The microenvironment of naked mole‐rat burrows in East Africa

Abstract

Naked mole-rats (Heterocephalus glaber) can be extremely long-lived and are resistant to cancer. Hence, they have been proposed as a model organism for delayed ageing. Adaptation to a constant hypoxic and hypercapnic environment has been suggested as reason for their apparent ability to tolerate oxidative stress. Nevertheless, little is known about the natural habitat to which the species evolved. Naked mole-rat burrow environments were assessed in Ethiopia and Kenya. Despite reported thermolability of naked mole-rats, skin temperature upon capture varied (23.7-35.4°C), mostly within the species' thermoneutral zone, demonstrating their ability to maintain homoiothermy even under wide fluctuations of burrow temperature (24.6-48.8°C) and humidity (31.2%-92.8%), which are far greater than previously reported. Burrow temperature regularly alternates during the daytime and night-time, driving convective currents that circulate air in the tunnels. Consequently, concentrations of CO 2 and O 2 in burrows only slightly deviated from surface atmosphere. This contradicts the assumption of constant hypoxia/hypercapnia in subterranean burrows. In addition to diffusion, animal movement and occasional wind-driven ventilation, our data support the temperature-driven convective model of circulation. The naked mole-rat burrow is a relatively normoxic subterranean microenvironment with considerable fluctuations in temperature and humidity. La temp erature des terriers alterne r eguli erement entre le jour et la nuit, entraînant

Mild depolarization of the inner mitochondrial membrane is a crucial component of an anti-aging program

“…and T.B.H.) and their coworkers recently reported normal [O 2 ] in natural NMR burrows in Africa (52).…”

The hypoxia tolerance of eight related African mole‐rat species rivals that of naked mole‐rats, despite divergent ventilatory and metabolic strategies in severe hypoxia

“…In social species where numerous animals live within the confined space of the nest, and there is poor gas diffusion through the surrounding soils, the conditions faced (intermittent acute (or chronic) hypoxic and hypercarbic conditions) can be severe. However, reports of the composition of gases, and thus the severity of hypoxia and hypercarbia, in burrows of fossorial species vary greatly, from 20 to 6 kPa O 2 and 1 to 9.5 kPa CO 2 . The timing and location of burrow measurements presumably contribute to this variability, as well as other factors, such as burrow structure, soil type, number of occupants and degree of fossoriality …”

“…However, reports of the composition of gases, and thus the severity of hypoxia and hypercarbia, in burrows of fossorial species vary greatly, from 20 to 6 kPa O 2 and 1 to 9.5 kPa CO 2 . 1,[4][5][6][7][8][9] The timing and location of burrow measurements presumably contribute to this variability, as well as other factors, such as burrow structure, soil type, number of occupants and degree of fossoriality. 1,10 The response to hypoxia in mammals may consist of increases in ventilation (to match O 2 supply to metabolic demand; the hypoxia ventilatory response), decreases in metabolic rate (to match metabolic demand to O 2 supply; the hypoxic metabolic response) or a combination of the two.…”

Independent evolution of pain insensitivity in African mole-rats: origins and mechanisms

“…Indeed, in the brain, naked mole-rats appear to have smaller acid-induced currents and decreased acidinduced cell death, suggesting a further protective mechanism (Husson and Smith 2018). It was recently reported that carbon dioxide levels are elevated in naked mole-rat burrows (Holtze et al 2018), but that the level reached is less than that generally associated with hypercapnia-induced changes in respiration rate. However, the levels of carbon dioxide reached in sleeping chambers where the majority of the colony sleep together remain to be measured.…”