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Geiser F. Regional Intraspecific Differences of Thermal Biology in a Marsupial Hibernator. ECOLOGICAL AND EVOLUTIONARY PHYSIOLOGY 2024; 97:180-189. [PMID: 38875137 DOI: 10.1086/730867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2024]
Abstract
AbstractDuring periods of torpor, hibernators can reduce metabolic rate (MR) and body temperature (Tb) substantially. However, to avoid physiological dysfunction at low temperatures, they defend Tb at a critical minimum, often between ~0°C and 10°C via an increase in MR. Because thermoregulation during torpor requires extra energy, individuals with lower Tb's and thus minimal MR during torpor should be selected in colder climates. Such inter- and intraspecific variations occur in some placental mammals, but for the evolutionary separate marsupials, available information is scarce. Marsupial eastern pygmy possums (Cercartetus nanus; ~22 g body mass), widely distributed along the Australian southeastern coast including subtropical to alpine areas, were used to test the hypothesis that the defended Tb of torpid individuals is related to the climate of their habitat. Possums were captured from five regions, 1,515 km apart, with midwinter (July) minimum environmental temperatures (min Tenv's) ranging from -3.9°C to 6.6°C. Captive possums in deep torpor were slowly cooled with ambient temperature (Ta), while their MR was measured to determine the minimum torpor metabolic rate (TMR), the Ta at which their MR increased for thermoregulation (min Ta), and the corresponding minimum Tb (min Tb). Partial least squares regression analysis revealed that Ta and Tenv were the strongest explanatory variables for the min Tb. The min Tb and Ta were also correlated with latitude but not elevation of the capture sites. However, the best correlations were observed between the min Tenv and the min Tb and Ta for individuals experiencing min T env > 0 ° C ; these individuals thermoconformed to min Ta's between -0.8°C and 3.7°C, and their min Tb ranged from 0.5°C to 6.0°C and was 0.5°C-2.6°C below the min Tenv at the capture site. In contrast, individuals experiencing a min Tenv of -3.9°C regulated Tb at 0.6 ° C ± 0.2 ° C or 4.5°C above the Tenv. The minimum TMR of all possums did not differ with Ta and thus did not differ among populations and was 2.6% of the basal MR. These data provide new evidence that thermal variables of marsupials are subject to regional intraspecific variation. It suggests that min Tb is a function of the min Tenv but only above 0°C, perhaps because the T b - T a differential for torpid possums in the wild, at a min Tenv of -3.9°C, remains small enough to be compensated by a small increase in MR and does not require the physiological capability for a reduction of Tb below 0°C.
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Blanco MB, Smith DL, Greene LK, Yoder AD, Ehmke EE, Lin J, Klopfer PH. Telomere dynamics during hibernation in a tropical primate. J Comp Physiol B 2024; 194:213-219. [PMID: 38466418 DOI: 10.1007/s00360-024-01541-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 01/13/2024] [Accepted: 01/23/2024] [Indexed: 03/13/2024]
Abstract
Hibernation is a widespread metabolic strategy among mammals for surviving periods of food scarcity. During hibernation, animals naturally alternate between metabolically depressed torpor bouts and energetically expensive arousals without ill effects. As a result, hibernators are promising models for investigating mechanisms that buffer against cellular stress, including telomere protection and restoration. In non-hibernators, telomeres, the protective structural ends of chromosomes, shorten with age and metabolic stress. In temperate hibernators, however, telomere shortening and elongation can occur in response to changing environmental conditions and associated metabolic state. We investigate telomere dynamics in a tropical hibernating primate, the fat-tailed dwarf lemur (Cheirogaleus medius). In captivity, these lemurs can hibernate when maintained under cold temperatures (11-15 °C) with limited food provisioning. We study telomere dynamics in eight fat-tailed dwarf lemurs at the Duke Lemur Center, USA, from samples collected before, during, and after the hibernation season and assayed via qPCR. Contrary to our predictions, we found that telomeres were maintained or even lengthened during hibernation, but shortened immediately thereafter. During hibernation, telomere lengthening was negatively correlated with time in euthermia. Although preliminary in scope, our findings suggest that there may be a preemptive, compensatory mechanism to maintain telomere integrity in dwarf lemurs during hibernation. Nevertheless, telomere shortening immediately afterward may broadly result in similar outcomes across seasons. Future studies could profitably investigate the mechanisms that offset telomere shortening within and outside of the hibernation season and whether those mechanisms are modulated by energy surplus or crises.
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Affiliation(s)
- M B Blanco
- Duke Lemur Center, Durham, NC, 27705, USA.
- Department of Biology, Duke University, Durham, NC, 27708, USA.
| | - D L Smith
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, 94143, USA
| | - L K Greene
- Duke Lemur Center, Durham, NC, 27705, USA
- Department of Biology, Duke University, Durham, NC, 27708, USA
| | - A D Yoder
- Department of Biology, Duke University, Durham, NC, 27708, USA
| | - E E Ehmke
- Duke Lemur Center, Durham, NC, 27705, USA
| | - J Lin
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, 94143, USA
| | - P H Klopfer
- Department of Biology, Duke University, Durham, NC, 27708, USA
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Monaghan P. Linking telomere dynamics to evolution, life history and environmental change: perspectives, predictions and problems. Biogerontology 2024; 25:301-311. [PMID: 38252370 PMCID: PMC10998769 DOI: 10.1007/s10522-023-10081-8] [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: 09/25/2023] [Accepted: 11/13/2023] [Indexed: 01/23/2024]
Abstract
This perspectives paper considers the value of studying telomere biology outside of a biomedical context. I provide illustrative examples of the kinds of questions that evolutionary ecologists have addressed in studies of telomere dynamics in non-model species, primarily metazoan animals, and what this can contribute to our understanding of their evolution, life histories and health. I also discuss why the predicted relationships between telomere dynamics and life history traits, based on the detailed cellular studies in humans and model organisms, are not always found in studies in other species.
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Affiliation(s)
- Pat Monaghan
- School of Biodiversity, One Health and Veterinary Medicine, Graham Kerr Building University of Glasgow, Glasgow, G12 8QQ, UK.
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