1College of Medicine, University of Kentucky, 2College of Health Sciences, University of Kentucky, 3Department of Surgery, Saint Louis University School of Medicine, 4Department of Anatomy and Neurobiology, University of Kentucky College of Medicine
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Primate infants, unlike many mammals, are not fully prepared for locomotor independence at birth. Consequently, newborn primates differ in size, shape, and body composition (i.e. muscle mass) from adults (i.e. an infant macaque hand has nearly twice the relative muscle mass of an adult). As an infant gains locomotor independence, body segments grow disproportionately in mass (i.e. the arm increases in mass, while the hand decreases). Although ontogenetic variation in body mass is well understood in quadrupedal primates, relatively little is known about the ontogeny of body composition changes in platyrrhines. Platyrrhines with prehensile tails are unique among anthropoids because these tails serve as a fifth limb capable of grasping arboreal substrates.
Here we examine the potential for using CT data to collect ontogenetic body composition data for an age and sex varied sample of Lagothrix lagothrica (n=11). Mimics 14.1 was used to establish contrast thresholds for individual tissues (i.e. bone, muscle, adipose, integument). Relative tissue volmes were calculated for the arm, forearm, hand and tail with respect to total tissue volume. Results are congruent with previous mass-based body composition studies employing a traditional dissection-based approach and identify ontogenetic trends similar to those observed for quadrupedal cercopithecoids (i.e. arm, forearm, and tail muscle volume increases from infant to juvenile to adult; bone exhibits minimal ontogenetic variation). This study confirms that the use of CT data is a reliable and non-invasive method for collecting body composition data and that despite locomotor differences, the ontogenetic development of Lagothrix lagothrica parallels quadrupedal anthropoids.