Papers by Heather Paxton
The Journal of experimental biology, 2008
As the largest extant terrestrial animals, elephants do not trot or gallop but can move smoothly ... more As the largest extant terrestrial animals, elephants do not trot or gallop but can move smoothly to faster speeds without markedly changing their kinematics, yet with a shift from vaulting to bouncing kinetics. To understand this unusual mechanism, we quantified the forelimb and hindlimb motions of eight Asian elephants (Elephas maximus) and seven African elephants (Loxodonta africana). We used 240 Hz motion analysis (tracking 10 joint markers) to measure the flexion/extension angles and angular velocities of the limb segments and joints for 288 strides across an eightfold range of speeds (0.6-4.9 m s(-1)) and a sevenfold range of body mass (521-3684 kg). We show that the columnar limb orientation that elephants supposedly exemplify is an oversimplification--few segments or joints are extremely vertical during weight support (especially at faster speeds), and joint flexion during the swing phase is considerable. The 'inflexible' ankle is shown to have potentially spring-li...
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Journal of Anatomy, 2010
Intensive artificial selection has led to the production of the modern broiler chicken, which ove... more Intensive artificial selection has led to the production of the modern broiler chicken, which over the last few decades has undergone a dramatic increase in growth rate and noticeable changes in body conformation. Unfortunately, this has been associated with musculoskeletal abnormalities which have altered the walking ability of these birds, raising obvious welfare concerns, as well as causing economic losses. Here we present a comparative study of ancestral and derived muscle anatomy in chickens to begin to tease apart how evolutionary alterations of muscle form in chickens have influenced their locomotor function and perhaps contributed to lameness. We measured the muscle architectural properties of the right pelvic limb in 50 birds, including the Giant Junglefowl, a commercial strain broiler and four pureline commercial broiler breeder lines (from which the broiler populations are derived) to identify which features of the broiler’s architectural design have diverged the most from the ancestral condition. We report a decline in pelvic limb muscle mass in the commercial line birds that may compromise their locomotor abilities because they carry a larger body mass. This greater demand on the pelvic limb muscles has mostly led to changes in support at the hip joint, revealing significantly larger abductors and additionally much larger medial rotators in the broiler population. Differences were seen within the commercial line bird populations, which are likely attributed to different selection pressures and may reflect differences in the walking ability of these birds. In addition, Junglefowl seem to have both greater force-generating capabilities and longer, presumably faster contracting muscles, indicative of superior musculoskeletal/locomotor function. We have provided baseline data for generating hypotheses to investigate in greater depth the specific biomechanical constraints that compromise the modern broiler’s walking ability and propose that these factors should be considered in the selection for musculoskeletal health in the chickens of the future. Our new anatomical data for a wide range of domestic and wild-type chickens is useful in a comparative context and for deeper functional analysis including computer modelling/simulation of limb mechanics.
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Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2009
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Journal of Experimental Biology, 2008
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Journal of Fish Biology, 2006
Regional variation in properties of vertebral bone from brown Salmo trutta and rainbow trout Onco... more Regional variation in properties of vertebral bone from brown Salmo trutta and rainbow trout Oncorhychus mykiss were explored by using microhardness tests. Statistically-significant positive correlations were identified between the microhardness of bone and its mineral content. In both brown and rainbow trout, the vertebrae from the caudal region were harder than those of the trunk region. There was a significant difference between the species; microhardness of bone from vertebrae of rainbow trout was greater than those from brown trout.
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Conference Presentations by Heather Paxton
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2009
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Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2008
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Papers by Heather Paxton
Conference Presentations by Heather Paxton