Microstructural Variations in the Bone of Pygoscelis antarctica (Aves, Sphenisciformes) During the Postnatal Ontogeny

Abstract

We analyzed how the bone microstructure of the Antarctic penguin Pygoscelis antarcticachanges during growth. To explore this, 52 thin sections from the appendicular and axialskeleton of several individuals representing different life stages were analyzed. Our resultsshow that, in the youngest chicks, bones have thin walls, are more vascularized, and haveabundant trabecular tissue surrounding a large internal cavity. As the chicks grow, bone tissuegradually thickens, trabeculae expand, and the skeleton becomes progressively denser.In the juvenile, the bones begin to show stronger internal organization, including the firstsigns of inner circumferential layers and more intense bone remodeling. Adult bonesdisplay fully developed structural layers, dense lamellar tissue, and extensive secondaryremodeling, although the size of the internal cavity varies among skeletal elements. Comparisonswith previous results for the larger king penguin Aptenodytes patagonicus showthat P. antarctica exhibits an earlier reduction in the internal cavity and greater compactionin the forelimbs. These differences likely reflect its shorter period of parental care and theearlier onset of swimming behavior.