Coloration affects heating and cooling in three color morphs of the Australian bluetongue lizard,Tiliqua scincoides |
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| Affiliation: | 1. School of BioSciences, The University of Melbourne, Australia;2. Division of Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australia;1. UMR 7179 Centre National de la Recherche Scientifique, Muséum National d׳Histoire Naturelle, 1 avenue du Petit Château, 91800 Brunoy, France;2. PG Consulting, 13 Villa Bellevue, 91440 Bures sur Yvette, France;3. Institut National de la Recherche Agronomique, Département Alimentation Humaine, Domaine de Vilvert, bât. 230, Nurélice UR 909, 78352 Jouy-en-Josas, France;1. School of Anatomy, Physiology and Human Biology M309, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;2. UWA Institute of Agriculture (Animal Production) M085, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;1. Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, ACT, Australia;2. Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia;1. Marian University College of Osteopathic Medicine, Indianapolis, IN, USA;2. Ohio Musculoskeletal and Neurologic Institute & Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, Athens, OH, USA;3. Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA, USA |
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| Abstract: | The color-mediated thermoregulation hypothesis predicts that dark body color (low reflectance) allows organisms to gain heat more efficiently than does pale coloration (high reflectance). This prediction is intuitive and widely assumed to be true, but has poor empirical support. We used rare, captive-bred, mutant melanistic, albino and wild-type Australian bluetongue lizards, Tiliqua scincoides to measure the effects of skin reflectance on the heating and cooling rates. We measured heating under an artificial radiant heat source and cooling rates in an ice-cooled box using live lizards in a room with still air. The effect of skin reflectance on heat transfer was clear, despite the substantial influence of body size. Melanistic T. scincoides showed low reflectance and gained heat faster than highly reflective albinos. Melanistic lizards also lost heat faster than albinos. Wild-type lizards were intermediate in reflectance, gained heat at rates indistinguishable from melanistic lizards, and lost heat at rates indistinguishable from albino lizards. This study system allowed us to control for variables that were confounded in other studies and may explain the inconsistent support for the color-mediated thermoregulation hypothesis. Our results provide clear evidence that skin reflectance influences the rate of heating and cooling in ectotherms. |
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| Keywords: | Albinism Melanism Reflectance Reptiles Color-mediated thermoregulation Thermal melanism |
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