title: Three African antelope species with varying water dependencies exhibit similar selective brain cooling.
abstract: The use of selective brain cooling, where warm arterial blood destined for the brain is cooled in the carotid rete via counter-current heat exchange when in close proximity to cooler venous blood, contributes to the conservation of body water. We simultaneously measured carotid blood and hypothalamic temperature in four gemsbok, five red hartebeest and six blue wildebeest to assess the extent to which these free-living animals, with varying water dependency, routinely rely on selective brain cooling. We investigated the hypothesis that innate differences in selective brain cooling exist in large, sympatric artiodactyls with varying water dependency. All three species used selective brain cooling, without any discernible differences in three selective brain cooling indices. GLMMs revealed no species differences in the threshold temperature for selective brain cooling (z = 0.79, P = 0.43), the magnitude (z = -0.51, P = 0.61), or the frequency of selective brain cooling use (z = -0.47, P = 0.64), after controlling for carotid blood temperature and black globe temperature. Comparison of anatomical attributes of the carotid retes of the three species revealed that the volume (F 2,9 = 5.54, P = 0.03) and height (F 2,9 = 5.43, P = 0.03) of the carotid rete, per kilogram body mass, were greater in the red hartebeest than in the blue wildebeest. Nevertheless, intraspecific variability in the magnitude, the frequency of use, and the threshold temperature for selective brain cooling exceeded any interspecific variability in the three indices of selective brain cooling. We conclude that the three species have similar underlying ability to make use of selective brain cooling in an environment with freely available water. It remains to be seen to what extent these three species would rely on selective brain cooling, as a water conservation mechanism, when challenged by aridity, a condition likely to become prevalent throughout much of southern Africa under future climate change scenarios.
authors.affiliation: School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa. strauwm@unisa.ac.za.|Department of Environmental Sciences, University of South Africa, Johannesburg, South Africa. strauwm@unisa.ac.za.
authors.forename: W Maartin
authors.initials: WM
authors.lastname: Strauss
authors.affiliation: School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.|School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Robyn S
authors.initials: RS
authors.lastname: Hetem
authors.affiliation: School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Duncan
authors.initials: D
authors.lastname: Mitchell
authors.affiliation: School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.|School of Anatomy, Physiology, and Human Biology, University of Western Australia, Perth, Australia.
authors.forename: Shane K
authors.initials: SK
authors.lastname: Maloney
authors.affiliation: School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Leith C R
authors.initials: LC
authors.lastname: Meyer
authors.affiliation: School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Andrea
authors.initials: A
authors.lastname: Fuller
mesh_terms: D000818:Animals; D000866:Antelopes / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology; D001833:Body Temperature Regulation / Q000502:physiology*; D001834:Body Water / Q000502:physiology; D001921:Brain / Q000502:physiology*; D002339:Carotid Arteries / Q000033:anatomy & histology / Q000502:physiology; D005260:Female; D013019:South Africa; D013045:Species Specificity
keywords: Artiodactyl; Climate change adaptation; Conservation physiology; Plasticity; Rostral epidural rete mirabile; Water conservation