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Am J Physiol Regul Integr Comp Physiol 285: R850-R861, 2003. First published June 5, 2003; doi:10.1152/ajpregu.00105.2003
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APPETITE, OBESITY AND METABOLISM

Metabolic fate of yolk fatty acids in the developing king penguin embryo

René Groscolas,1 Françoise Fréchard,1 Frédéric Decrock,1 and Brian K. Speake2

1Centre d'Ecologie et Physiologie Energétiques, Centre National de la Recherche Scientifique, 67087 Strasbourg, France; and 2Avian Science Research Center, Scottish Agricultural College, Ayr KA6 5HW, United Kingdom

Submitted 3 March 2003 ; accepted in final form 30 May 2003

This study examines the metabolic fate of total and individual yolk fatty acids (FA) during the embryonic development of the king penguin, a seabird characterized by prolonged incubation (53 days) and hatching (3 days) periods, and a high n-3/n-6 polyunsaturated FA ratio in the egg. Of the ~15 g of total FA initially present in the egg lipid, 87% was transferred to the embryo by the time of hatching, the remaining 13% being present in the internalized yolk sac of the chick. During the whole incubation, 83% of the transferred FA was oxidized for energy, with only 17% incorporated into embryo lipids. Prehatching (days 0-49), the fat stores (triacylglycerol) accounted for 58% of the total FA incorporated into embryo lipid. During hatching (days 49-53), 40% of the FA of the fat stores was mobilized, the mobilization of individual FA being nonselective. At hatch, 53% of the arachidonic acid (20:4n-6) of the initial yolk had been incorporated into embryo lipid compared with only 15% of the total FA and 17-24% of the various n-3 polyunsaturated FA. Similarly, only 32% of the yolk's initial content of 20:4n-6 was oxidized for energy during development compared with 72% of the total FA and 58-66% of the n-3 polyunsaturated FA. The high partitioning of yolk FA toward oxidization and the intense mobilization of fat store FA during hatching most likely reflect the high energy cost of the long incubation and hatching periods of the king penguin. The preferential partitioning of 20:4n-6 into the structural lipid of the embryo in the face of its low content in the yolk may reflect the important roles of this FA in tissue function.

bird development; fatty acid transfer; fatty acid oxidation; n-3 polyunsaturated fatty acid; n-6 polyunsaturated fatty acid


Address for reprint requests and other correspondence: R. Groscolas, Centre d'Ecologie et Physiologie Energétiques, CNRS, 23 rue Becquerel, 67087 Strasbourg, France (E-mail: rene.groscolas{at}c-strasbourg.fr).






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