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Herrera ND, Bell KC, Callahan CM, Nordquist E, Sarver BAJ, Sullivan J, Demboski JR, Good JM. Genomic resolution of cryptic species diversity in chipmunks. Evolution 2022; 76:2004-2019. [PMID: 35778920 DOI: 10.1111/evo.14546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 06/01/2022] [Accepted: 06/06/2022] [Indexed: 01/22/2023]
Abstract
Discovery of cryptic species is essential to understand the process of speciation and assessing the impacts of anthropogenic stressors. Here, we used genomic data to test for cryptic species diversity within an ecologically well-known radiation of North American rodents, western chipmunks (Tamias). We assembled a de novo reference genome for a single species (Tamias minimus) combined with new and published targeted sequence-capture data for 21,551 autosomal and 493 X-linked loci sampled from 121 individuals spanning 22 species. We identified at least two cryptic lineages corresponding with an isolated subspecies of least chipmunk (T. minimus grisescens) and with a restricted subspecies of the yellow-pine chipmunk (Tamias amoenus cratericus) known only from around the extensive Craters of the Moon lava flow. Additional population-level sequence data revealed that the so-called Crater chipmunk is a distinct species that is abundant throughout the coniferous forests of southern Idaho. This cryptic lineage does not appear to be most closely related to the ecologically and phenotypically similar yellow-pine chipmunk but does show evidence for recurrent hybridization with this and other species.
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Affiliation(s)
- Nathanael D Herrera
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
| | - Kayce C Bell
- Natural History Museum of Los Angeles County, Los Angeles, California, USA
| | - Colin M Callahan
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
| | - Erin Nordquist
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
| | - Brice A J Sarver
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
| | - Jack Sullivan
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, USA.,Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho, Moscow, Idaho, USA
| | - John R Demboski
- Department of Zoology, Denver Museum of Nature & Sciences, Denver, Colorado, USA
| | - Jeffrey M Good
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA.,Wildlife Biology Program, University of Montana, Missoula, Montana, USA
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Abstract
ABSTRACT
Hypoxia is one of the strongest environmental drivers of cellular and physiological adaptation. Although most mammals are largely intolerant of hypoxia, some specialized species have evolved mitigative strategies to tolerate hypoxic niches. Among the most hypoxia-tolerant mammals are naked mole-rats (Heterocephalus glaber), a eusocial species of subterranean rodent native to eastern Africa. In hypoxia, naked mole-rats maintain consciousness and remain active despite a robust and rapid suppression of metabolic rate, which is mediated by numerous behavioural, physiological and cellular strategies. Conversely, hypoxia-intolerant mammals and most other hypoxia-tolerant mammals cannot achieve the same degree of metabolic savings while staying active in hypoxia and must also increase oxygen supply to tissues, and/or enter torpor. Intriguingly, recent studies suggest that naked mole-rats share many cellular strategies with non-mammalian vertebrate champions of anoxia tolerance, including the use of alternative metabolic end-products and potent pH buffering mechanisms to mitigate cellular acidification due to upregulation of anaerobic metabolic pathways, rapid mitochondrial remodelling to favour increased respiratory efficiency, and systemic shifts in energy prioritization to maintain brain function over that of other tissues. Herein, I discuss what is known regarding adaptations of naked mole-rats to a hypoxic lifestyle, and contrast strategies employed by this species to those of hypoxia-intolerant mammals, closely related African mole-rats, other well-studied hypoxia-tolerant mammals, and non-mammalian vertebrate champions of anoxia tolerance. I also discuss the neotenic theory of hypoxia tolerance – a leading theory that may explain the evolutionary origins of hypoxia tolerance in mammals – and highlight promising but underexplored avenues of hypoxia-related research in this fascinating model organism.
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Affiliation(s)
- Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 9A7. University of Ottawa, Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada, K1H 8M5
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Cheng H, Sebaa R, Malholtra N, Lacoste B, El Hankouri Z, Kirby A, Bennett NC, van Jaarsveld B, Hart DW, Tattersall GJ, Harper ME, Pamenter ME. Naked mole-rat brown fat thermogenesis is diminished during hypoxia through a rapid decrease in UCP1. Nat Commun 2021; 12:6801. [PMID: 34815412 PMCID: PMC8610999 DOI: 10.1038/s41467-021-27170-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 11/08/2021] [Indexed: 11/17/2022] Open
Abstract
Naked mole-rats are among the most hypoxia-tolerant mammals. During hypoxia, their body temperature (Tb) decreases via unknown mechanisms to conserve energy. In small mammals, non-shivering thermogenesis in brown adipose tissue (BAT) is critical to Tb regulation; therefore, we hypothesize that hypoxia decreases naked mole-rat BAT thermogenesis. To test this, we measure changes in Tb during normoxia and hypoxia (7% O2; 1-3 h). We report that interscapular thermogenesis is high in normoxia but ceases during hypoxia, and Tb decreases. Furthermore, in BAT from animals treated in hypoxia, UCP1 and mitochondrial complexes I-V protein expression rapidly decrease, while mitochondria undergo fission, and apoptosis and mitophagy are inhibited. Finally, UCP1 expression decreases in hypoxia in three other social African mole-rat species, but not a solitary species. These findings suggest that the ability to rapidly down-regulate thermogenesis to conserve oxygen in hypoxia may have evolved preferentially in social species.
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Affiliation(s)
- Hang Cheng
- grid.28046.380000 0001 2182 2255Department of Biology, University of Ottawa, Ottawa, ON Canada
| | - Rajaa Sebaa
- grid.28046.380000 0001 2182 2255Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON Canada ,grid.28046.380000 0001 2182 2255Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON Canada ,grid.449644.f0000 0004 0441 5692Department of Medical Laboratories, College of Applied Medical Sciences, University of Shaqra, Duwadimi, Saudi Arabia
| | - Nikita Malholtra
- grid.28046.380000 0001 2182 2255Department of Biology, University of Ottawa, Ottawa, ON Canada
| | - Baptiste Lacoste
- grid.28046.380000 0001 2182 2255Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON Canada ,grid.28046.380000 0001 2182 2255University of Ottawa Brain and Mind Research Institute, Ottawa, ON Canada ,grid.412687.e0000 0000 9606 5108Neuroscience Program, Ottawa Hospital Research Institute, Ottawa, ON Canada
| | - Ziyad El Hankouri
- grid.28046.380000 0001 2182 2255Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON Canada ,grid.28046.380000 0001 2182 2255Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON Canada
| | - Alexia Kirby
- grid.28046.380000 0001 2182 2255Department of Biology, University of Ottawa, Ottawa, ON Canada
| | - Nigel C. Bennett
- grid.49697.350000 0001 2107 2298Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Barry van Jaarsveld
- grid.49697.350000 0001 2107 2298Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Daniel W. Hart
- grid.49697.350000 0001 2107 2298Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Glenn J. Tattersall
- grid.411793.90000 0004 1936 9318Department of Biological Sciences, Brock University, St. Catharines, ON Canada
| | - Mary-Ellen Harper
- Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada. .,Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON, Canada.
| | - Matthew E. Pamenter
- grid.28046.380000 0001 2182 2255Department of Biology, University of Ottawa, Ottawa, ON Canada ,grid.28046.380000 0001 2182 2255University of Ottawa Brain and Mind Research Institute, Ottawa, ON Canada
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Kirby AM, Fairman GD, Pamenter ME. Atypical behavioural, metabolic and thermoregulatory responses to hypoxia in the naked mole rat (Heterocephalus glaber
). J Zool (1987) 2018. [DOI: 10.1111/jzo.12542] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Alexia M Kirby
- Department of Biology; University of Ottawa; Ottawa ON Canada
| | | | - Matthew E Pamenter
- Department of Biology; University of Ottawa; Ottawa ON Canada
- Brain and Mind Research Institute; University of Ottawa; Ottawa ON Canada
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Nathaniel TI, Soyinka JO, Adedeji A, Imeh-Nathaniel A. Molecular and Physiological Factors of Neuroprotection in Hypoxia-tolerant Models: Pharmacological Clues for the Treatment of Stroke. J Exp Neurosci 2015; 9:1-5. [PMID: 25780340 PMCID: PMC4346302 DOI: 10.4137/jen.s22512] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 01/11/2015] [Accepted: 01/13/2015] [Indexed: 11/05/2022] Open
Abstract
The naked mole-rat possesses several unique physiological and molecular features that underlie their remarkably and exceptional resistance to tissue hypoxia. Elevated pattern of Epo, an erythropoietin (Epo) factor; c-fos; vascular endothelial growth factor (VEGF); and hypoxia-inducible factors (HIF-1α) contribute to the adaptive strategy to cope with hypoxic stress. Moreover, the naked mole-rat has a lower metabolic rate than any other eutherian mammal of comparable size that has been studied. The ability to actively reduce metabolic rate represents a strategy widely used in the face of decreased tissue oxygen availability. Understanding the different molecular and physiological factors that induce metabolic suppression could guide the development of pharmacological agents for the clinical management of stroke patient.
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Affiliation(s)
- Thomas I Nathaniel
- University of South Carolina School of Medicine—Greenville, Greenville, SC, USA
| | - Julius O Soyinka
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Nigeria
| | - Adekunle Adedeji
- Department of Health Science, Eastern Tennessee State University, Johnson City, TN, USA
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Tattersall GJ, Sinclair BJ, Withers PC, Fields PA, Seebacher F, Cooper CE, Maloney SK. Coping with Thermal Challenges: Physiological Adaptations to Environmental Temperatures. Compr Physiol 2012; 2:2151-202. [DOI: 10.1002/cphy.c110055] [Citation(s) in RCA: 184] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Careau V, Garant D, Humphries M. Free-ranging eastern chipmunks (Tamias striatus) infected with bot fly (Cuterebra emasculator) larvae have higher resting but lower maximum metabolism. CAN J ZOOL 2012. [DOI: 10.1139/z2012-008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Given the ubiquity and evolutionary importance of parasites, their effect on the energy budget of mammals remains surprisingly unclear. The eastern chipmunk ( Tamias striatus (L., 1758)) is a burrowing rodent that is commonly infected by cuterebrid bot fly ( Cuterebra emasculator Fitch, 1856) larvae. We measured resting metabolic rate (RMR) and cold-induced Vo2-max (under heliox atmosphere) in 20 free-ranging individuals, of which 4 individuals were infected by one or two larva. We found that RMR was significantly higher in chipmunks infected by bot fly larvae (mean ± SE = 0.88 ± 0.05 W) than in uninfected individuals (0.74 ± 0.02 W). In contrast, Vo2-max was significantly lower in chipmunks infected by bot fly larvae (4.96 ± 0.70 W) than in uninfected individuals (6.37 ± 0.16 W). Consequently, the aerobic scope (ratio of Vo2-max to RMR) was negatively correlated with the number of bot fly larvae (infected individuals = 5.74 ± 1.03 W; noninfected individuals = 8.67 ± 0.26 W). Finally, after accounting for the effects of body mass and bot fly parasitism on RMR and Vo2-max, there was no correlation between the two variables among individuals within our population. In addition to providing the first estimate of Vo2-max in T. striatus, these results offer additional evidence that bot fly parasitism has significant impacts on the metabolic ecology of this host species.
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Affiliation(s)
- V. Careau
- Département de Biologie, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada
| | - D. Garant
- Département de Biologie, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada
| | - M.M. Humphries
- Natural Resource Sciences, McGill University, Macdonald Campus, QC H9X 3V9, Canada
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Tattersall GJ, Milsom WK. Hypoxia reduces the hypothalamic thermogenic threshold and thermosensitivity. J Physiol 2009; 587:5259-74. [PMID: 19770191 PMCID: PMC2790263 DOI: 10.1113/jphysiol.2009.175828] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2009] [Accepted: 09/14/2009] [Indexed: 12/13/2022] Open
Abstract
Hypoxia is well known to reduce the body temperature (T(b)) of mammals, although the neural origins of this response remain uncertain. Short-term hypoxic exposure causes a reduction in the lower critical temperature of the thermal neutral zone and a reduction in whole body thermal conductance of rodents, providing indirect support that hypoxia lowers T(b) in a regulated manner. In this study, we examined directly the potential for changes in central thermosensitivity to evoke the hypoxic metabolic response by heating and cooling the preoptic area of the hypothalamus (the area which integrates thermoreceptor input and regulates thermoeffector outputs) using chronic, indwelling thermodes in ground squirrels during normoxia and hypoxia (7, 10 and 12% O(2)). We found that the threshold hypothalamic temperature for the metabolic response to cooling (T(th)) of approximately 38 degrees C in normoxia was proportionately reduced in hypoxia (down to 28-31 degrees C at 7% O(2)) and that the metabolic thermosensitivity (alpha; the change in metabolic rate for any given change in hypothalamic temperature below the lower critical temperature) was comparatively reduced by 5 to 9 times. This provides strong support for the hypothesis that the fall in temperature that occurs during hypoxia is the result of a reduction in the activation of thermogenic mechanisms. The decrease in the central thermosensitivity in hypoxia, however, appears to be a critical factor in the alteration of mammalian T(b). We suggest, therefore, that an altered central thermosensitivity may provide a proximate explanation of how low oxygen and similar stressors reduce normal fluctuations in T(b) (i.e. circadian), in addition to the depression in regulated T(b).
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Affiliation(s)
- Glenn J Tattersall
- Department of Biological Sciences, Brock University, St Catharines, ON, Canada L2S 3A1.
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Levesque DL, Tattersall GJ. Seasonal torpor and normothermic energy metabolism in the Eastern chipmunk (Tamias striatus). J Comp Physiol B 2009; 180:279-92. [PMID: 19756651 DOI: 10.1007/s00360-009-0405-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2009] [Revised: 08/05/2009] [Accepted: 08/18/2009] [Indexed: 10/20/2022]
Abstract
To assess the changes in thermoregulatory characteristics that accompany the seasonal expression of torpor we measured seasonal differences in body mass adjustments, body temperature (T (b)) and metabolic rate (MR) in both summer- and winter-acclimated individuals from a species of food-storing hibernator, the Eastern chipmunk (Tamias striatus). Torpor occurred only in the winter and was associated with lower normothermic T (b), during inter-bout arousal periods than in the summer. Chipmunks increased body mass before the initiation of torpor in winter, and steadily lost mass as the hibernation season progressed. Torpor expression was correlated to initial mass gain, with the individuals who showed the largest mass increase in the fall showing the highest degree of torpor. Acclimation to winter-like conditions produced a decline in normothermic MR at all ambient temperatures examined. The findings indicate that torpor expression is accompanied by a decrease in T (b) and MR during normothermy, indicating that a conservation of energy metabolism occurs, not only in torpor, but also during the inter-bout arousal periods.
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Affiliation(s)
- Danielle L Levesque
- Department of Biological Sciences, Brock University, St Catharines, ON, L2S 3A1, Canada.
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