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Gerhardt P, Begall S, Frädrich C, Renko K, Heinrich A, Köhrle J, Henning Y. Low thyroxine serves as an upstream regulator of ecophysiological adaptations in Ansell's mole-rats. Front Endocrinol (Lausanne) 2024; 15:1329083. [PMID: 38567302 PMCID: PMC10985354 DOI: 10.3389/fendo.2024.1329083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 03/04/2024] [Indexed: 04/04/2024] Open
Abstract
Introduction About 10% of all rodent species have evolved a subterranean way of life, although life in subterranean burrows is associated with harsh environmental conditions that would be lethal to most animals living above ground. Two key adaptations for survival in subterranean habitats are low resting metabolic rate (RMR) and core body temperature (Tb). However, the upstream regulation of these traits was unknown thus far. Previously, we have reported exceptionally low concentrations of the thyroid hormone (TH) thyroxine (T4), and peculiarities in TH regulating mechanisms in two African mole-rat species, the naked mole-rat and the Ansell's mole-rat. Methods In the present study, we treated Ansell's mole-rats with T4 for four weeks and analyzed treatment effects on the tissue and whole organism level with focus on metabolism and thermoregulation. Results We found RMR to be upregulated by T4 treatment but not to the extent that was expected based on serum T4 concentrations. Our data point towards an extraordinary capability of Ansell's mole-rats to effectively downregulate TH signaling at tissue level despite very high serum TH concentrations, which most likely explains the observed effects on RMR. On the other hand, body weight was decreased in T4-treated animals and Tb was upregulated by T4 treatment. Moreover, we found indications of the hypothalamus-pituitary-adrenal axis potentially influencing the treatment effects. Conclusion Taken together, we provide the first experimental evidence that the low serum T4 concentrations of Ansell's mole-rats serve as an upstream regulator of low RMR and Tb. Thus, our study contributes to a better understanding of the ecophysiological evolution of the subterranean lifestyle in African mole-rats.
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Affiliation(s)
- Patricia Gerhardt
- Institute of Physiology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Sabine Begall
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
| | - Caroline Frädrich
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institut für Experimentelle Endokrinologie, Berlin, Germany
| | - Kostja Renko
- German Federal Institute for Risk Assessment, German Centre for the Protection of Laboratory Animals (Bf3R), Berlin, Germany
| | - Alexandra Heinrich
- Institute of Physiology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Josef Köhrle
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institut für Experimentelle Endokrinologie, Berlin, Germany
| | - Yoshiyuki Henning
- Institute of Physiology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
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Henning Y, Adam K, Gerhardt P, Begall S. Hypoxic and hypercapnic burrow conditions lead to downregulation of free triiodothyronine and hematocrit in Ansell's mole-rats (Fukomys anselli). J Comp Physiol B 2024; 194:33-40. [PMID: 38059996 PMCID: PMC10940439 DOI: 10.1007/s00360-023-01526-0] [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: 09/04/2023] [Revised: 11/01/2023] [Accepted: 11/08/2023] [Indexed: 12/08/2023]
Abstract
African mole-rats live in self-dug burrow systems under hypoxic and hypercapnic conditions. Adaptations to hypoxia include suppression of resting metabolic rate (RMR) and core body temperature (Tb). Because the thyroid hormones (THs) thyroxine (T4) and triiodothyronine (T3) are positive regulators of RMR and Tb, we hypothesized that serum TH concentrations would also be downregulated under hypoxic conditions. To test this hypothesis, we kept Ansell's mole-rats (Fukomys anselli) in terraria filled with soil in which they were allowed to construct underground burrows to achieve chronic intermittent hypoxia and hypercapnia. The animals stayed in these hypoxic and hypercapnic burrows voluntarily, although given the choice to stay aboveground. We collected blood samples before and after treatment to measure serum T4 and T3 concentrations as well as hematological parameters. The free fraction of the transcriptionally-active T3 was significantly decreased after treatment, indicating that cellular TH signaling was downregulated via peripheral mechanisms, consistent with the assumption that aerobic metabolism is downregulated under hypoxic conditions. Furthermore, we found that hematocrit and hemoglobin concentrations were also downregulated after treatment, suggesting that oxygen demand decreases under hypoxia, presumably due to the metabolic shift towards anaerobic metabolism. Taken together, we have identified a potential upstream regulator of physiological adaptations to hypoxia in these highly hypoxia-tolerant animals.
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Affiliation(s)
- Yoshiyuki Henning
- Institute of Physiology, University Hospital Essen, University of Duisburg-Essen, Hufelandstr. 55, 45147, Essen, Germany.
| | - Kamilla Adam
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
| | - Patricia Gerhardt
- Institute of Physiology, University Hospital Essen, University of Duisburg-Essen, Hufelandstr. 55, 45147, Essen, Germany
| | - Sabine Begall
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
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Courcelle M, Fabre PH, Douzery EJP. Phylogeny, Ecology, and Gene Families Covariation Shaped the Olfactory Subgenome of Rodents. Genome Biol Evol 2023; 15:evad197. [PMID: 37972291 PMCID: PMC10653590 DOI: 10.1093/gbe/evad197] [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] [Accepted: 10/29/2023] [Indexed: 11/19/2023] Open
Abstract
Olfactory receptor (OR) genes represent the largest multigenic family in mammalian genomes and encode proteins that bind environmental odorant molecules. The OR repertoire is extremely variable among species and is subject to many gene duplications and losses, which have been linked to ecological adaptations in mammals. Although they have been studied on a broad taxonomic scale (i.e., placental), finer sampling has rarely been explored in order to better capture the mechanisms that drove the evolution of the OR repertoire. Among placental mammals, rodents are well-suited for this task, as they exhibit diverse life history traits, and genomic data are available for most major families and a diverse array of lifestyles. In this study, 53 rodent published genomes were mined for their OR subgenomes. We retrieved more than 85,000 functional and pseudogene OR sequences that were subsequently classified into phylogenetic clusters. Copy number variation among rodents is similar to that of other mammals. Using our OR counts along with comparative phylogenetic approaches, we demonstrated that ecological niches such as diet, period of activity, and a fossorial lifestyle strongly impacted the proportion of OR pseudogenes. Within the OR subgenome, phylogenetic inertia was the main factor explaining the relative variations of the 13 OR gene families. However, a striking exception was a convergent 10-fold expansion of the OR family 14 among the phylogenetically divergent subterranean mole-rat lineages belonging to Bathyergidae and Spalacidae families. This study illustrates how the diversity of the OR repertoire has evolved among rodents, both shaped by selective forces stemming from species life history traits and neutral evolution along the rodent phylogeny.
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Affiliation(s)
- Maxime Courcelle
- Institutdes Sciences de l’Evolution de Montpellier (ISEM), CNRS, IRD, EPHE, Université de Montpellier, Montpellier, France
- CIRAD, UMR ASTRE, Montpellier, France
| | - Pierre-Henri Fabre
- Institutdes Sciences de l’Evolution de Montpellier (ISEM), CNRS, IRD, EPHE, Université de Montpellier, Montpellier, France
- Mammal Section, Life Sciences, Vertebrate Division, The Natural History Museum, London, United Kingdom
- Institut Universitaire de France (IUF), Section Biologie-Médecine-Santé, Paris, France
| | - Emmanuel J P Douzery
- Institutdes Sciences de l’Evolution de Montpellier (ISEM), CNRS, IRD, EPHE, Université de Montpellier, Montpellier, France
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Šumbera R, Lövy M, Nevo E, Okrouhlík J. Thermal biology in the Upper Galili Mountain blind mole rat (Nannospalax galili) and an overview of spalacine energetics. J Therm Biol 2023; 115:103618. [PMID: 37399744 DOI: 10.1016/j.jtherbio.2023.103618] [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: 02/17/2023] [Revised: 05/26/2023] [Accepted: 06/09/2023] [Indexed: 07/05/2023]
Abstract
Several hundred mammalian species thrive in complex burrow systems, which protect them from climatic extremes and predation. At the same time, it is also a stressful environment due to low food supply, high humidity, and, in some cases, a hypoxic and hypercapnic atmosphere. To face such conditions, subterranean rodents have convergently evolved low basal metabolic rate, high minimal thermal conductance and low body temperature. Although these parameters have been intensively studied in the last decades, such information is far from being well-known in one of the most studied groups of subterranean rodents, the blind mole rats of the genus Nannospalax. The lack of information is particularly noticeable for parameters such as the upper critical temperature and the width of the thermoneutral zone. In our study, we analysed the energetics of the Upper Galilee Mountain blind mole rat Nannospalax galili and found its basal metabolic rate of 0.84 ± 0.10 mL O2×g-1 × h-1, thermoneutral zone between 28 and 35 °C, mean Tb within the zone of 36.3 ± 0.6 °C, and minimal thermal conductance equal to 0.082 mL O2×g-1 × h-1 × C-1. Nannospalax galili is a truly homeothermic rodent well adapted to face lower ambient temperatures, because its Tb was stable down to the lowest temperature measured (10 °C). At the same time, a relatively high basal metabolic rate and relatively low minimal thermal conductance for a subterranean rodent of such body mass, and the difficulty of surviving ambient temperatures slightly above upper critical temperature, indicates problems with sufficient heat dissipation at higher temperatures. This can easily lead to overheating, that is relevant mainly during the hot-dry season. These findings suggest that N. galili can be threatened by ongoing global climate change.
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Affiliation(s)
- Radim Šumbera
- Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czech Republic.
| | - Matěj Lövy
- Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czech Republic
| | - Eviatar Nevo
- Institute of Evolution, University of Haifa, 3498838, Haifa, Israel
| | - Jan Okrouhlík
- Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czech Republic
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Šumbera R, Uhrová M, Begall S, Caspar KR, Jerkovičová D, Van Daele P, Chitaukali WN, Faulkes CG, Bennett NC, Johannes C, Burda H, Mikula O. The biology of an isolated Mashona mole-rat population from southern Malawi, with implications for the diversity and biogeography of the genus Fukomys. ORG DIVERS EVOL 2023. [DOI: 10.1007/s13127-023-00604-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
AbstractThe Mashona mole-rat, Fukomys darlingi (Thomas, 1895), is a little studied social African mole-rat (Bathyergidae) from south-astern Africa. Here, we present an integrative study characterizing the genetic diversity of populations assigned to F. darlingi with special focus on animals from Nsanje, southern Malawi. These mole-rats show pronounced differences in body mass and general appearance compared to nominate F. darlingi from Zimbabwe and Mozambique, but their taxonomic status has so far remained unclear. A genetic analysis encompassing all major lineages of the genus Fukomys suggests that this population indeed represents a deeply nested lineage within the F. darlingi clade. The karyotype of the Nsanje mole-rats also corresponds to that of the nominate form, being 2n = 54. While both nuclear and mitochondrial data agree about the assignment of the Nsanje mole-rats to F. darlingi, our analyses revealed substantial mitonuclear discordance for other branches within the Fukomys phylogenetic tree. Nsanje mole-rats are significantly larger than nominate F. darlingi and their ontogeny and reproduction closely resemble similar-sized congeneric species rather than the nominate population. The somatic growth of the Nsanje form is the slowest of all African mole-rats. The maximum life span of F. darlingi is at least 19 years. The observed differences between nominate F. darlingi and mole-rats from Nsanje may be attributed mainly to their different body mass. Our study highlights the advantages of an integrative approach for understanding the diversity of African mole-rats and emphasizes the great intraspecific variability that may be encountered in these underground-dwelling rodents.
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Comparative analysis of thyroid hormone systems in rodents with subterranean lifestyle. Sci Rep 2023; 13:3122. [PMID: 36813840 PMCID: PMC9946999 DOI: 10.1038/s41598-023-30179-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 02/17/2023] [Indexed: 02/24/2023] Open
Abstract
African mole-rats are subterranean rodents inhabiting underground burrows. This habitat entails risks of overheating, hypoxia, and scarce food availability. Consequently, many subterranean species have evolved low basal metabolism and low body temperature, but the regulation of these traits at the molecular level were unknown. Measurements of serum thyroid hormone (TH) concentrations in African mole-rats have revealed a unique TH phenotype, which deviates from the typical mammalian pattern. Since THs are major regulators of metabolic rate and body temperature, we further characterised the TH system of two African mole-rat species, the naked mole-rat (Heterocephalus glaber) and the Ansell's mole-rat (Fukomys anselli) at the molecular level in a comparative approach involving the house mouse (Mus musculus) as a well-studied laboratory model in TH research. Most intriguingly, both mole-rat species had low iodide levels in the thyroid and naked mole-rats showed signs of thyroid gland hyperplasia. However, contrary to expectations, we found several species-specific differences in the TH systems of both mole-rat species, although ultimately resulting in similar serum TH concentrations. These findings indicate a possible convergent adaptation. Thus, our study adds to our knowledge for understanding adaptations to the subterranean habitat.
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Luna F, Okrouhlík J, McKechnie AE, Bennett NC, Šumbera R. Non‐shivering thermogenesis in four species of African mole‐rats differing in their sociality. J Zool (1987) 2021. [DOI: 10.1111/jzo.12892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- F. Luna
- Laboratorio de Ecología Fisiológica y del Comportamiento Instituto de Investigaciones Marinas y Costeras (IIMyC) CONICET‐UNMdP Mar del Plata Argentina
| | - J. Okrouhlík
- Department of Zoology Faculty of Science University of South Bohemia České Budějovice Czech Republic
- Department of Zoology and Entomology Mammal Research Institute University of Pretoria Pretoria South Africa
| | - A. E. McKechnie
- Department of Zoology and Entomology Mammal Research Institute University of Pretoria Pretoria South Africa
- South African Research Chair in Conservation Physiology South African National Biodiversity Institute Pretoria South Africa
| | - N. C. Bennett
- Department of Zoology and Entomology Mammal Research Institute University of Pretoria Pretoria South Africa
| | - R. Šumbera
- Department of Zoology Faculty of Science University of South Bohemia České Budějovice Czech Republic
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The Idiosyncratic Physiological Traits of the Naked Mole-Rat; a Resilient Animal Model of Aging, Longevity, and Healthspan. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1319:221-254. [PMID: 34424518 DOI: 10.1007/978-3-030-65943-1_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The subterranean-dwelling naked mole-rat (Heterocephalus glaber) is an extremophilic rodent, able to thrive in the harsh underground conditions of sub-Saharan Northeast Africa. This pelage-free mammal exhibits numerous unusual ecophysiological features including pronounced tolerance of thermolability, hypoxia, hypercapnia and noxious substances. As a mammal, the naked mole-rat provides a proof-of-concept that age-related changes in physiology are avoidable. At ages far beyond their expected lifespans given both their body size and/or the timing of early developmental milestones, naked mole-rats fail to exhibit meaningful changes in physiological health or demographic mortality. Lack of physiological deterioration with age is also evident in lean and fat mass, bone quality, and reproductive capacity. Rather, regardless of age, under basal conditions naked mole-rats appear to "idle on low" with their "shields up" as is manifested by low body temperature, metabolic rate, cardiac output and kidney concentrating ability, enabling better protection of organs and cellular function. When needed, they can nevertheless ramp up these functions, increasing cardiac output and metabolism 2-5 fold. Here we review many unusual aspects of their physiology and examine how these attributes facilitate both tolerance of the diverse suite of hostile conditions encountered in their natural milieu as well as contribute to their extraordinary longevity and resistance to common, age-related chronic diseases.
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Montoya‐Sanhueza G, Bennett NC, Oosthuizen MK, Dengler‐Crish CM, Chinsamy A. Bone remodeling in the longest living rodent, the naked mole-rat: Interelement variation and the effects of reproduction. J Anat 2021; 239:81-100. [PMID: 33554344 PMCID: PMC8197955 DOI: 10.1111/joa.13404] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 01/09/2021] [Accepted: 01/14/2021] [Indexed: 12/14/2022] Open
Abstract
The pattern of bone remodeling of one of the most peculiar mammals in the world, the naked mole-rat (NMR), was assessed. NMRs are known for their long lifespans among rodents and for having low metabolic rates. We assessed long-term in vivo bone labeling of subordinate individuals, as well as the patterns of bone resorption and bone remodeling in a large sample including reproductive and non-reproductive individuals (n = 70). Over 268 undecalcified thin cross-sections from the midshaft of humerus, ulna, femur and tibia were analyzed with confocal fluorescence and polarized light microscopy. Fluorochrome analysis revealed low osteogenesis, scarce bone resorption and infrequent formation of secondary osteons (Haversian systems) (i.e., slow bone turnover), thus most likely reflecting the low metabolic rates of this species. Secondary osteons occurred regardless of reproductive status. However, considerable differences in the degree of bone remodeling were found between breeders and non-breeders. Pre-reproductive stages (subordinates) exhibited quite stable skeletal homeostasis and bone structure, although the attainment of sexual maturity and beginning of reproductive cycles in female breeders triggered a series of anabolic and catabolic processes that up-regulate bone turnover, most likely associated with the increased metabolic rates of reproduction. Furthermore, bone remodeling was more frequently found in stylopodial elements compared to zeugopodial elements. Despite the limited bone remodeling observed in NMRs, the variation in the pattern of skeletal homeostasis (interelement variation) reported here represents an important aspect to understand the skeletal dynamics of a small mammal with low metabolic rates. Given the relevance of the remodeling process among mammals, this study also permitted the comparison of such process with the well-documented histomorphology of extinct therapsids (i.e., mammalian precursors), thus evidencing that bone remodeling and its endocortical compartmentalization represent ancestral features among the lineage that gave rise to mammals. It is concluded that other factors associated with development (and not uniquely related to biomechanical loading) can also have an important role in the development of bone remodeling.
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Affiliation(s)
- Germán Montoya‐Sanhueza
- Department of Biological SciencesUniversity of Cape TownCape TownSouth Africa
- Department of ZoologyFaculty of ScienceUniversity of South BohemiaČeské BudějoviceCzech Republic
| | - Nigel C. Bennett
- Department of Zoology and EntomologyMammal Research InstituteUniversity of PretoriaPretoriaSouth Africa
| | - Maria K. Oosthuizen
- Department of Zoology and EntomologyMammal Research InstituteUniversity of PretoriaPretoriaSouth Africa
| | | | - Anusuya Chinsamy
- Department of Biological SciencesUniversity of Cape TownCape TownSouth Africa
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Okrouhlík J, Šumbera R, Gardner B, Schoemann K, Lövy M, Bennett NC. Are southern African solitary mole-rats homeothermic or heterothermic under natural field conditions? J Therm Biol 2020; 95:102810. [PMID: 33454040 DOI: 10.1016/j.jtherbio.2020.102810] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 12/08/2020] [Accepted: 12/12/2020] [Indexed: 10/22/2022]
Abstract
Abandoning of a stable body temperature (Tb), a phenomenon known as heterothermy, is an adaptation to cope mainly with a lack of food and water, especially in species inhabiting daily or seasonally variable environments. There is increasing evidence that African mammals avoid adverse conditions by heterothermy and eventually by entering torpor. Members of subterranean rodent family, the African mole-rats (Bathyergidae), are suitable candidates to study both phenomena, because of the diversity of their strategies in respect of maintaining stable Tb ranging from homeothermic species to a mammal with the most labile Tb, the naked mole-rat. Currently, there are field data on daily and seasonal Tb in one social species only and such information are lacking for any solitary mole-rat. In our study, we recorded yearly Tb in two solitary bathyergids, the Cape mole-rat Georychus capensis and the Cape dune mole-rat Bathyergus suillus from South Africa using intraperitoneally implanted dataloggers. Since this region is characterised by changing ecological characteristics, we expected either decreases of Tb within 24 h indicating daily torpor and/or longer-term decreases of Tb, which would indicate multiday torpor. Although we found seasonally phase shifted low amplitude daily Tb cycles, we did not find any remarkable and regular daily and/or seasonal Tb deviations, likely showing an absence of torpor in both species. Due to absence of this energy saving mechanism, we may speculate that both species could be vulnerable to ongoing global climatic change.
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Affiliation(s)
- Jan Okrouhlík
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa; Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czech Republic
| | - Radim Šumbera
- Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czech Republic.
| | - Brett Gardner
- Werribee Open Range Zoo, Veterinary Hospital, Zoos Victoria, K Road, Werribee, Victoria, 3029, Australia
| | - Keegan Schoemann
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Matěj Lövy
- Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czech Republic
| | - Nigel Charles Bennett
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
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Montoya-Sanhueza G, Bennett NC, Oosthuizen MK, Dengler-Crish CM, Chinsamy A. Long bone histomorphogenesis of the naked mole-rat: Histodiversity and intraspecific variation. J Anat 2020; 238:1259-1283. [PMID: 33305850 DOI: 10.1111/joa.13381] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 11/22/2020] [Accepted: 11/23/2020] [Indexed: 02/07/2023] Open
Abstract
Lacking fur, living in eusocial colonies and having the longest lifespan of any rodent, makes naked mole-rats (NMRs) rather peculiar mammals. Although they exhibit a high degree of polymorphism, skeletal plasticity and are considered a novel model to assess the effects of delayed puberty on the skeletal system, scarce information on their morphogenesis exists. Here, we examined a large ontogenetic sample (n = 76) of subordinate individuals to assess the pattern of bone growth and bone microstructure of fore- and hindlimb bones by using histomorphological techniques. Over 290 undecalcified thin cross-sections from the midshaft of the humerus, ulna, femur, and tibia from pups, juveniles and adults were analyzed with polarized light microscopy. Similar to other fossorial mammals, NMRs exhibited a systematic cortical thickening of their long bones, which clearly indicates a conserved functional adaptation to withstand the mechanical strains imposed during digging, regardless of their chisel-tooth predominance. We describe a high histodiversity of bone matrices and the formation of secondary osteons in NMRs. The bones of pups are extremely thin-walled and grow by periosteal bone formation coupled with considerable expansion of the medullary cavity, a process probably tightly regulated and adapted to optimize the amount of minerals destined for skeletal development, to thus allow the female breeder to produce a higher number of pups, as well as several litters. Subsequent cortical thickening in juveniles involves high amounts of endosteal bone apposition, which contrasts with the bone modeling of other mammals where a periosteal predominance exists. Adults have bone matrices predominantly consisting of parallel-fibered bone and lamellar bone, which indicate intermediate to slow rates of osteogenesis, as well as the development of poorly vascularized lamellar-zonal tissues separated by lines of arrested growth (LAGs) and annuli. These features reflect the low metabolism, low body temperature and slow growth rates reported for this species, as well as indicate a cyclical pattern of osteogenesis. The presence of LAGs in captive individuals was striking and indicates that postnatal osteogenesis and its consequent cortical stratification most likely represents a plesiomorphic thermometabolic strategy among endotherms which has been suggested to be regulated by endogenous rhythms. However, the generalized presence of LAGs in this and other subterranean taxa in the wild, as well as recent investigations on variability of environmental conditions in burrow systems, supports the hypothesis that underground environments experience seasonal fluctuations that may influence the postnatal osteogenesis of animals by limiting the extension of burrow systems during the unfavorable dry seasons and therefore the finding of food resources. Additionally, the intraspecific variation found in the formation of bone tissue matrices and vascularization suggested a high degree of developmental plasticity in NMRs, which may help explaining the polymorphism reported for this species. The results obtained here represent a valuable contribution to understanding the relationship of several aspects involved in the morphogenesis of the skeletal system of a mammal with extraordinary adaptations.
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Affiliation(s)
- Germán Montoya-Sanhueza
- Department of Biological Sciences, University of Cape Town, Cape Town, South Africa.,Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Nigel C Bennett
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Maria K Oosthuizen
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | | | - Anusuya Chinsamy
- Department of Biological Sciences, University of Cape Town, Cape Town, South Africa
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Braude S, Holtze S, Begall S, Brenmoehl J, Burda H, Dammann P, Marmol D, Gorshkova E, Henning Y, Hoeflich A, Höhn A, Jung T, Hamo D, Sahm A, Shebzukhov Y, Šumbera R, Miwa S, Vyssokikh MY, Zglinicki T, Averina O, Hildebrandt TB. Surprisingly long survival of premature conclusions about naked mole‐rat biology. Biol Rev Camb Philos Soc 2020; 96:376-393. [DOI: 10.1111/brv.12660] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 10/06/2020] [Accepted: 10/13/2020] [Indexed: 12/11/2022]
Affiliation(s)
- Stan Braude
- Biology Department Washington University, One Brookings Drive St. Louis MO 63130 U.S.A
| | - Susanne Holtze
- Department of Reproduction Management Leibniz‐Institute for Zoo and Wildlife Research Berlin 10315 Germany
| | - Sabine Begall
- Department of General Zoology, Faculty of Biology University of Duisburg‐Essen, Universitätsstr Essen 45147 Germany
| | - Julia Brenmoehl
- Institute for Genome Biology Leibniz‐Institute for Farm Animal Biology Dummerstorf 18196 Germany
| | - Hynek Burda
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences Czech University of Life Sciences Praha 16500 Czech Republic
| | - Philip Dammann
- Department of General Zoology, Faculty of Biology University of Duisburg‐Essen, Universitätsstr Essen 45147 Germany
- University Hospital Essen Hufelandstr Essen 45141 Germany
| | - Delphine Marmol
- Molecular Physiology Research Unit (URPhyM), NARILIS University of Namur Namur 5000 Belgium
| | - Ekaterina Gorshkova
- Engelhardt Institute of Molecular Biology Russian Academy of Sciences, Vavilova str. 32 Moscow 119991 Russia
- Faculty of Biology Lomonosov Moscow State University Moscow 119991 Russia
| | - Yoshiyuki Henning
- University Hospital Essen Hufelandstr Essen 45141 Germany
- Institute of Physiology Department of General Zoology University of Duisburg Essen Germany
| | - Andreas Hoeflich
- Division Signal Transduction Institute for Genome Biology, Leibniz‐Institute for Farm Animal Biology, FBN Dummerstorf, Wilhelm‐Stahl‐Allee 2 Dummerstorf 18196 Germany
| | - Annika Höhn
- Department of Molecular Toxicology German Institute of Human Nutrition (DIfE) Potsdam‐Rehbrücke Nuthetal 14558 Germany
- German Center for Diabetes Research (DZD) München‐Neuherberg 85764 Germany
| | - Tobias Jung
- Department of Molecular Toxicology German Institute of Human Nutrition (DIfE) Potsdam‐Rehbrücke Nuthetal 14558 Germany
| | - Dania Hamo
- Charité ‐ Universitätsmedizin Berlin Berlin Institute of Health Center for Regenerative Therapies (BCRT) Berlin 13353 Germany
- German Rheumatism Research Centre Berlin (DRFZ) Berlin 10117 Germany
| | - Arne Sahm
- Computational Biology Group Leibniz Institute on Aging – Fritz Lipmann Institute Jena 07745 Germany
| | - Yury Shebzukhov
- Engelhardt Institute of Molecular Biology Russian Academy of Sciences, Vavilova str. 32 Moscow 119991 Russia
- Charité ‐ Universitätsmedizin Berlin Berlin Institute of Health Center for Regenerative Therapies (BCRT) Berlin 13353 Germany
| | - Radim Šumbera
- Faculty of Science University of South Bohemia České Budějovice 37005 Czech Republic
| | - Satomi Miwa
- Biosciences Institute, Edwardson building, Campus for Ageing and Vitality Newcastle University Newcastle upon Tyne NE4 5PL U.K
| | - Mikhail Y. Vyssokikh
- Belozersky Institute of Physico‐Chemical Biology Lomonosov Moscow State University Moscow 119991 Russia
| | - Thomas Zglinicki
- Biosciences Institute, Edwardson building, Campus for Ageing and Vitality Newcastle University Newcastle upon Tyne NE4 5PL U.K
| | - Olga Averina
- Belozersky Institute of Physico‐Chemical Biology Lomonosov Moscow State University Moscow 119991 Russia
| | - Thomas B. Hildebrandt
- Department of Reproduction Management Leibniz‐Institute for Zoo and Wildlife Research Berlin 10315 Germany
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Evaporative water loss in seven species of fossorial rodents: Does effect of degree of fossoriality and sociality exist? J Therm Biol 2020; 89:102564. [DOI: 10.1016/j.jtherbio.2020.102564] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 02/26/2020] [Accepted: 02/27/2020] [Indexed: 01/09/2023]
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14
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Thermoregulatory differences in African mole-rat species from disparate habitats: Responses and limitations. J Therm Biol 2019; 88:102495. [PMID: 32125983 DOI: 10.1016/j.jtherbio.2019.102495] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 12/06/2019] [Accepted: 12/25/2019] [Indexed: 12/20/2022]
Abstract
Individuals and populations possess physiological adaptations to survive local environmental conditions. To occur in different regions where ambient temperature varies, animals must adopt appropriate thermoregulatory mechanisms. Failure to adjust to environmental challenges may result in species distributional range shifts or decreased viability. African mole-rats (Bathyergidae) occupy various habitats in sub-Saharan Africa from deserts to montane regions to mesic coastal areas. We examined thermoregulatory characteristics of three African mole-rat species originating from disparate (montane, savannah, and arid/semi-arid) habitats. Animals were exposed to various ambient temperatures, whilst core body temperature and the surface temperature of different body parts were measured. Oxygen consumption was determined as a measure of heat production. Core body temperatures of Natal (montane) mole-rats (Cryptomys hottentotus natalensis) increased significantly at ambient temperatures >24.5 °C, while those of the highveld (Cryptomys hottentotus pretoriae) (savannah) and Damaraland (Fukomys damarensis) (arid/semi-arid) mole-rats remained within narrower ranges. In terms of surface temperature variation, while pedal surfaces were important in regulating heat loss in Natal and Damaraland mole-rats at high ambient temperatures, the ventral surface was important for heat dissipation in Damaraland and highveld mole-rats. This study provides evidence of the variation and limitations of thermo-physiological mechanisms for three mole-rat species relative to their habitats. Information on physiological adaptations to particular habitats may inform predictive modelling of species movements, declines, and extinctions in response to a changing environment, such as climate change.
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15
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Šumbera R. Thermal biology of a strictly subterranean mammalian family, the African mole-rats (Bathyergidae, Rodentia) - a review. J Therm Biol 2019; 79:166-189. [DOI: 10.1016/j.jtherbio.2018.11.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 11/09/2018] [Accepted: 11/09/2018] [Indexed: 12/12/2022]
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16
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Wiedenová P, Šumbera R, Jan Okrouhlík. Social thermoregulation and socio-physiological effect in the subterranean Mashona mole-rat (Fukomys darlingi). J Therm Biol 2018; 78:367-373. [DOI: 10.1016/j.jtherbio.2018.10.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Revised: 10/23/2018] [Accepted: 10/27/2018] [Indexed: 10/28/2022]
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17
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Retinal S-opsin dominance in Ansell's mole-rats (Fukomys anselli) is a consequence of naturally low serum thyroxine. Sci Rep 2018. [PMID: 29531249 PMCID: PMC5847620 DOI: 10.1038/s41598-018-22705-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mammals usually possess a majority of medium-wavelength sensitive (M-) and a minority of short-wavelength sensitive (S-) opsins in the retina, enabling dichromatic vision. Unexpectedly, subterranean rodents from the genus Fukomys exhibit an S-opsin majority, which is exceptional among mammals, albeit with no apparent adaptive value. Because thyroid hormones (THs) are pivotal for M-opsin expression and metabolic rate regulation, we have, for the first time, manipulated TH levels in the Ansell's mole-rat (Fukomys anselli) using osmotic pumps. In Ansell's mole-rats, the TH thyroxine (T4) is naturally low, likely as an adaptation to the harsh subterranean ecological conditions by keeping resting metabolic rate (RMR) low. We measured gene expression levels in the eye, RMR, and body mass (BM) in TH-treated animals. T4 treatment increased both, S- and M-opsin expression, albeit M-opsin expression at a higher degree. However, this plasticity was only given in animals up to approximately 2.5 years. Mass-specific RMR was not affected following T4 treatment, although BM decreased. Furthermore, the T4 inactivation rate is naturally higher in F. anselli compared to laboratory rodents. This is the first experimental evidence that the S-opsin majority in Ansell's mole-rats is a side effect of low T4, which is downregulated to keep RMR low.
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18
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Schielke CKM, Burda H, Henning Y, Okrouhlík J, Begall S. Higher resting metabolic rate in long-lived breeding Ansell's mole-rats ( Fukomys anselli). Front Zool 2017; 14:45. [PMID: 29018488 PMCID: PMC5610445 DOI: 10.1186/s12983-017-0229-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Accepted: 09/14/2017] [Indexed: 01/27/2023] Open
Abstract
Background Reproduction is an energetically expensive process that supposedly impairs somatic integrity in the long term, because resources are limited and have to be allocated between reproduction and somatic maintenance, as predicted by the life history trade-off model. The consequence of reduced investment in somatic maintenance is a gradual deterioration of function, i.e. senescence. However, this classical trade-off model gets challenged by an increasing number of contradicting studies. Here we report about an animal model, which adds more complexity to the ongoing debate. Ansell’s mole-rats are long-lived social subterranean rodents with only the founder pair reproducing, while most of their offspring remain in the parental burrow system and do not breed. Despite of a clear reproductive trade-off, breeders live up to twice as long as non-breeders, a unique feature amongst mammals. Methods We investigated mass-specific resting metabolic rates (msRMR) of breeders and non-breeders to gain information about the physiological basis underlying the reproduction-associated longevity in Ansell’s mole-rats. We assessed the thermoneutral zone (TNZ) for breeders and non-breeders separately by means of indirect calorimetry. We applied generalized linear mixed-effects models for repeated measurements using the msRMR in the respective TNZs. Results TNZ differed between reproductive and non-reproductive Ansell’s mole-rats. Contrary to classical aging models, the shorter-lived non-breeders had significantly lower msRMR within the thermoneutral zone compared to breeders. Conclusion This is the first study reporting a positive correlation between msRMR and lifespan based on reproductive status. Our finding contradicts common aging theories, but supports recently introduced models which do not necessarily link reproductive trade-offs to lifespan reduction.
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Affiliation(s)
| | - Hynek Burda
- Faculty of Biology, University of Duisburg-Essen, Essen, Germany.,Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Praha, Czech Republic
| | | | - Jan Okrouhlík
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Sabine Begall
- Faculty of Biology, University of Duisburg-Essen, Essen, Germany
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Genoud M, Isler K, Martin RD. Comparative analyses of basal rate of metabolism in mammals: data selection does matter. Biol Rev Camb Philos Soc 2017; 93:404-438. [PMID: 28752629 DOI: 10.1111/brv.12350] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 05/29/2017] [Accepted: 06/05/2017] [Indexed: 12/21/2022]
Abstract
Basal rate of metabolism (BMR) is a physiological parameter that should be measured under strictly defined experimental conditions. In comparative analyses among mammals BMR is widely used as an index of the intensity of the metabolic machinery or as a proxy for energy expenditure. Many databases with BMR values for mammals are available, but the criteria used to select metabolic data as BMR estimates have often varied and the potential effect of this variability has rarely been questioned. We provide a new, expanded BMR database reflecting compliance with standard criteria (resting, postabsorptive state; thermal neutrality; adult, non-reproductive status for females) and examine potential effects of differential selectivity on the results of comparative analyses. The database includes 1739 different entries for 817 species of mammals, compiled from the original sources. It provides information permitting assessment of the validity of each estimate and presents the value closest to a proper BMR for each entry. Using different selection criteria, several alternative data sets were extracted and used in comparative analyses of (i) the scaling of BMR to body mass and (ii) the relationship between brain mass and BMR. It was expected that results would be especially dependent on selection criteria with small sample sizes and with relatively weak relationships. Phylogenetically informed regression (phylogenetic generalized least squares, PGLS) was applied to the alternative data sets for several different clades (Mammalia, Eutheria, Metatheria, or individual orders). For Mammalia, a 'subsampling procedure' was also applied, in which random subsamples of different sample sizes were taken from each original data set and successively analysed. In each case, two data sets with identical sample size and species, but comprising BMR data with different degrees of reliability, were compared. Selection criteria had minor effects on scaling equations computed for large clades (Mammalia, Eutheria, Metatheria), although less-reliable estimates of BMR were generally about 12-20% larger than more-reliable ones. Larger effects were found with more-limited clades, such as sciuromorph rodents. For the relationship between BMR and brain mass the results of comparative analyses were found to depend strongly on the data set used, especially with more-limited, order-level clades. In fact, with small sample sizes (e.g. <100) results often appeared erratic. Subsampling revealed that sample size has a non-linear effect on the probability of a zero slope for a given relationship. Depending on the species included, results could differ dramatically, especially with small sample sizes. Overall, our findings indicate a need for due diligence when selecting BMR estimates and caution regarding results (even if seemingly significant) with small sample sizes.
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Affiliation(s)
- Michel Genoud
- Department of Ecology and Evolution, University of Lausanne, CH-1015, Lausanne, Switzerland.,Division of Conservation Biology, Institute of Ecology and Evolution, Department of Biology, University of Bern, CH-3012, Bern, Switzerland
| | - Karin Isler
- Department of Anthropology, University of Zürich-Irchel, CH-8057, Zürich, Switzerland
| | - Robert D Martin
- Integrative Research Center, The Field Museum, Chicago, IL, 60605-2496, U.S.A.,Institute of Evolutionary Medicine, University of Zürich-Irchel, CH-8057, Zürich, Switzerland
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20
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Gomes Rodrigues H, Šumbera R. Dental peculiarities in the silvery mole-rat: an original model for studying the evolutionary and biological origins of continuous dental generation in mammals. PeerJ 2015; 3:e1233. [PMID: 26401449 PMCID: PMC4579028 DOI: 10.7717/peerj.1233] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Accepted: 08/18/2015] [Indexed: 11/20/2022] Open
Abstract
Unravelling the evolutionary and developmental mechanisms that have impacted the mammalian dentition, since more than 200 Ma, is an intricate issue. Interestingly, a few mammal species, including the silvery mole-rat Heliophobius argenteocinereus, are able to replace their dentition by the addition of supernumerary molars at the back of jaw migrating then toward the front. The aim here was to demonstrate the potential interest of further studying this rodent in order to better understand the origins of continuous dental replacement in mammals, which could also provide interesting data concerning the evolution of limited dental generation occurring in first mammals. In the present study, we described the main stages of the dental eruptive sequence in the silvery mole-rat and the associated characteristics of horizontal replacement using X-ray microtomography. This was coupled to the investigation of other African mole-rats which have no dental replacement. This method permitted to establish evidence that the initial development of the dentition in Heliophobius is comparable to what it is observed in most of African mole-rats. This rodent first has premolars, but then identical additional molars, a mechanism convergent to manatees and the pygmy rock-wallaby. Evidence of continuous replacement and strong dental dynamics were also illustrated in Heliophobius, and stressed the need to deeply investigate these aspects for evolutionary, functional and developmental purposes. We also noticed that two groups of extinct non-mammalian synapsids convergently acquired this dental mechanism, but in a way differing from extant mammals. The discussion on the diverse evolutionary origins of horizontal dental replacement put emphasis on the necessity of focusing on biological parameters potentially involved in both continuous and limited developments of teeth in mammals. In that context, the silvery mole-rat could appear as the most appropriate candidate to do so.
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Affiliation(s)
- Helder Gomes Rodrigues
- Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements (CR2P), UMR CNRS 7207, Museum national d'Histoire naturelle, Université Paris 6 , Paris , France
| | - Radim Šumbera
- Department of Zoology, Faculty of Science, University of South Bohemia , České Budějovice , Czech Republic
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21
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Gomes Rodrigues H, Šumbera R, Hautier L. Life in Burrows Channelled the Morphological Evolution of the Skull in Rodents: the Case of African Mole-Rats (Bathyergidae, Rodentia). J MAMM EVOL 2015. [DOI: 10.1007/s10914-015-9305-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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22
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Begall S, Berendes M, Schielke CKM, Henning Y, Laghanke M, Scharff A, van Daele P, Burda H. Temperature preferences of African mole-rats (family Bathyergidae). J Therm Biol 2015; 53:15-22. [PMID: 26590451 DOI: 10.1016/j.jtherbio.2015.08.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 08/04/2015] [Accepted: 08/04/2015] [Indexed: 11/15/2022]
Abstract
Many animals are able to detect small temperature differences and show strong temperature preferences during periods of rest and activity. Mammals inhabiting the subterranean ecotope can adapt their digging and foraging activity in shallow tunnels temporarily to periods with favourable ambient air and soil temperatures. Moreover, subterranean mammals have the unique opportunity to select for their nests in soil depths with certain, daily and seasonally constant temperatures. Our knowledge on nest temperatures in several species of subterranean mammals is based on measurements of temperatures in empty nests. We can expect, however, that the temperature in an occupied nest is higher (due to the "igloo effect"). We performed two experiments regarding the temperature preference in five species of African mole-rats (Bathyergidae, Rodentia: Fukomys anselli, F. mechowii, F. micklemi, Heliophobius argenteocinereus, and Heterocephalus glaber). In a first experiment, the animals were tested pairwise (except for the solitary silvery mole-rats, H. argenteocinereus, that were tested singly) in an apparatus consisting of seven chambers with a temperature gradient ranging between 16 and 37°C (air temperature). While the smaller species (<110g; F. anselli, F. micklemi, H. glaber) chose chambers with average air temperatures around 29°C, the larger mole-rats rested preferably at lower temperatures of approximately 25.6°C (F. mechowii) and 27.7°C (H. argenteocinereus). A strong negative correlation between body mass and preferred air temperature was detected across species. Thus, the results comply with the surface-volume-rule. Contrary to expectations, temperature preference of naked mole-rats (H. glaber) did not deviate from those of furred small mole-rats, but followed the general trend with smaller species preferring higher temperatures. In a second experiment, Ansell's mole-rats (F. anselli) were tested in groups of four, six and nine animals and the preferred temperatures were compared to the values obtained for pairs. The preferred mean air temperatures did not differ among the groups of different sizes. We discuss our findings in the light of ecophysiological adaptations to cope with the ambient conditions proposed by the "thermal stress hypothesis". Furthermore, we suggest that while soil temperature is decisive during digging as the mole-rats warm up or cool due to tight contact between body and soil (conduction), resting animals prevent heat loss through conduction by building a nest.
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Affiliation(s)
- Sabine Begall
- Department of General Zoology, Institute for Biology, Faculty of Biology, University of Duisburg-Essen, Universitätsstr. 5, D-45117 Essen, Germany.
| | - Meike Berendes
- Department of General Zoology, Institute for Biology, Faculty of Biology, University of Duisburg-Essen, Universitätsstr. 5, D-45117 Essen, Germany
| | - Charlotte K M Schielke
- Department of General Zoology, Institute for Biology, Faculty of Biology, University of Duisburg-Essen, Universitätsstr. 5, D-45117 Essen, Germany
| | - Yoshiyuki Henning
- Department of General Zoology, Institute for Biology, Faculty of Biology, University of Duisburg-Essen, Universitätsstr. 5, D-45117 Essen, Germany
| | - Marzena Laghanke
- Department of General Zoology, Institute for Biology, Faculty of Biology, University of Duisburg-Essen, Universitätsstr. 5, D-45117 Essen, Germany
| | - Andreas Scharff
- Department of General Zoology, Institute for Biology, Faculty of Biology, University of Duisburg-Essen, Universitätsstr. 5, D-45117 Essen, Germany
| | - Paul van Daele
- Department of Vertebrate Morphology, Ghent University, B-9000 Ghent, Belgium
| | - Hynek Burda
- Department of General Zoology, Institute for Biology, Faculty of Biology, University of Duisburg-Essen, Universitätsstr. 5, D-45117 Essen, Germany
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23
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Okrouhlík J, Burda H, Kunc P, Knížková I, Šumbera R. Surprisingly low risk of overheating during digging in two subterranean rodents. Physiol Behav 2015; 138:236-41. [DOI: 10.1016/j.physbeh.2014.10.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 10/28/2014] [Accepted: 10/30/2014] [Indexed: 10/24/2022]
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24
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Henning Y, Vole C, Begall S, Bens M, Broecker-Preuss M, Sahm A, Szafranski K, Burda H, Dammann P. Unusual ratio between free thyroxine and free triiodothyronine in a long-lived mole-rat species with bimodal ageing. PLoS One 2014; 9:e113698. [PMID: 25409169 PMCID: PMC4237498 DOI: 10.1371/journal.pone.0113698] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 10/27/2014] [Indexed: 12/03/2022] Open
Abstract
Ansell's mole-rats (Fukomys anselli) are subterranean, long-lived rodents, which live in eusocial families, where the maximum lifespan of breeders is twice as long as that of non-breeders. Their metabolic rate is significantly lower than expected based on allometry, and their retinae show a high density of S-cone opsins. Both features may indicate naturally low thyroid hormone levels. In the present study, we sequenced several major components of the thyroid hormone pathways and analyzed free and total thyroxine and triiodothyronine in serum samples of breeding and non-breeding F. anselli to examine whether a) their thyroid hormone system shows any peculiarities on the genetic level, b) these animals have lower hormone levels compared to euthyroid rodents (rats and guinea pigs), and c) reproductive status, lifespan and free hormone levels are correlated. Genetic analyses confirmed that Ansell's mole-rats have a conserved thyroid hormone system as known from other mammalian species. Interspecific comparisons revealed that free thyroxine levels of F. anselli were about ten times lower than of guinea pigs and rats, whereas the free triiodothyronine levels, the main biologically active form, did not differ significantly amongst species. The resulting fT4:fT3 ratio is unusual for a mammal and potentially represents a case of natural hypothyroxinemia. Comparisons with total thyroxine levels suggest that mole-rats seem to possess two distinct mechanisms that work hand in hand to downregulate fT4 levels reliably. We could not find any correlation between free hormone levels and reproductive status, gender or weight. Free thyroxine may slightly increase with age, based on sub-significant evidence. Hence, thyroid hormones do not seem to explain the different ageing rates of breeders and non-breeders. Further research is required to investigate the regulatory mechanisms responsible for the unusual proportion of free thyroxine and free triiodothyronine.
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Affiliation(s)
- Yoshiyuki Henning
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
- * E-mail:
| | - Christiane Vole
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
| | - Sabine Begall
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
| | - Martin Bens
- Genome Analysis, Leibniz Institute for Age Research - Fritz Lipmann Institute, Jena, Germany
| | - Martina Broecker-Preuss
- Department of Endocrinology and Metabolism and Division of Laboratory Research, University Hospital, University of Duisburg-Essen, Essen, Germany
| | - Arne Sahm
- Genome Analysis, Leibniz Institute for Age Research - Fritz Lipmann Institute, Jena, Germany
| | - Karol Szafranski
- Genome Analysis, Leibniz Institute for Age Research - Fritz Lipmann Institute, Jena, Germany
| | - Hynek Burda
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
| | - Philip Dammann
- Department of General Zoology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
- Central Animal Laboratory, University Hospital, University of Duisburg-Essen, Essen, Germany
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25
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Šklíba J, Lövy M, Hrouzková E, Kott O, Okrouhlík J, Šumbera R. Social and Environmental Influences on Daily Activity Pattern in Free-Living Subterranean Rodents. J Biol Rhythms 2014; 29:203-214. [DOI: 10.1177/0748730414526358] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Predictable daily activity patterns have been detected repeatedly even in mammals living in stable environments, as is the case for subterranean rodents. Whereas studies on activity of these rodents under laboratory conditions almost exclusively have concerned themselves with the influence of light, many field studies have revealed signs of an association between the activity pattern and daily fluctuations of temperature under the ground. This would assume that behavioral thermoregulation is probably involved. The only exceptions to the relationship between temperature and activity are 2 eusocial mole-rats of the genus Fukomys (Bathyergidae, Rodentia), which indicates that activity patterns could be affected also by social cues. To better understand how social and environmental factors influence the activity pattern in a eusocial mole-rat, we monitored the outside-nest activity in another species of this genus, the Ansell’s mole-rat ( Fukomys anselli), which has a relatively small body mass, high conductance, and more superficially situated burrows. Its daily activity had 1 prominent peak (around 1400 h), and it was tightly correlated with the temperature measured at depth of foraging burrows. Since F. anselli has high thermoregulatory requirements to maintain stable body temperature below the lower critical temperature, we conclude that the observed pattern is probably the result of minimizing the cost of thermoregulation. There were no significant differences in the daily activity patterns of breeding males and females and nonbreeders. Members of the same family group tended to have more similar activity patterns, but consistent activity synchronization between individuals was not proven. From the comparison of available data on all subterranean rodents, we assume that social cues in communally nesting mole-rats may disrupt (mask) temperature-related daily activity rhythms but probably only if the additional cost of thermoregulation is not too high, as it likely is in the Ansell’s mole-rat.
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Affiliation(s)
- Jan Šklíba
- Department of Zoology, Faculty of Science, University of South Bohemia, Cˇeské Budeˇjovice, Czech Republic
| | - Matěj Lövy
- Department of Zoology, Faculty of Science, University of South Bohemia, Cˇeské Budeˇjovice, Czech Republic
| | - Ema Hrouzková
- Department of Zoology, Faculty of Science, University of South Bohemia, Cˇeské Budeˇjovice, Czech Republic
| | - Ondřej Kott
- Department of Zoology, Faculty of Science, University of South Bohemia, Cˇeské Budeˇjovice, Czech Republic
| | - Jan Okrouhlík
- Department of Zoology, Faculty of Science, University of South Bohemia, Cˇeské Budeˇjovice, Czech Republic
| | - Radim Šumbera
- Department of Zoology, Faculty of Science, University of South Bohemia, Cˇeské Budeˇjovice, Czech Republic
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Zemanová M, Šumbera R, Okrouhlík J. Poikilothermic traits in Mashona mole-rat (Fukomys darlingi). Reality or myth? J Therm Biol 2012. [DOI: 10.1016/j.jtherbio.2012.04.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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27
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Schielke CK, Begall S, Burda H. Reproductive state does not influence activity budgets of eusocial Ansell's mole-rats, Fukomys anselli (Rodentia, Bathyergidae): A study of locomotor activity by means of RFID. Mamm Biol 2012. [DOI: 10.1016/j.mambio.2011.09.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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28
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Oliveriusová L, Němec P, Králová Z, Sedláček F. Magnetic compass orientation in two strictly subterranean rodents: learned or species-specific innate directional preference? J Exp Biol 2012; 215:3649-54. [DOI: 10.1242/jeb.069625] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Summary
Evidence for magnetoreception in mammals remains limited. Magnetic compass orientation or magnetic alignment has been conclusively demonstrated in only a handful of mammalian species. The functional properties and underlying mechanisms have been most thoroughly characterized in Ansell's mole-rat, Fukomys anselli, which is the species of choice due to its spontaneous drive to construct nests in the south-eastern sector of a circular arena using the magnetic field azimuth as the primary orientation cue. Due to the remarkable consistency between experiments, it is generally believed that this directional preference is innate. To test the hypothesis that spontaneous south-eastern directional preference is a shared, ancestral feature of all African mole rats (Bathyergidae, Rodentia), we employed the same arena assay to study magnetic orientation in two other mole-rat species, the social giant mole-rat Fukomys mechowii and the solitary silvery mole-rat Heliophobius argenteocinereus. Both species exhibited spontaneous western directional preference and deflected their directional preference according to shifts in the direction of magnetic north, clearly indicating that they were deriving directional information from the magnetic field. Because all of the experiments were performed in total darkness, our results strongly suggest that all African mole rats use a light-independent magnetic compass for near-space orientation. However, the spontaneous directional preference is not common and may be either innate but species-specific, or learned. We propose an experiment that should be performed to distinguish between these two alternatives.
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Bhagwandin A, Gravett N, Hemingway J, Oosthuizen M, Bennett N, Siegel J, Manger P. Orexinergic neuron numbers in three species of African mole rats with rhythmic and arrhythmic chronotypes. Neuroscience 2011; 199:153-65. [DOI: 10.1016/j.neuroscience.2011.10.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Revised: 10/06/2011] [Accepted: 10/13/2011] [Indexed: 10/16/2022]
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Streicher S, Boyles JG, Oosthuizen MK, Bennett NC. Body temperature patterns and rhythmicity in free-ranging subterranean Damaraland mole-rats, Fukomys damarensis. PLoS One 2011; 6:e26346. [PMID: 22028861 PMCID: PMC3196572 DOI: 10.1371/journal.pone.0026346] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 09/25/2011] [Indexed: 11/25/2022] Open
Abstract
Body temperature (Tb) is an important physiological component that affects endotherms from the cellular to whole organism level, but measurements of Tb in the field have been noticeably skewed towards heterothermic species and seasonal comparisons are largely lacking. Thus, we investigated patterns of Tb patterns in a homeothermic, free-ranging small mammal, the Damaraland mole-rat (Fukomys damarensis) during both the summer and winter. Variation in Tb was significantly greater during winter than summer, and greater among males than females. Interestingly, body mass had only a small effect on variation in Tb and there was no consistent pattern relating ambient temperature to variation in Tb. Generally speaking, it appears that variation in Tb patterns varies between seasons in much the same way as in heterothermic species, just to a lesser degree. Both cosinor analysis and Fast Fourier Transform analysis revealed substantial individual variation in Tb rhythms, even within a single colony. Some individuals had no Tb rhythms, while others appeared to exhibit multiple rhythms. These data corroborate previous laboratory work showing multiplicity of rhythms in mole-rats and suggest the variation seen in the laboratory is a true indicator of the variation seen in the wild.
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Affiliation(s)
- Sonja Streicher
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Justin G. Boyles
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- * E-mail:
| | - Maria K. Oosthuizen
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Nigel C. Bennett
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- Department of Zoology, King Saud University, Riyadh, Saudi Arabia
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Lövy M, Šklíba J, Burda H, Chitaukali WN, Šumbera R. Ecological characteristics in habitats of two African mole-rat species with different social systems in an area of sympatry: implications for the mole-rat social evolution. J Zool (1987) 2011. [DOI: 10.1111/j.1469-7998.2011.00860.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- M. Lövy
- Faculty of Science; University of South Bohemia; České Budějovice; Czech Republic
| | - J. Šklíba
- Faculty of Science; University of South Bohemia; České Budějovice; Czech Republic
| | - H. Burda
- Faculty of Biology; University of Duisburg-Essen; Essen; Germany
| | - W. N. Chitaukali
- Biology Department; Chancellor College; University of Malawi; Zomba; Malawi
| | - R. Šumbera
- Faculty of Science; University of South Bohemia; České Budějovice; Czech Republic
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Zelová J, Šumbera R, Okrouhlík J, Šklíba J, Lövy M, Burda H. A seasonal difference of daily energy expenditure in a free-living subterranean rodent, the silvery mole-rat (Heliophobius argenteocinereus; Bathyergidae). Comp Biochem Physiol A Mol Integr Physiol 2011; 158:17-21. [DOI: 10.1016/j.cbpa.2010.07.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 06/29/2010] [Accepted: 07/02/2010] [Indexed: 10/19/2022]
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Zelová J, Šumbera R, Okrouhlík J, Burda H. Cost of digging is determined by intrinsic factors rather than by substrate quality in two subterranean rodent species. Physiol Behav 2010; 99:54-8. [DOI: 10.1016/j.physbeh.2009.10.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 10/06/2009] [Accepted: 10/07/2009] [Indexed: 10/20/2022]
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Nathaniel TI, Saras A, Umesiri FE, Olajuyigbe F. Tolerance to oxygen nutrient deprivation in the hippocampal slices of the naked mole rats. J Integr Neurosci 2009; 8:123-36. [PMID: 19618484 DOI: 10.1142/s0219635209002149] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Accepted: 05/04/2009] [Indexed: 11/18/2022] Open
Abstract
Hypoxia tolerance in the naked mole rats (Heterocephalus glaber) represents a unique physiological phenomenon characterized by the capability to regulate oxygen demand to attenuate energetically costly response to low oxygen condition. Several aspects of tolerance to hypoxia in the naked mole rat are consistent with a state of neuroprotection; however, it remains to be established if such protective capability is expressed in the brain cells of mole rats subjected to hypoxia insults. The objective of this study was to determine whether evidence of tolerance to oxygen nutrient deprivation exists in the chronic cultures of the naked mole rats hippocampal slices. We used oxygen nutrient deprivation (OND), an in vitro model of hypoxia tolerance, to determine neuronal survival in the hippocampal slices of mole rats and rats (Rattus sp.). Our results indicate that hippocampal slices of mole rats kept in hypoxic condition consistently tolerate OND right from the onset time of 5 hrs and the tolerance to OND is maintained for 24 hrs, suggesting that there is evidence of tolerance to OND in hippocampal slices of mole rats.
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Affiliation(s)
- Thomas I Nathaniel
- Center for Natural and Health Sciences, Science Department, Marywood University, 2300 Adams Avenue, Scranton, PA 18509, USA.
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Luna F, Antenucci C, Bozinovic F. Comparative Energetics of the SubterraneanCtenomysRodents: Breaking Patterns. Physiol Biochem Zool 2009; 82:226-35. [DOI: 10.1086/597526] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Sumbera R, Zelová J, Kunc P, Knízková I, Burda H. Patterns of surface temperatures in two mole-rats (Bathyergidae) with different social systems as revealed by IR-thermography. Physiol Behav 2007; 92:526-32. [PMID: 17544016 DOI: 10.1016/j.physbeh.2007.04.029] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2007] [Revised: 04/16/2007] [Accepted: 04/23/2007] [Indexed: 11/26/2022]
Abstract
Furred subterranean mammals face the problem of dissipating heat to the environment because high humidity and absence of air flow in sealed belowground tunnels constrain heat loss from body by convection and evaporation. In order to detect body areas responsible for heat loss, surface temperatures in two species of African mole-rats were measured at different ambient air temperatures by infrared thermography. Fur characteristics were also evaluated. Thinner pelage of the ventrum, its moderate temperature and large size suggest that ventral side of the body is the main thermal avenue for heat loss in both species. Interspecific differences could be explained by different fur characteristics connected with social thermoregulation. Compared to the social Fukomys mechowii, the solitary Heliophobius argenteocinereus has denser and longer fur on most of its body; its surface temperature was thus lower than in F. mechowii at lowered ambient temperatures. On the other hand, the denser and longer hair cover in H. argenteocinereus impedes heat dissipation at highest ambient temperatures (and probably also during digging activity) resulting in increase of core body temperature. H. argenteocinereus seems to be more sensitive to overheating than F. mechowii. At lower air temperatures, the social species may uses huddling to combat hypothermia.
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Affiliation(s)
- Radim Sumbera
- Department of Zoology, Faculty of Biological Sciences, University of South Bohemia, Branisovská 31, 370 05, Ceské Budejovice, Czech Republic.
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