Partitioning respiratory and cutaneous water loss in the naked mole-rat Heterocephalus glaber

LUNA F; SUMBERA R; OKROUHLÍK J

Workshop; 5to Workshop de Fisiología Ecológica y del Comportamiento; 2023

Terrestrial life is challenging forendotherms, due to the need to maintain an adequate water balance. One of themost important pathways by which water is lost is through evaporation. Totalevaporative water loss (TEWL) can be partitioned into cutaneous (CEWL) orrespiratory (REWL) evaporation. Mammalian species that constantly live inunderground burrows characterized by high relative humidity (RH) and relativelyhigh Tas, may face achallenge for thermoregulation considering the magnitude of evaporation. Amongsubterranean mammals, the naked mole-rat Heterocephalus glaberrepresents a unique opportunity to assess whether lack ofinsulating fur and fat has an effect on TEWL, and particularly whether TEWLrelies primarily on cutaneous pathways. CEWL is assumed to be the major pathwayof evaporative water loss in the naked mole-rat at high Tas, and the proportionof evaporative cooling is more important than non-evaporative components inheat loss. CEWL increases _41 % when individualsmove to high Tas (e.g. from 32°C to 37.5°C), without an increase in REWL or metabolicrate. CEWL represents _60% of TEWL at 37.5°C,indicating an onset of physiological mechanisms serving to increase TEWL basedon cutaneous evaporation. Importantly, TEWL isnot as high as it has beenproposed, being allometrically comparable to other subterranean species. Theapparent thermal tolerance to high Tas and the low energy expenditure of evaporative coolingdue to the use of cutaneous pathways is probably important for the survival inthe arid environment in which naked mole-rats live.