Journal of Experimental Biology
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Physiological plasticity allows organisms to respond to diverse conditions. However, can being too plastic actually be detrimental? Malagasy common tenrecs, Tenrec ecaudatus, have many plesiomorphic traits and may represent a basal placental mammal. We established a laboratory population of T. ecaudatus and found extreme plasticity in thermoregulation and metabolism, a novel hibernation form, variable annual timing, and remarkable growth and reproductive biology. For instance, tenrec body temperature (Tb) may approximate ambient temperature to as low as 12°C even when tenrecs are fully active. Conversely, tenrecs can hibernate with Tb of 28°C. During the active season, oxygen consumption may vary 25-fold with little or no change in Tb. During the austral winter, tenrecs are consistently torpid but the depth of torpor may vary. A righting assay revealed that Tbcontributes to but does not dictate activity status. Homeostatic processes are not always linked, e.g. a hibernating tenrec experienced a ∼34% decrease in heart rate while maintaining constant body temperature and oxygen consumption rates. Tenrec growth rates vary but young may grow ∼40-fold in the 5 weeks until weaning and may possess indeterminate growth as adults. Despite all of this profound plasticity, tenrecs are surprisingly intolerant of extremes in ambient temperature (34°C). We contend that while plasticity may confer numerous energetic advantages in consistently moderate environments, environmental extremes may have limited the success and distribution of plastic basal mammals.
Oxygen consumption; Thermoregulation; Variable body temperature
Treat, M. D.,
McKenna, A. J.,
Ronkon, C. F.,
Santamaria, J. F.,
Rubio, C. S.,
Lighton, J. R.,
van Breukelen, F.
Extreme Physiological Plasticity in a Hibernating Basoendothermic Mammal, Tenrec ecaudatus.
Journal of Experimental Biology, 221(20),
Available for download on Friday, October 18, 2019