Surprisingly low risk of overheating during digging in two subterranean rodents

Okrouhlík, Jan; Burda, Hynek; Kunc, P.; Knı́žková, I.; Šumbera, Radim

doi:10.1016/j.physbeh.2014.10.029

Cited by 21 publications

(19 citation statements)

References 46 publications

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“…Considerable attention has been given to the extrinsic and intrinsic factors that might limit energy acquisition and expenditure, such as food availability and the capacity to digest and assimilate food Hammond and Diamond 1997;Speakman 2000;Bacigalupe and Bozinovic 2002), whereas only recently has the putative role of heat dissipation been recognized (but see Greenwood and Wheeler 1985). As a consequence of the heat dissipation limit theory (Speakman and Król 2010a, b), an increasing number of studies are currently assessing how heat dissipation might impact the ecology and evolution of endothermic lineages (e.g., Voigt and Lewanzik 2011;Greenberg et al 2012;Kurnath and Dearing 2013;Larose et al 2013;Zub et al 2013;Okrouhlík et al 2015).…”

Section: Activity and Reproductionmentioning

confidence: 99%

Thermoregulation in endotherms: physiological principles and ecological consequences

Rezende

Bacigalupe

2015

J Comp Physiol B

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In a seminal study published nearly 70 years ago, Scholander et al. (Biol Bull 99:259-271, 1950) employed Newton's law of cooling to describe how metabolic rates (MR) in birds and mammals vary predictably with ambient temperature (T a). Here, we explore the theoretical consequences of Newton's law of cooling and show that a thermoregulatory polygon provides an intuitively simple and yet useful description of thermoregulatory responses in endothermic organisms. This polygon encapsulates the region in which heat production and dissipation are in equilibrium and, therefore, the range of conditions in which thermoregulation is possible. Whereas the typical U-shaped curve describes the relationship between T a and MR at rest, thermoregulatory polygons expand this framework to incorporate the impact of activity, other behaviors and environmental conditions on thermoregulation and energy balance. We discuss how this framework can be employed to study the limits to effective thermoregulation and their ecological repercussions, allometric effects and residual variation in MR and thermal insulation, and how thermoregulatory requirements might constrain locomotor or reproductive performance (as proposed, for instance, by the heat dissipation limit theory). In many systems the limited empirical knowledge on how organismal traits may respond to environmental changes prevents physiological ecology from becoming a fully developed predictive science. In endotherms, however, we contend that the lack of theoretical developments that translate current physiological understanding into formal mechanistic models remains the main impediment to study the ecological and evolutionary repercussions of thermoregulation. In spite of the inherent limitations of Newton's law of cooling as an oversimplified description of the mechanics of heat transfer, we argue that understanding how systems that obey this approximation work can be enlightening on conceptual grounds and relevant as an analytical and predictive tool to study ecological phenomena. As such, the proposed approach may constitute a powerful tool to study the impact of thermoregulatory constraints on variables related to fitness, such as survival and reproductive output, and help elucidating how species will be affected by ongoing climate change.

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Section: Activity and Reproductionmentioning

confidence: 99%

Thermoregulation in endotherms: physiological principles and ecological consequences

Rezende

Bacigalupe

2015

J Comp Physiol B

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“…It was speculated that in subterranean mammals, the ventral body surface is relevant for heat dissipation as indicated by its shorter and less dense fur (Cutrera & Antenucci, 2004;Šumbera et al, 2007). In two species of African mole-rats (Bathyergidae), the silvery mole-rat Heliophobius argenteocinereus and the giant mole-rat Fukomys mechowii, the importance of the less furred ventral body part as the main thermal window was supported also by infrared thermography (Šumbera et al, 2007;Okrouhlík et al, 2015). Recently, the higher surface temperature of the ventral body part in a wide gradient of experimental ambient temperatures was confirmed in other species of subterranean rodents from different phylogenetic lineages (F. Vejmělka and R. Šumbera, 2017, unpublished data).…”

Section: Introductionmentioning

confidence: 99%

Functional histology of the skin in the subterranean African giant mole-rat: thermal windows are determined solely by pelage characteristics

Pleštilová

Okrouhlík

Burda

et al. 2020

PeerJ

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Excavation of burrows is an extremely physically demanding activity producing a large amount of metabolic heat. Dissipation of its surplus is crucial to avoid the risk of overheating, but in subterranean mammals it is complicated due to the absence of notable body extremities and high humidity in their burrows. IR-thermography in a previous study on two species of African mole-rats revealed that body heat was dissipated mainly through the ventral body part, which is notably less furred. Here, we analyzed the dorsal and ventral skin morphology, to test if dermal characteristics could contribute to higher heat dissipation through the ventral body part. The thickness of the epidermis and dermis and the presence, extent and connectivity of fat tissue in the dermis were examined using routine histological methods, while vascular density was evaluated using fluorescent dye and confocal microscopy in the giant mole-rat Fukomys mechowii. As in other hitherto studied subterranean mammals, no subcutaneous adipose tissue was found. All examined skin characteristics were very similar for both dorsal and ventral regions: relative content of adipose tissue in the dermis (14.4 ± 3.7% dorsally and 11.0 ± 4.0% ventrally), connectivity of dermal fat (98.5 ± 2.8% and 95.5 ± 6.8%), vascular density (26.5 ± 3.3% and 22.7 ± 2.3%). Absence of large differences in measured characteristics between particular body regions indicates that the thermal windows are determined mainly by the pelage characteristics.

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“…); an observation also made by Bennett et al (2006). The higher annual rainfall allows burrowing for most of the year (Thomas et al 2012) as it makes the soil workable (Scantlebury et al 2006) and reduces the energetic cost of digging (Lovegrove 1989;Zelová et al 2011;Okrouhlík et al 2015). High rainfall also ensures reliable food resources for most of the year (Bennett 1988).…”

Section: Ecology and Distributionmentioning

confidence: 99%

“…The larger relative testicular masses in this species are restricted to lower elevations and in lower rainfall (arid) areas. As such, variation in this reproductive trait may be linked to moisture -a factor which influences the energetic cost of digging and therefore mate searching (Lovegrove 1989;Zelová et al 2011;Okrouhlík et al 2015). In drier areas, mate searching may be more difficult and energetically expensive.…”

Section: Reproduction and Ecologymentioning

confidence: 99%

Distributional range, ecology, and mating system of the Cape mole-rat (Georychus capensis) family Bathyergidae

2017

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1Distributional range, ecology and mating system of the Cape mole-rat, Georychus capensis family Bathyergidae J. H. Visser, N. C. Bennett and B. Jansen van Vuuren AbstractInterpopulation variation in life-history patterns are influenced by intrinsic and extrinsic factors. Life-history patterns have been intensely studied in the eusocial African bathyergid species, largely neglecting the solitary species. Of these solitary genera, the Cape mole-rat, Georychus capensis (Pallas 1778), is endemic to South Africa with a disjunct distribution across its range. Knowledge regarding this species is rudimentary and therefore this study aimed to investigate the current distribution of the species with particular attention to common ecological variables, differences in body size between localities and sexes, as well as its reproduction and mating system. Georychus is a habitat specialist restricted to specific ecological areas. A lack of sexual size dimorphism and correlation between male testis size and the number of females in the population, suggests a polygynous mating system, facilitated by the spatial distribution of the sexes. A positive relationship between male testes size and the percentage of females in populations sampled suggests that larger sperm reserves (i.e., larger testes) are required in populations with a higher percentage of females. In addition, mating variables (testicular size and litter size) are linked to ecological factors (elevation, aridity, soil-and vegetation type) which could impact mate searching, mating success and food resources.

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Surprisingly low risk of overheating during digging in two subterranean rodents

Cited by 21 publications

References 46 publications

Thermoregulation in endotherms: physiological principles and ecological consequences

Thermoregulation in endotherms: physiological principles and ecological consequences

Functional histology of the skin in the subterranean African giant mole-rat: thermal windows are determined solely by pelage characteristics

Distributional range, ecology, and mating system of the Cape mole-rat (Georychus capensis) family Bathyergidae

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