Is the naked mole-rat Hererocephalus glaber an endothermic yet poikilothermic mammal? - ScienceDirect

Journal of Thermal Biology

Volume 16, Issue 4, July 1991, Pages 227-232

Journal of Thermal Biology

https://doi.org/10.1016/0306-4565(91)90030-6 Get rights and content

Abstract

1.
1. Thermoregulatory changes with ambient temperature (T_a) were monitored in Heterocephalus glaber between 12 and 37°C.
2.
2. At all T_as monitored, body temperature (T_b) was directly proportional to T_a (T_b = 0.568 + 10016 T_a).
3.
3. Below T_a 29°C, V̇O₂ varied in a typically poikilothermic pattern, whereas above 29°C, V̇O₂ followed a typically endothermic pattern.
4.
4. At T_as between 31 and 34°C, V̇O₂ was minimal (1.00 ± 0.09 ml/g/h), skin temperature was 1.8 ± 0.6°C lower than T_b and evaporative water loss accounted for 173.7 ± 51.0% of the metabolic heat produced.
5.
5. The high rates of heat transfer are such that individual naked mole-rats cannot regulate T_b over the entire range of measured T_as and, as such, are poikilothermic mammals.

References (39)

R. Buffenstein
The importance of microhabitat in thermoregulation and thermal conductance in two Namib rodents—a creative dweller, Aethomys namaquensis, and burrow dweller
Gerbillurus paeba. J. therm. Biol.
(1984)
R.M. Chew et al.
Development of metabolic response to cold in young mice of four species
Comp. Biochem. Physiol.
(1967)
G.N. Louw et al.
Effect of thyroxine and noradrenaline on thermoregulation, cardiac rate and oxygen consumption in the Monitor lizard, Varanus Albigularis
J. therm. Biol.
(1976)
P.C. Withers et al.
The effect of huddling on thermoregulation and oxygen consumption for the naked mole-rat
Comp. Biochem. Physiol.
(1980)
IUPS Thermal Commission
Glossary of terms for thermal physiology
Fftügers Arch.
(1987)
R. Arieli et al.
Metabolic responses of fossorial rodent (Spalax ehrenbergi) to simulated burrow conditions
Physiol. Zool.
(1977)
N.B. Bennett et al.
Daily and seasonal temperatures in the burrows of African rodent moles
S. Afr. J. Zool.
(1988)
J. Bligh
R. Buffenstein et al.
Thermoregulation and metabolism in the smallest African gerbil
Gerbillus pusillus. J. Zool. Lond.
(1985)
L.C. Contreras et al.
Thermo-regulation and energetics in subterranean mammals

G. De Graaff

F. Depocas et al.

Use of the Pauling oxygen analyser for measurement of oxygen consumption of animals in open circuit systems and in a short-lag closed-circuit apparatus

J. appl. Physiol.

(1957)

P. Gorou

F.R. Hainsworth et al.

Regulation of oxygen consumption and body temperature during torpor in a hummingbird

Eulampis jugularis. Science

(1970)

J. Hart

Rodents

G. Heldmaier et al.

Seasonal pattern and the energetics of short daily torpor in the Djungarian hamster

Phodopus sangorus. Oecologia

(1981)

H.C. Heller

Measurements of convective and radiative heat transfer in small mammals

J. Mammal.

(1972)

H.W. Hudson

Shallow daily torpor: a thermoregulatory adaptation

J.U.M. Jarvis

Eusociality in a mammal: cooperative breeding in naked mole-rat colonies

Science

(1981)

Cited by (172)

Together or alone? Huddling energetic savings in three social mole-rat species of genus Fukomys. A dispersal perspective
2022, Journal of Thermal Biology
African mole-rats (Bathyergidae) are strictly subterranean rodents distributed in sub-Saharan Africa. Although the soil layer provides a temperature buffer, the temperature in their burrows is usually below their thermoneutral zone and thermogenesis is necessary to maintain a stable body temperature. In social bathyergids, an important mechanism for decreasing the thermoregulatory cost is social thermoregulation in the form of huddling. The effect of huddling may be of special importance during forming of a new family as only two adults are present and social species are known for higher heat losses from their bodies compared to solitary mole-rats.
In our study, we measured the resting metabolic rate and energetic saving in three social bathyergid species which differ in body size. We compared animals that were housed individually and in pairs at two different ambient temperatures (T_a). At a temperature within their TNZ (T_a = 30 °C), no energetic savings were expected, whereas in T_a = 20 °C we expected energetic savings due to huddling.
We found no energetic savings at 30 °C in any of the species, but almost 20% in the two small bodied Fukomys species F. micklemi and F. anselli at 20 °C. In the largest species, F. mechowii, no significant energetic savings were observed. Our results confirm the importance of huddling for the energetic balance of social mole-rats and show that huddling with one partner can bring substantial energetic savings, which can be allocated to other activities such as extension of established burrow systems or reproduction to increase the workforce and fulfill the purpose of dispersal.
Not just a cousin of the naked mole-rat: Damaraland mole-rats offer unique insights into biomedicine
2022, Comparative Biochemistry and Physiology Part - B: Biochemistry and Molecular Biology
Evolutionary medicine has been a fast-growing field of biological research in the past decade. One of the strengths of evolutionary medicine is to use non-traditional model organisms which often exhibit unusual characteristics shaped by natural selection. Studying these unusual traits could provide valuable insight to understand biomedical questions, since natural selection likely discovers solutions to those complex biological problems. Because of many unusual traits, the naked mole-rat (NMR) has attracted attention from different research areas such as aging, cancer, and hypoxia- and hypercapnia-related disorders. However, such uniqueness of NMR physiology may sometimes make the translational study to human research difficult. Damaraland mole-rat (DMR) shares multiple characteristics in common with NMR, but shows higher degree of similarity with human in some aspects of their physiology. Research on DMR could therefore offer alternative insights and might bridge the gap between experimental findings from NMR to human biomedical research. In this review, we discuss studies of DMR as an extension of the current set of model organisms to help better understand different aspects of human biology and disease. We hope to encourage researchers to consider studying DMR together with NMR. By studying these two similar but evolutionarily distinct species, we can harvest the power of convergent evolution and avoid the potential biased conclusions based on life-history of a single species.
Naked mole-rat and Damaraland mole-rat exhibit lower respiration in mitochondria, cellular and organismal levels
2022, Biochimica et Biophysica Acta - Bioenergetics
Naked mole-rats (NMR) and Damaraland mole-rats (DMR) exhibit extraordinary longevity for their body size, high tolerance to hypoxia and oxidative stress and high reproductive output; these collectively defy the concept that life-history traits should be negatively correlated. However, when life-history traits share similar underlying physiological mechanisms, these may be positively associated with each other. We propose that one such potential common mechanism might be the bioenergetic properties of mole-rats. Here, we aim to characterize the bioenergetic properties of two African mole-rats. We adopted a top-down perspective measuring the bioenergetic properties at the organismal, cellular, and molecular level in both species and the biological significance of these properties were compared with the same measures in Siberian hamsters and C57BL/6 mice, chosen for their similar body size to the mole-rat species. We found mole-rats shared several bioenergetic properties that differed from their comparison species, including low basal metabolic rates, a high dependence on glycolysis rather than on oxidative phosphorylation for ATP production, and low proton conductance across the mitochondrial inner membrane. These shared mole-rat features could be a result of evolutionary adaptation to tolerating variable oxygen atmospheres, in particular hypoxia, and may in turn be one of the molecular mechanisms underlying their extremely long lifespans.
Effects of dexamethasone and acetylsalicylic acid on inflammation caused by Complete Freund's adjuvant in the naked mole rat (Heterocephalus glaber)
2022, Heliyon
The naked mole rat (NMR) is a fossorial rodent that has been observed to have a unique nociceptive system in comparison to others. In this study, we explored on characterization of chronic inflammation in the NMR using Complete Freund's adjuvant (CFA) and investigated the effects of dexamethasone and acetylsalicylic acid on the resulting inflammation. The NMRs were injected with 0.1 ml of CFA subcutaneously in the right hind paw, and an equivalent volume of normal saline was injected to the control group. Swelling of the injected right hind limb was observed within 24 h of injection, which involved the tibiotarsal joint, palmar surface and the digits of the injected paw. Swelling persisted for 6 weeks of experimentation and peaked between day 14 and 21. The resulting inflammation affected the mobility, stance and joint rigidity of CFA treated NMRs in comparison to the control group. Treatment of the chronic phase of the inflammation from the 11^th day with dexamethasone and acetylsalicylic acid showed no statistical significance in paw circumference compared to the control group, other than on a few, negligible occasions. The present data showed that CFA was able to induce chronic inflammation in the NMR, and the NMR could thus be established as a model for chronic inflammation. There is, however, need for more sensitive parameters to evaluate the effects of anti-inflammatory drugs.
Effects of hypoxic conditions during the plateau period on pre- and posthatch broiler performance
2022, Poultry Science
Adequate ambient temperature and oxygenation are necessary to maintain normal embryonic development of broilers; however, hypoxia challenge during incubation can aid in improving regulatory plasticity and lead to different phenotypes later in life. This study aimed to examine the effects of moderate hypoxia (O₂ 17%) during the plateau phase on the embryonic physiological parameters and on posthatch performance (growth rate, feed consumption and feed conversion) up to the age of poultry marketing. The study included examined embryos exposed to O₂ 17% for 12 h per day (h/d) from E16 through E18 (designated as 12H), or O₂ 17% continuously, from E16 through E17 (designated as 48H) and a standard incubation control group (21% O₂). Physiological and morphological parameters of embryos and hatched chicks were measured. Male Chicks from all 3 treatment groups were raised under recommended temperature regime, and body weight, feed intake and FCR were recorded on a weekly basis. The intermittent hypoxia protocol (12H), allowed embryos to properly adapt to the shortage of oxygen, compensate for the gap in body mass that developed following the first exposure window, and hatch with characteristics similar to those of the control embryos. In contrast, while the 48H embryos were able to adapt to the hypoxic stress, the prolonged exposure prevented them from catching up with both control and 12H embryos. Broilers that were subjected to hypoxia showed hatchling body weights and growth rates similar to those of controls, throughout the entire growth phase. During the fifth wk, lower feed consumption was observed in the 12H and 48H groups and became significantly lower than the control chicks in the sixth wk of growth. Following hypoxia exposure, chicks managed to reach normal body weight with less feed, with the 12H group demonstrating lower and more efficient FCR during the last 2 wk of growth.
Broiler embryos reacted to plateau-phase hypoxia challenge with numerous physiological and metabolic modifications. The prudent alterations in metabolism and cardiovascular system during exposure to hypoxia and posthatch, resulted in more efficient energy utilization in broilers, which may have a long-lasting enhancing effect on posthatching thermotolerance and sustainability in chicks reared under sub-optimal environmental conditions.
Brain extracellular space of the naked mole-rat expands and maintains normal diffusion under ischemic conditions
2021, Brain Research
Brain extracellular space (ECS) forms a conduit for diffusion, an essential mode of molecular transport between brain vasculature, neurons and glia. ECS volume is reduced under conditions of hypoxia and ischemia, contributing to impaired extracellular diffusion and consequent neuronal dysfunction and death. We investigated the ECS volume fraction and diffusion permeability of the African naked mole-rat (NM-R; Heterocephalus Glaber), a rodent with a remarkably high tolerance for hypoxia and ischemia. Real-Time Iontophoretic and Integrative Optical Imaging methods were used to evaluate diffusion transport in cortical slices under normoxic and ischemic conditions, and results were compared to values previously collected in rats. NM-R brains under normoxic conditions had a smaller ECS volume fraction than rats, and a correspondingly decreased diffusion permeability for macromolecules. Surprisingly, and in sharp contrast to rats, the NM-R ECS responded to ischemic conditions at the center of thick brain slices by expanding, rather than shrinking, and preserving diffusion permeabilities for small and large molecules. The NM-R thick slices also showed a blunted accumulation of ECS potassium compared to rats. The remarkable dynamic response of the NM-R ECS to ischemia likely demonstrates an adaptation for NM-R to maintain brain function in their extreme nest environment.

View all citing articles on Scopus

Copyright © 1991 Published by Elsevier Ltd.

Bowhead Whale: Balaena mysticetus
Encyclopedia of Marine Mammals, 2018, pp. 133-135
J. Craig George, …, R. Suydam
Rethinking the dental morphological differences between domestic equids
Journal of Archaeological Science, Volume 101, 2019, pp. 140-148
Richard Chuang, Vincent Bonhomme
Prediction of Adipose Browning Capacity by Systematic Integration of Transcriptional Profiles
Cell Reports, Volume 23, Issue 10, 2018, pp. 3112-3125
Yiming Cheng, …, Fabiana Perocchi
DNA analysis of ancient dogs of the Americas: Identifying possible founding haplotypes and reconstructing population histories
Journal of Human Evolution, Volume 79, 2015, pp. 105-118
Kelsey E. Witt, …, Ripan S. Malhi
Diverse phylogenomic datasets uncover a concordant scenario of laurasiatherian interordinal relationships
Molecular Phylogenetics and Evolution, Volume 157, 2021, Article 107065
Xue Lv, …, Li Yu
Citizen science: A new direction in canine behavior research
Behavioural Processes, Volume 110, 2015, pp. 125-132
Julie Hecht, Eleanor Spicer Rice