Ontogenetic scaling of foot musculoskeletal anatomy in elephants

Abstract

This study quantifies the shape change in elephant manus and pes anatomy with increasing body mass, using computed tomographic scanning. Most manus and pes bones, and manus tendons, maintain their shape, or become more gracile, through ontogeny. Contrary to this, tendons of the pes become significantly more robust, suggesting functional adaptation to increasingly high loads. Ankle tendon cross-sectional area (CSA) scales the highest in the long digital extensor, proportional to body mass 1.08G0.21 , significantly greater than the highest-scaling wrist tendon (extensor carpi ulnaris, body mass 0.69G0.09 ). These patterns of shape change relate to the marked anatomical differences between the pillar-like manus and tripod-like pes, consistent with differences in fore-and hindlimb locomotor function. The cartilaginous predigits (prepollux and prehallux) of the manus and pes also become relatively more robust through ontogeny, and their pattern of shape change does not resemble that seen in any of the 10 metacarpals and metatarsals. Their CSAs scale above isometry proportional to body mass 0.73G0.09 and body mass 0.82G0.07 respectively. We infer a supportive function for these structures, preventing collapse of the foot pad during locomotion.

Ontogenetic scaling of locomotor kinetics and kinematics of the ostrich (Struthio camelus)

“…jack rabbit (Carrier, 1983); gull (Carrier and Leon, 1990); muskox (Heinrich et al, 1999); emu (Main and Biewener, 2007)] than those with negative allometric scaling [e.g. lizard (Irschick and Jayne, 2000); elephant (Miller et al, 2008)]. Positive allometry may relate to the pressure to grow quickly and to the required athleticism of the species during ontogeny and as an adult or to the species-specific starting point in terms of development and limits of growth of the musculoskeletal system.…”

“…As ostriches hatch at masses of approximately 600g and must grow quickly to achieve adult stature, the growth rate in this species is rapid, increasing in mass by a factor of 100 within six months and showing a 10-fold increase in height during the same time span. Ontogenetic studies in other species have identified deviations from isometric scaling, reporting evidence of both positive (Carrier, 1983;Carrier and Leon, 1990;Heinrich et al, 1999;Main and Biewener, 2007) and negative (Irschick and Jayne, 2000;Miller et al, 2008) allometry of bone length of specific bones in a variety of species. However, none of the species previously studied through growth show the large and rapid increase in body size observed in the ostrich, or the level of athletic performance of the fastest living biped, which in itself has implications for stress in the musculoskeletal system.…”

Statistical parametric mapping of the regional distribution and ontogenetic scaling of foot pressures during walking in Asian elephants (Elephas maximus)

“…prepollex and prehallux or 'predigits') connect the proximal carpal/tarsal bones with the substrate. These structures should direct some unknown portion of the ground reaction force (GRF) directly proximally rather than through the distal phalanges, as in truly plantigrade animals (D'Aout et al, 2010;Michilsens et al, 2009;Miller et al, 2008).…”

Macroanatomy of the Bones of Thoracic Limb of an Asian Elephant (Elephas maximus)

“…Digits I and V were vertical and digit II, III and IV were horizontal. The functional consequence of the shape of the manus was that digits II, III and IV act like three supports of a tripod, in contrast to the more unified column of the manus (Miller et al, 2008). This was disagreement in cattle (Sisson et al) and disagreement in horse (Sisson et al) where, only fully developed two digits (III and IV) and one digit was found in forelimb respectively.…”