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Voges JJ, Freeman MT, Wolf BO, McKechnie AE. Functional role of metabolic suppression in avian thermoregulation in the heat. J Therm Biol 2024; 123:103924. [PMID: 39089117 DOI: 10.1016/j.jtherbio.2024.103924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 07/10/2024] [Accepted: 07/10/2024] [Indexed: 08/03/2024]
Abstract
Hypometabolism arising from active metabolic suppression occurs in several contexts among endotherms, particularly during heterothermic states such as torpor. However, observed Q10 ≈ 1 for avian resting metabolic rate within the thermoneutral zone, values far below the Q10 = 2-3 expected on the basis of Arrhenius effects, suggests hypometabolism also plays a role in birds' thermoregulation at environmental temperatures approaching or exceeding normothermic body temperature (Tb). We evaluated the occurrence of hypometabolism during heat exposure among birds by re-analysing literature data to quantify changes in Tb and resting metabolic rate (RMR) near the upper boundary of the thermoneutral zone, at air temperatures (Tair) between the inflection above which Tb increases above normothermic levels (Tb.inf) and the upper critical limit of thermoneutrality (Tuc). Among the ∼55 % of species in which Tuc - Tb.inf > 0, Q10 < 2-3 occurred in nine of 10 orders for which suitable data exist, indicating that hypometabolism during heat exposure is widespread across the avian phylogeny. Values of Q10 < 2-3 were not restricted to small body mass, as previously proposed. Our findings support the idea that metabolic suppression reduces avian metabolic heat production and hence evaporative cooling requirements during heat exposure, with reductions of 20-30 % in RMR in some species. Moreover, these findings add to evidence that hypometabolism is an important component of heat tolerance among endotherms such as birds and tropical arboreal mammals.
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Affiliation(s)
- Jochen J Voges
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, 0001, South Africa; DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield, 0028, South Africa
| | - Marc T Freeman
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, 0001, South Africa; DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield, 0028, South Africa
| | - Blair O Wolf
- UNM Biology Department, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Andrew E McKechnie
- South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, Pretoria, 0001, South Africa; DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield, 0028, South Africa.
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2
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von Schmalensee L, Ittonen M, Brødsgaard Shoshan A, Roberts KT, Siemers I, Süess P, Wiklund C, Gotthard K. Methodological artefacts cause counter-intuitive evolutionary conclusions in a simulation study. Ecol Lett 2024; 27:e14439. [PMID: 38863401 DOI: 10.1111/ele.14439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 12/13/2023] [Accepted: 12/22/2023] [Indexed: 06/13/2024]
Abstract
In their simulation study, Garcia-Costoya et al. (2023) conclude that evolutionary constraints might aid populations facing climate change. However, we are concerned that this conclusion is largely a consequence of the simulated temperature variation being too small, and, most importantly, that uneven limitations to standing variation disadvantage unconstrained populations.
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Affiliation(s)
| | - Mats Ittonen
- Department of Zoology, Stockholm University, Stockholm, Sweden
| | | | - Kevin T Roberts
- Department of Zoology, Stockholm University, Stockholm, Sweden
| | | | - Philip Süess
- Department of Zoology, Stockholm University, Stockholm, Sweden
| | | | - Karl Gotthard
- Department of Zoology, Stockholm University, Stockholm, Sweden
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3
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Levesque DL, Breit AM, Brown E, Nowack J, Welman S. Non-Torpid Heterothermy in Mammals: Another Category along the Homeothermy-Hibernation Continuum. Integr Comp Biol 2023; 63:1039-1048. [PMID: 37407285 DOI: 10.1093/icb/icad094] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 06/14/2023] [Accepted: 06/29/2023] [Indexed: 07/07/2023] Open
Abstract
Variability in body temperature is now recognized to be widespread among whole-body endotherms with homeothermy being the exception rather than the norm. A wide range of body temperature patterns exists in extant endotherms, spanning from strict homeothermy, to occasional use of torpor, to deep seasonal hibernation with many points in between. What is often lost in discussions of heterothermy in endotherms are the benefits of variations in body temperature outside of torpor. Endotherms that do not use torpor can still obtain extensive energy and water savings from varying levels of flexibility in normothermic body temperature regulation. Flexibility at higher temperatures (heat storage or facultative hyperthermia) can provide significant water savings, while decreases at cooler temperatures, even outside of torpor, can lower the energetic costs of thermoregulation during rest. We discuss the varying uses of the terms heterothermy, thermolability, and torpor to describe differences in the amplitude of body temperature cycles and advocate for a broader use of the term "heterothermy" to include non-torpid variations in body temperature.
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Affiliation(s)
| | - Ana M Breit
- School of Biology and Ecology, University of Maine, 04469 Orono, ME, USA
| | - Eric Brown
- School of Biology and Ecology, University of Maine, 04469 Orono, ME, USA
| | - Julia Nowack
- School of Biological and Environmental Sciences, Liverpool John Moores University, L3 3AF Liverpool, UK
| | - Shaun Welman
- Department of Zoology, Nelson Mandela University, Gqeberha 6031, South Africa
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4
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Abstract
Bats perform important ecological roles in our ecosystem. However, recent studies have demonstrated that bats are reservoirs of emerging viruses that have spilled over into humans and agricultural animals to cause severe disease. These viruses include Hendra and Nipah paramyxoviruses, Ebola and Marburg filoviruses, and coronaviruses that are closely related to severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and the recently emerged SARS-CoV-2. Intriguingly, bats that are naturally or experimentally infected with these viruses do not show clinical signs of disease. Here we have reviewed ecological, behavioural, and molecular factors that may influence the ability of bats to harbour viruses. We have summarized known zoonotic potential of bat-borne viruses and stress on the need for further studies to better understand the evolutionary relationship between bats and their viruses, along with discovering the intrinsic and external factors that facilitate the successful spillover of viruses from bats.
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Affiliation(s)
- Victoria Gonzalez
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada
- Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
| | - Arinjay Banerjee
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada
- Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada
- Corresponding author
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5
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Czenze ZJ, Smit B, Jaarsveld B, Freeman MT, McKechnie AE. Caves, crevices and cooling capacity: Roost microclimate predicts heat tolerance in bats. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13918] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Zenon J. Czenze
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Pretoria South Africa
| | - Ben Smit
- Department of Zoology and Entomology Rhodes University Makhanda South Africa
| | - Barry Jaarsveld
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Pretoria South Africa
| | - Marc T. Freeman
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Pretoria South Africa
| | - Andrew E. McKechnie
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Pretoria South Africa
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6
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Levesque DL, Nowack J, Boyles JG. Body Temperature Frequency Distributions: A Tool for Assessing Thermal Performance in Endotherms? Front Physiol 2021; 12:760797. [PMID: 34721082 PMCID: PMC8551754 DOI: 10.3389/fphys.2021.760797] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 09/07/2021] [Indexed: 12/25/2022] Open
Abstract
There is increasing recognition that rather than being fully homeothermic, most endotherms display some degree of flexibility in body temperature. However, the degree to which this occurs varies widely from the relatively strict homeothermy in species, such as humans to the dramatic seasonal hibernation seen in Holarctic ground squirrels, to many points in between. To date, attempts to analyse this variability within the framework generated by the study of thermal performance curves have been lacking. We tested if frequency distribution histograms of continuous body temperature measurements could provide a useful analogue to a thermal performance curve in endotherms. We provide examples from mammals displaying a range of thermoregulatory phenotypes, break down continuous core body temperature traces into various components (active and rest phase modes, spreads and skew) and compare these components to hypothetical performance curves. We did not find analogous patterns to ectotherm thermal performance curves, in either full datasets or by breaking body temperature values into more biologically relevant components. Most species had either bimodal or right-skewed (or both) distributions for both active and rest phase body temperatures, indicating a greater capacity for mammals to tolerate body temperatures elevated above the optimal temperatures than commonly assumed. We suggest that while core body temperature distributions may prove useful in generating optimal body temperatures for thermal performance studies and in various ecological applications, they may not be a good means of assessing the shape and breath of thermal performance in endotherms. We also urge researchers to move beyond only using mean body temperatures and to embrace the full variability in both active and resting temperatures in endotherms.
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Affiliation(s)
- D L Levesque
- School of Biology and Ecology, University of Maine, Orono, ME, United States
| | - J Nowack
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, United Kingdom
| | - J G Boyles
- Cooperative Wildlife Research Laboratory, Center for Ecology, and School of Biological Sciences, Southern Illinois University, Carbondale, IL, United States
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7
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Nowack J, Turbill C. Survivable hypothermia or torpor in a wild-living rat: rare insights broaden our understanding of endothermic physiology. J Comp Physiol B 2021; 192:183-192. [PMID: 34668054 PMCID: PMC8817056 DOI: 10.1007/s00360-021-01416-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 09/08/2021] [Accepted: 10/03/2021] [Indexed: 12/16/2022]
Abstract
Maintaining a high and stable body temperature as observed in endothermic mammals and birds is energetically costly. Thus, it is not surprising that we discover more and more heterothermic species that can reduce their energetic needs during energetic bottlenecks through the use of torpor. However, not all heterothermic animals use torpor on a regular basis. Torpor may also be important to an individual’s probability of survival, and hence fitness, when used infrequently. We here report the observation of a single, ~ 5.5 h long hypothermic bout with a decrease in body temperature by 12 °C in the native Australian bush rat (Rattus fuscipes). Our data suggest that bush rats are able to rewarm from a body temperature of 24 °C, albeit with a rewarming rate lower than that expected on the basis of their body mass. Heterothermy, i.e. the ability to withstand and overcome periods of reduced body temperature, is assumed to be an evolutionarily ancestral (plesiomorphic) trait. We thus argue that such rare hypothermic events in species that otherwise appear to be strictly homeothermic could be heterothermic rudiments, i.e. a less derived form of torpor with limited capacity for rewarming. Importantly, observations of rare and extreme thermoregulatory responses by wild animals are more likely to be discovered with long-term data sets and may not only provide valuable insight about the physiological capability of a population, but can also help us to understand the constraints and evolutionary pathways of different phenologies.
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Affiliation(s)
- Julia Nowack
- Hawkesbury Institute for the Environment and School of Science, Western Sydney University, Richmond, NSW, Australia. .,School of Biological and Environmental Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK.
| | - Christopher Turbill
- Hawkesbury Institute for the Environment and School of Science, Western Sydney University, Richmond, NSW, Australia
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8
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Moreira MO, Qu YF, Wiens JJ. Large-scale evolution of body temperatures in land vertebrates. Evol Lett 2021; 5:484-494. [PMID: 34621535 PMCID: PMC8484719 DOI: 10.1002/evl3.249] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 06/25/2021] [Accepted: 07/19/2021] [Indexed: 11/07/2022] Open
Abstract
Body temperature is a crucial variable in animals that affects nearly every aspect of their lives. Here we analyze for the first time largescale patterns in the evolution of body temperatures across terrestrial vertebrates (tetrapods: including amphibians, mammals, birds and other reptiles). Despite the traditional view that endotherms (birds and mammals) have higher body temperatures than ectotherms, we find they are not significantly different. However, rates of body-temperature evolution are significantly different, with lower rates in endotherms than ectotherms, and the highest rates in amphibians. We find that body temperatures show strong phylogenetic signal and conservatism over 350 million years of evolutionary history in tetrapods, and some lineages appear to have retained similar body temperatures over time for hundreds of millions of years. Although body temperatures are often unrelated to climate in tetrapods, we find that body temperatures are significantly related to day-night activity patterns. Specifically, body temperatures are generally higher in diurnal species than nocturnal species, both across ectotherms and, surprisingly, across endotherms also. Overall, our results suggest that body temperatures are significantly linked to phylogeny and diel-activity patterns within and among tetrapod groups, rather than just climate and the endotherm-ectotherm divide.
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Affiliation(s)
- Matthew O Moreira
- Center for Environmental and Marine Studies, Department of Biology University of Aveiro Aveiro Portugal.,Department of Ecology and Evolutionary Biology University of Arizona Tucson Arizona USA
| | - Yan-Fu Qu
- Department of Ecology and Evolutionary Biology University of Arizona Tucson Arizona USA.,Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences Nanjing Normal University Nanjing Jiangsu China
| | - John J Wiens
- Department of Ecology and Evolutionary Biology University of Arizona Tucson Arizona USA
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9
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High Body Temperature is an Unlikely Cause of High Viral Tolerance in Bats. J Wildl Dis 2021; 57:238-241. [PMID: 33635981 DOI: 10.7589/jwd-d-20-00079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 06/17/2020] [Indexed: 11/20/2022]
Abstract
The global SARS-CoV-2 pandemic and the role of bats in zoonotic spillover have renewed interest in the flight-as-fever hypothesis, which posits that high body temperatures experienced by bats during flight contribute to their high viral tolerance. We argue that flight-as-fever is unlikely to explain why bats harbor more viruses than other mammals on the basis of two lines of reasoning. First, flight temperatures reported in the literature overestimate true flight temperatures because of methodologic limitations. Second, body temperatures in bats are only high relative to humans, and not relative to many other mammals. We provide examples of mammals from diverse habitats to show that temperatures in excess of 40 C during activity are quite common in species with lower viral diversity than bats. We caution scientists against stating the flight-as-fever hypothesis as unquestioned truth, as has repeatedly occurred in the popular media in the wake of the SARS-CoV-2 pandemic.
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10
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Reher S, Dausmann KH. Tropical bats counter heat by combining torpor with adaptive hyperthermia. Proc Biol Sci 2021; 288:20202059. [PMID: 33434466 DOI: 10.1098/rspb.2020.2059] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Many tropical mammals are vulnerable to heat because their water budget limits the use of evaporative cooling for heat compensation. Further increasing temperatures and aridity might consequently exceed their thermoregulatory capacities. Here, we describe two novel modes of torpor, a response usually associated with cold or resource bottlenecks, as efficient mechanisms to counter heat. We conducted a field study on the Malagasy bat Macronycteris commersoni resting in foliage during the hot season, unprotected from environmental extremes. On warm days, the bats alternated between remarkably short micro-torpor bouts and normal resting metabolism within a few minutes. On hot days, the bats extended their torpor bouts over the hottest time of the day while tolerating body temperatures up to 42.9°C. Adaptive hyperthermia combined with lowered metabolic heat production from torpor allows higher heat storage from the environment, negates the need for evaporative cooling and thus increases heat tolerance. However, it is a high-risk response as the torpid bats cannot defend body temperature if ambient temperature increases above a critical/lethal threshold. Torpor coupled with hyperthermia and micro-torpor bouts broaden our understanding of the basic principles of thermal physiology and demonstrate how mammals can perform near their upper thermal limits in an increasingly warmer world.
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Affiliation(s)
- Stephanie Reher
- Functional Ecology, Institute of Zoology, Universität Hamburg, Hamburg, Germany
| | - Kathrin H Dausmann
- Functional Ecology, Institute of Zoology, Universität Hamburg, Hamburg, Germany
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11
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Menzies AK, Studd EK, Majchrzak YN, Peers MJL, Boutin S, Dantzer B, Lane JE, McAdam AG, Humphries MM. Body temperature, heart rate, and activity patterns of two boreal homeotherms in winter: Homeostasis, allostasis, and ecological coexistence. Funct Ecol 2020. [DOI: 10.1111/1365-2435.13640] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Allyson K. Menzies
- Department of Natural Resource Sciences McGill University Ste‐Anne‐de‐Bellevue QC Canada
| | - Emily K. Studd
- Department of Natural Resource Sciences McGill University Ste‐Anne‐de‐Bellevue QC Canada
- Department of Biological Sciences University of Alberta Edmonton AB Canada
| | | | | | - Stan Boutin
- Department of Biological Sciences University of Alberta Edmonton AB Canada
| | - Ben Dantzer
- Department of Psychology University of Michigan Ann Arbor MI USA
- Department of Ecology and Evolutionary Biology University of Michigan Ann Arbor MI USA
| | - Jeffrey E. Lane
- Department of Biology University of Saskatchewan Saskatoon SK Canada
| | - Andrew G. McAdam
- Department of Ecology and Evolutionary Biology University of Colorado Boulder CO USA
| | - Murray M. Humphries
- Department of Natural Resource Sciences McGill University Ste‐Anne‐de‐Bellevue QC Canada
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12
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Bonebrake TC, Rezende EL, Bozinovic F. Climate Change and Thermoregulatory Consequences of Activity Time in Mammals. Am Nat 2020; 196:45-56. [PMID: 32552099 DOI: 10.1086/709010] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Activity times structure the thermal environments experienced by organisms. In mammals, species shift from being nocturnal to diurnal and vice versa, but the thermal consequences of variable activity patterns remain largely unexplored. Here we used theoretical thermoregulatory polygons bounded by estimates of basal metabolic rates (BMR), maximum metabolic rates (MMR), and thermal conductance (C) in small mammals to explore the metabolic consequences of exposure to global-scale daytime and nighttime temperatures. Model predictions indicated higher metabolic scope for activity for nocturnal species at low latitudes and that reduced minimum C and larger body size increased the geographic range in which nocturnality was advantageous. Consistent with predictions, within rodents nocturnal species have low C. However, nocturnal mammals tend to be smaller than diurnal species, likely reflecting the importance of additional factors driving body size. Projections of warming impacts on small mammals suggest that diurnal species could lose habitable space globally. Conversely, warming could lift cool temperature constraints on nocturnal species and increase habitable space, suggesting that a shift toward nocturnal niches might be favored in a warming world. Taken together, these findings demonstrate the importance of energetic considerations for endotherms in managing global change impacts on nocturnal and diurnal species.
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Thonis A, Ceballos RM, Tuen AA, Lovegrove BG, Levesque DL. Small Tropical Mammals Can Take the Heat: High Upper Limits of Thermoneutrality in a Bornean Treeshrew. Physiol Biochem Zool 2020; 93:199-209. [PMID: 32196407 DOI: 10.1086/708467] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Tropical ectotherms are generally believed to be more vulnerable to global heating than temperate species. Currently, however, we have insufficient knowledge of the thermoregulatory physiology of equatorial tropical mammals, particularly of small diurnal mammals, to enable similar predictions. In this study, we measured the resting metabolic rates (via oxygen consumption) of wild-caught lesser treeshrews (Tupaia minor, order Scandentia) over a range of ambient temperatures. We predicted that, similar to other treeshrews, T. minor would exhibit more flexibility in body temperature regulation and a wider thermoneutral zone compared with other small mammals because these thermoregulatory traits provide both energy and water savings at high ambient temperatures. Basal metabolic rate was on average 1.03±0.10 mL O2 h-1 g-1, which is within the range predicted for a 65-g mammal. We calculated the lower critical temperature of the thermoneutral zone at 31.0°C (95% confidence interval: 29.3°-32.7°C), but using metabolic rates alone, we could not determine the upper critical temperature at ambient temperatures as high as 36°C. The thermoregulatory characteristics of lesser treeshrews provide a means of saving energy and water at temperatures well in excess of their current environmental temperatures. Our research highlights the knowledge gaps in our understanding of the energetics of mammals living in high-temperature environments, specifically in the equatorial tropics, and questions the purported lack of variance in the upper critical temperatures of the thermoneutral zone in mammals, emphasizing the importance of further research in the tropics.
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14
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Lovegrove BG. Obligatory Nocturnalism in Triassic Archaic Mammals: Preservation of Sperm Quality? Physiol Biochem Zool 2019; 92:544-553. [DOI: 10.1086/705440] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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15
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Gerson AR, McKechnie AE, Smit B, Whitfield MC, Smith EK, Talbot WA, McWhorter TJ, Wolf BO. The functional significance of facultative hyperthermia varies with body size and phylogeny in birds. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13274] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
| | - Andrew E. McKechnie
- South African Research Chair in Conservation Physiology, National Zoological Garden South African National Biodiversity Institute Pretoria South Africa
- DST‐NRF Centre of Excellence at the FitzPatrick InstituteDepartment of Zoology and Entomology University of Pretoria Hatfield South Africa
| | - Ben Smit
- DST‐NRF Centre of Excellence at the FitzPatrick InstituteDepartment of Zoology and Entomology Rhodes University Grahamstown South Africa
| | - Maxine C. Whitfield
- DST‐NRF Centre of Excellence at the FitzPatrick InstituteDepartment of Zoology and Entomology University of Pretoria Hatfield South Africa
| | - Eric K. Smith
- Department of Biology University of New Mexico Albuquerque New Mexico
| | - William A. Talbot
- Department of Biology University of New Mexico Albuquerque New Mexico
| | - Todd J. McWhorter
- School of Animal and Veterinary Sciences University of Adelaide Adelaide South Australia Australia
| | - Blair O. Wolf
- Department of Biology University of New Mexico Albuquerque New Mexico
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16
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Reher S, Ehlers J, Rabarison H, Dausmann KH. Short and hyperthermic torpor responses in the Malagasy bat Macronycteris commersoni reveal a broader hypometabolic scope in heterotherms. J Comp Physiol B 2018; 188:1015-1027. [PMID: 30121696 DOI: 10.1007/s00360-018-1171-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 06/23/2018] [Accepted: 07/05/2018] [Indexed: 11/28/2022]
Abstract
The energy budgets of animal species are closely linked to their ecology, and balancing energy expenditure with energy acquisition is key for survival. Changes in animals' environments can be challenging, particularly for bats, which are small endotherms with large uninsulated flight membranes. Heterothermy is a powerful response used to cope with changing environmental conditions. Recent research has revealed that many tropical and subtropical species are heterothermic and display torpor with patterns unlike those of "classical" heterotherms from temperate and arctic regions. However, only a handful of studies investigating torpor in bats in their natural environment exist. Therefore, we investigated whether the Malagasy bat Macronycteris commersoni enters torpor in the driest and least predictable region in Madagascar. We examined the energy balance and thermal biology of M. commersoni in the field by relating metabolic rate (MR) and skin temperature (Tskin) measurements to local environmental characteristics in the dry and rainy seasons. Macronycteris commersoni entered torpor and showed extreme variability in torpor patterns, including surprisingly short torpor bouts, lasting on average 20 min, interrupted by MR peaks. Torpid MR was remarkably low (0.13 ml O2 h-1 g-1), even when Tskin exceeded that of normothermia (41 °C). Macronycteris commersoni is thus physiologically capable of (1) entering torpor at high ambient temperature and Tskin and (2) rapidly alternating between torpid and normothermic MR resulting in very short bouts. This suggests that the scope of hypometabolism amongst heterothermic animals is broader than previously assumed and underlines the importance of further investigation into the torpor continuum.
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Affiliation(s)
- Stephanie Reher
- Functional Ecology, Institute for Zoology, University Hamburg, Martin-Luther-King-Platz 3, 20146, Hamburg, Germany.
| | - Julian Ehlers
- Animal Ecology and Conservation, Institute for Zoology, University Hamburg, Martin-Luther-King-Platz 3, 20146, Hamburg, Germany
| | - Hajatiana Rabarison
- Mention Zoologie et Biodiversité Animale, Faculté des Sciences, Université d'Antananarivo, BP 906, Antananarivo 101, Madagascar
| | - Kathrin H Dausmann
- Functional Ecology, Institute for Zoology, University Hamburg, Martin-Luther-King-Platz 3, 20146, Hamburg, Germany
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