The microenvironment of naked mole-rat burrows in East Africa

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 degrees C), mostly within the species' thermoneutral zone, demonstrating their ability to maintain homoiothermy even under wide fluctuations of burrow temperature (24.6-48.8 degrees 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 CO2 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.