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Evaporative water loss in subterranean rodents from two continents: A Bathyergidae - Ctenomyidae comparison
Workshop; 3er Workshop "Ecofisiología: Interacciones de los organismos con su ambiente"; 2017
Salt-water balance is important for life. It is challenging especially for those organisms that require special water-regulatory mechanisms because of life in a specific habitat, or their behavior and/or physiology. In endotherms, a significant way of water loss is evaporation. Evaporative water loss (EWL) is inevitable, but individuals can regulate it in some aspects and use it for cooling, as exceeding heat is dissipated by evaporating body water. Interesting mammals to analyze EWL are those with subterranean habitats, because one of the most important challenges for life in underground environment is the need to dig new burrows through a dense substrate in an almost water saturated atmosphere. The heat produced during digging in such environment could cause overheating in individuals, especially at ambient temperatures (Ta) within and above the thermoneutral zone (TNZ). The aim of this study was to evaluate the effect of Ta on EWL and energy metabolism of subterranean species of different phylogenetically non-related rodent lineages: African mole-rats (Bathyergidae) and tuco-tucos (Ctenomiydae). We evaluate the EWL of two bathyergids; the solitary Heliophobius argenteocinereus, and the social Fukomys mechowii, and two solitary ctenomyids Ctenomys talarum and C. australis. Individuals of all species follow typical endotherm pattern, maintaining relatively stable EWL below and within TNZ and increasing evaporation above TNZ. Particularly, C. australis, shows high EWL in the range of Tas measured (15°C to 38°C). At high Ta (38°C), both F. mechowii and C. australis become hyperthermic (Tb of 39.1±0.4 °C and 39.9±0.8 °C, respectively). We relate ecological patterns (habitats? differences, etc.) to the underlying physiological mechanisms aiming to understand the evaporative water and heat loss in subterranean rodents. Finally, by comparing unrelated species of subterranean mammals, we give insights into the factors that influence the broad scale pattern of EWL in these mammals.