Thermoconformity strategy in the freshwater turtle Hydromedusa tectifera (Testudines,Chelidae) in its southern distribution area |
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Institution: | 1. Centro de Zoología Aplicada, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Rondeau 798, Córdoba 5000, Argentina;2. Instituto de Diversidad y Ecología Animal (IDEA), CONICET-UNC, Vélez Sarsfield 299, Córdoba 5000, Argentina;1. Graduate School of Bioresource and Bioenvironmental Science, Division for Experimental Natural Science, Faculty of Arts and Science, Kyushu University, Fukuoka 819-0395, Japan;2. Laboratory of Regulation in Metabolism and Behavior, Graduate School of Bioresource and Bioenvironmental Science, Kyushu University, Fukuoka 812-8581, Japan;1. School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand;2. Research Office, The Open Polytechnic of New Zealand, Private Bag 31914, Lower Hutt 5040, New Zealand;1. Department of Mathematics and Statistics, Sam Houston State University, Huntsville, TX, 77341, United States;2. Department of Biological Sciences, Sam Houston State University, Huntsville, TX, 77341, United States |
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Abstract: | Ectotherm species are not capable of generating metabolic heat; therefore, they present different strategies for regulating their body temperatures, ranging from a precise degree of thermoregulation to a passive thermoconformity with ambient temperatures. In reptiles, aerial basking is the most common mechanism for gaining heat. However, among aquatic reptiles, such as freshwater turtles, aquatic basking is also frequent. Hydromedusa tectifera is a turtle of exclusively aquatic and nocturnal habits widely distributed in South America. We studied the relationship between body temperature (Tb) of H. tectifera and its habitat, and explored the effects of sex, life stage and body size and mass on Tb. Fieldwork was conducted in two streams of a mountain area of central Argentina. We recorded cloacal temperature, size and mass of 84 turtles. We also determined individuals’ sex and life stage (adult/juvenile). Regarding ambient temperatures, we measured water temperature on the surface (Tsurf) and at depth of turtle capture (Tdepth) and air temperature. Mean Tb was 18.58 °C (Min = 10.20 °C; Max = 25.70 °C). Tsurf and Tdepth were highly correlated. Multi-model analysis using Akaike criterion indicated that Tb was strongly associated with water temperature, whereas air temperature and body size and mass did not show a significant effect. There was also no effect of turtle sex or life stage on Tb. Our results indicate that H. tectifera is a thermoconformer and eurythermal species. A nocturnal pattern of activity and a fully aquatic lifestyle are suggested as determinant factors. |
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Keywords: | Thermoregulation Body temperature Freshwater turtles Chaco region Argentina |
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