019.8856769] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In this paper an advanced sensor node for animal tracking is proposed, which includes an accelerometer, an air pressure sensor as well as an electrocardiography sensor. The system is designed for studying the physiology and behavior of bats by inferring activity, wing beat frequency as well as heart rate. This system offers outstanding functionality compared to other tracking nodes and is easily applicable thanks to its noninvasive design. Gluing the sensor to the bat's back keeps the impact on the animal at a minimum and retrieval of the animal to remove the tag is not required since the tag falls off after a few days.
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Irving AT, Ng JHJ, Boyd V, Dutertre C, Ginhoux F, Dekkers MH, Meers J, Field HE, Crameri G, Wang L. Optimizing dissection, sample collection and cell isolation protocols for frugivorous bats. Methods Ecol Evol 2019. [DOI: 10.1111/2041-210x.13325] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Aaron T. Irving
- Programme in Emerging Infectious Diseases Duke‐NUS Medical School Singapore
| | - Justin H. J. Ng
- Programme in Emerging Infectious Diseases Duke‐NUS Medical School Singapore
| | - Victoria Boyd
- Australian Animal Health Laboratory, Health and Biosecurity Business Unit Commonwealth Scientific and Industrial Research Organisation Geelong Vic Australia
| | - Charles‐Antoine Dutertre
- Programme in Emerging Infectious Diseases Duke‐NUS Medical School Singapore
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore Singapore
| | - Florent Ginhoux
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore Singapore
| | - Milou H. Dekkers
- Queensland Animal Science Precinct The University of Queensland Gatton QLD Australia
| | - Joanne Meers
- School of Veterinary Science The University of Queensland Gatton QLD Australia
| | - Hume E. Field
- School of Veterinary Science The University of Queensland Gatton QLD Australia
- EcoHealth Alliance New York NY USA
| | - Gary Crameri
- Crameri Research Consulting Geelong Vic Australia
| | - Lin‐Fa Wang
- Programme in Emerging Infectious Diseases Duke‐NUS Medical School Singapore
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Currie SE, Mène-Saffrané L, Fasel NJ. Valuable carcasses: postmortem preservation of fatty acid composition in heart tissue. CONSERVATION PHYSIOLOGY 2019; 7:coz005. [PMID: 30805190 PMCID: PMC6382032 DOI: 10.1093/conphys/coz005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 12/04/2018] [Accepted: 01/23/2019] [Indexed: 06/09/2023]
Abstract
In order to effectively conserve species, we must understand the structure and function of integral mechanisms at all levels of organismal organisation, from intracellular biochemistry to whole animal ecophysiology. The accuracy of biochemical analyses depend on the quality and integrity of the samples analysed. It is believed that tissue samples collected immediately postmortem provide the most reliable depiction of the living animal. Yet, euthanasia of threatened or protected species for the collection of tissue presents a number of ethical complications. Polyunsaturated fatty acids (PUFA) are essential to the cardiovascular system of all animals and the structure of PUFA can be degraded by peroxidation, potentially modifying the fatty acid composition of the tissue over postmortem time. Here, we assessed the composition of PUFA in cardiac tissue of bats (Carollia perspicillata) over the course of 12-h postmortem. We show that PUFA are resistant to naturally occurring postmortem degradation in heart tissue, with no difference in the overall composition of fatty acids across all time classes (0, 3, 6 or 12-h postmortem). Our results suggest that carcasses that would otherwise be discarded may actually be viable for the assessment of fatty acid composition in a number of tissues. We hope to spur further investigations into the viability of carcasses for other biochemical analyses as they may be an untapped resource available to biologists.
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Affiliation(s)
- Shannon E Currie
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Alfred Kowalke Str. 17, Berlin, Germany
| | - Laurent Mène-Saffrané
- Department of Biology, University of Fribourg, Chemin du Musée 10, Fribourg, Switzerland
- Metabolomics and Proteomics Platform, University of Fribourg, Chemin du Musée 10, Fribourg, Switzerland
| | - Nicolas J Fasel
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Alfred Kowalke Str. 17, Berlin, Germany
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Geiser F, Bondarenco A, Currie SE, Doty AC, Körtner G, Law BS, Pavey CR, Riek A, Stawski C, Turbill C, Willis CKR, Brigham RM. Hibernation and daily torpor in Australian and New Zealand bats: does the climate zone matter? AUST J ZOOL 2019. [DOI: 10.1071/zo20025] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We aim to summarise what is known about torpor use and patterns in Australian and New Zealand (ANZ) bats from temperate, tropical/subtropical and arid/semiarid regions and to identify whether and how they differ. ANZ bats comprise ~90 species from 10 families. Members of at least nine of these are known to use torpor, but detailed knowledge is currently restricted to the pteropodids, molossids, mystacinids, and vespertilionids. In temperate areas, several species can hibernate (use a sequence of multiday torpor bouts) in trees or caves mostly during winter and continue to use short bouts of torpor for the rest of the year, including while reproducing. Subtropical vespertilionids also use multiday torpor in winter and brief bouts of torpor in summer, which permit a reduction in foraging, probably in part to avoid predators. Like temperate-zone vespertilionids they show little or no seasonal change in thermal energetics during torpor, and observed changes in torpor patterns in the wild appear largely due to temperature effects. In contrast, subtropical blossom-bats (pteropodids) exhibit more pronounced daily torpor in summer than winter related to nectar availability, and this involves a seasonal change in physiology. Even in tropical areas, vespertilionids express short bouts of torpor lasting ~5 h in winter; summer data are not available. In the arid zone, molossids and vespertilionids use torpor throughout the year, including during desert heat waves. Given the same thermal conditions, torpor bouts in desert bats are longer in summer than in winter, probably to minimise water loss. Thus, torpor in ANZ bats is used by members of all or most families over the entire region, its regional and seasonal expression is often not pronounced or as expected, and it plays a key role in energy and water balance and other crucial biological functions that enhance long-term survival by individuals.
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Currie SE. No effect of season on the electrocardiogram of long-eared bats (Nyctophilus gouldi) during torpor. J Comp Physiol B 2018; 188:695-705. [PMID: 29623413 DOI: 10.1007/s00360-018-1158-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 03/27/2018] [Accepted: 04/01/2018] [Indexed: 01/23/2023]
Abstract
Heterothermic animals regularly undergo profound alterations of cardiac function associated with torpor. These animals have specialised tissues capable of withstanding fluctuations in body temperature > 30 °C without adverse effects. In particular, the hearts of heterotherms are able to resist fibrillation and discontinuity of the cardiac conduction system common in homeotherms during hypothermia. To investigate the patterns of cardiac conduction in small insectivorous bats which enter torpor year round, I simultaneously measured ECG and subcutaneous temperature (Tsub) of 21 Nyctophilus gouldi (11 g) during torpor at a range of ambient temperatures (Ta 1-28 °C). During torpor cardiac conduction slowed in a temperature dependent manner, primarily via prolongation along the atrioventricular pathway (PR interval). A close coupling of depolarisation and repolarisation was retained in torpid bats, with no isoelectric ST segment visible until animals reached Tsub <6 °C. There was little change in ventricular repolarisation (JT interval) with decreasing Tsub, or between rest and torpor at mild Ta. Bats retained a more rapid rate of ventricular conduction and repolarisation during torpor relative to other hibernators. Throughout all recordings across seasons (> 2500 h), there was no difference in ECG morphology or heart rate during torpor, and no manifestations of significant conduction blocks or ventricular tachyarrhythmias were observed. My results demonstrate the capacity of bat hearts to withstand extreme fluctuations in rate and temperature throughout the year without detrimental arrhythmogenesis. I suggest that this conduction reserve may be related to flight and the daily extremes in metabolism experienced by these animals, and warrants further investigation of cardiac electrophysiology in other flying hibernators.
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Affiliation(s)
- Shannon E Currie
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia. .,Department of Zoology, Faculty of Life Sciences, Tel Aviv University, P.O. Box 39040, Tel Aviv, 6997801, Israel.
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