AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 4 744-R751, Copyright © 1989 by American Physiological Society

ARTICLES

Nonshivering thermogenesis and adaptation to fasting in king penguin chicks

C. Duchamp, H. Barre, D. Delage, J. L. Rouanet, F. Cohen-Adad and Y. Minaire
Laboratoire de Thermoregulation et Energetique de l'Exercice, Centre National de la Recherche Scientifique, Faculte de Medecine, Lyon-Nord, France.

The ability to develop nonshivering thermogenesis (NST) and the effect of fasting on thermogenic response to cold were studied in winter-acclimatized king penguin chicks. Metabolic rate (MR) and integrated electrical muscle activity were measured at different ambient temperatures. In cold-acclimatized (5 degrees C) fed chicks, shivering threshold temperature (STT) was 9.4 degrees C lower than lower critical temperature (LCT), indicating that NST (0.7 W/kg) occurs at moderate cold, whereas in control chicks fed and reared at 25 degrees C for 3 wk, LCT and STT were similar. Chicks reared in the cold and fasting for 3 wk or 4-5 mo (natural winter fast) developed an NST of 0.8 and 2.4 W/kg, respectively, despite the fast. In fasting chicks, the intercept of the metabolic curve with the abscissa at zero MR was far below body temperature, contrasting with the classic model for heat loss. Their low LCT indicates the capacity of a large reduction in convective conductance characteristic of diving animals and allows energy sparing in moderate cold. Below LCT, conductance reincreases progressively, leading to a steeper than expected slope of the metabolic curve and allowing preservation of a threshold temperature in the shell. These results show for the first time in a wild young bird the development of NST after cold acclimatization. Further, at the temperature of cold acclimatization, an energy-sparing mechanism is shown in response to long-term fast adaptation.

This article has been cited by other articles:

				B. Rey, L. G. Halsey, V. Dolmazon, J.-L. Rouanet, D. Roussel, Y. Handrich, P. J. Butler, and C. Duchamp Long-term fasting decreases mitochondrial avian UCP-mediated oxygen consumption in hypometabolic king penguins Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2008; 295(1): R92 - R100. [Abstract] [Full Text] [PDF]

				M. Jastroch, S. Wuertz, W. Kloas, and M. Klingenspor Uncoupling protein 1 in fish uncovers an ancient evolutionary history of mammalian nonshivering thermogenesis Physiol Genomics, July 14, 2005; 22(2): 150 - 156. [Abstract] [Full Text] [PDF]

				A. A. Romanovsky Do fever and anapyrexia exist? Analysis of set point-based definitions Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2004; 287(4): R992 - R995. [Abstract] [Full Text] [PDF]

				F. Marmonier, C. Duchamp, F. Cohen-Adad, T. P. D. Eldershaw, and H. Barre Hormonal control of thermogenesis in perfused muscle of Muscovy ducklings Am J Physiol Regulatory Integrative Comp Physiol, November 1, 1997; 273(5): R1638 - R1648. [Abstract] [Full Text] [PDF]