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Three-dimensional kinematic analysis of the pectoral girdle during upside-down locomotion of two-toed sloths (Choloepus didactylus, Linné 1758).

Nyakatura JA, Fischer MS - Front. Zool. (2010)

Bottom Line: Reduction of the relative length of the scapula alters its displacing effect on limb excursions.The morphological characteristics of the scapula and the SCA allow maximal mobility of the forelimb to facilitate effective locomotion within a discontinuous habitat.These evolutionary changes associated with the adoption of the suspensory posture emphasized humeral influence on forelimb motion, but allowed the retention of the plesiomorphic 3D kinematic pattern.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität, Erbertstrasse 1, 07743 Jena, Germany. john.nyakatura@uni-jena.de.

ABSTRACT

Background: Theria (marsupials and placental mammals) are characterized by a highly mobile pectoral girdle in which the scapula has been shown to be an important propulsive element during locomotion. Shoulder function and kinematics are highly conservative during locomotion within quadrupedal therian mammals. In order to gain insight into the functional morphology and evolution of the pectoral girdle of the two-toed sloth we here analyze the anatomy and the three-dimensional (3D) pattern of shoulder kinematics during quadrupedal suspensory ('upside-down') locomotion.

Methods: We use scientific rotoscoping, a new, non-invasive, markerless approach for x-ray reconstruction of moving morphology (XROMM), to quantify in vivo the 3D movements of all constituent skeletal elements of the shoulder girdle. Additionally we use histologic staining to analyze the configuration of the sterno-clavicular articulation (SCA).

Results: Despite the inverse orientation of the body towards gravity, sloths display a 3D kinematic pattern and an orientation of the scapula relative to the thorax similar to pronograde claviculate mammalian species that differs from that of aclaviculate as well as brachiating mammals. Reduction of the relative length of the scapula alters its displacing effect on limb excursions. The configuration of the SCA maximizes mobility at this joint and demonstrates a tensile loading regime between thorax and limbs.

Conclusions: The morphological characteristics of the scapula and the SCA allow maximal mobility of the forelimb to facilitate effective locomotion within a discontinuous habitat. These evolutionary changes associated with the adoption of the suspensory posture emphasized humeral influence on forelimb motion, but allowed the retention of the plesiomorphic 3D kinematic pattern.

No MeSH data available.


Related in: MedlinePlus

Anatomical coordinate systems and zero-positions of rotations are used to quantify three-dimensional kinematics of the pectoral girdle. The anatomical coordinate systems were placed in the center of rotation (c.o.r.) of the proximally adjacent joint (in case of 1st thoracic vertebra into the center of the vertebral body; in case of scapula we approximated the instantaneous c.o.r. at the vertebral border of the scapula at the extension of the spina scapulae). X-axes (red) were set to represent the long axis of elements. Z-axes (blue) were oriented to represent the most distinct motion of the bone of interest. Y-axes (green) were orthogonal to the other two axes. For zero-points of rotations the anatomical axes were aligned according to the global coordinate system (unnatural pose). Motions of hierarchically higher elements have displacing effect for all lower ranked elements, i.e., motions of humerus are reported relative to scapula, scapular and clavicular motion relative to 1st thoracic vertebra, 1st thoracic vertebra motion relative to global reference.
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Figure 2: Anatomical coordinate systems and zero-positions of rotations are used to quantify three-dimensional kinematics of the pectoral girdle. The anatomical coordinate systems were placed in the center of rotation (c.o.r.) of the proximally adjacent joint (in case of 1st thoracic vertebra into the center of the vertebral body; in case of scapula we approximated the instantaneous c.o.r. at the vertebral border of the scapula at the extension of the spina scapulae). X-axes (red) were set to represent the long axis of elements. Z-axes (blue) were oriented to represent the most distinct motion of the bone of interest. Y-axes (green) were orthogonal to the other two axes. For zero-points of rotations the anatomical axes were aligned according to the global coordinate system (unnatural pose). Motions of hierarchically higher elements have displacing effect for all lower ranked elements, i.e., motions of humerus are reported relative to scapula, scapular and clavicular motion relative to 1st thoracic vertebra, 1st thoracic vertebra motion relative to global reference.

Mentions: Motions of the modeled skeletal elements forming the digital marionette are reported relative to hierarchically higher ordered elements (Table 3). Right handed anatomical coordinate systems were implemented at the center of rotation of each element (Fig. 2). Translations were set to zero at the instant of touch down.


Three-dimensional kinematic analysis of the pectoral girdle during upside-down locomotion of two-toed sloths (Choloepus didactylus, Linné 1758).

Nyakatura JA, Fischer MS - Front. Zool. (2010)

Anatomical coordinate systems and zero-positions of rotations are used to quantify three-dimensional kinematics of the pectoral girdle. The anatomical coordinate systems were placed in the center of rotation (c.o.r.) of the proximally adjacent joint (in case of 1st thoracic vertebra into the center of the vertebral body; in case of scapula we approximated the instantaneous c.o.r. at the vertebral border of the scapula at the extension of the spina scapulae). X-axes (red) were set to represent the long axis of elements. Z-axes (blue) were oriented to represent the most distinct motion of the bone of interest. Y-axes (green) were orthogonal to the other two axes. For zero-points of rotations the anatomical axes were aligned according to the global coordinate system (unnatural pose). Motions of hierarchically higher elements have displacing effect for all lower ranked elements, i.e., motions of humerus are reported relative to scapula, scapular and clavicular motion relative to 1st thoracic vertebra, 1st thoracic vertebra motion relative to global reference.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2908604&req=5

Figure 2: Anatomical coordinate systems and zero-positions of rotations are used to quantify three-dimensional kinematics of the pectoral girdle. The anatomical coordinate systems were placed in the center of rotation (c.o.r.) of the proximally adjacent joint (in case of 1st thoracic vertebra into the center of the vertebral body; in case of scapula we approximated the instantaneous c.o.r. at the vertebral border of the scapula at the extension of the spina scapulae). X-axes (red) were set to represent the long axis of elements. Z-axes (blue) were oriented to represent the most distinct motion of the bone of interest. Y-axes (green) were orthogonal to the other two axes. For zero-points of rotations the anatomical axes were aligned according to the global coordinate system (unnatural pose). Motions of hierarchically higher elements have displacing effect for all lower ranked elements, i.e., motions of humerus are reported relative to scapula, scapular and clavicular motion relative to 1st thoracic vertebra, 1st thoracic vertebra motion relative to global reference.
Mentions: Motions of the modeled skeletal elements forming the digital marionette are reported relative to hierarchically higher ordered elements (Table 3). Right handed anatomical coordinate systems were implemented at the center of rotation of each element (Fig. 2). Translations were set to zero at the instant of touch down.

Bottom Line: Reduction of the relative length of the scapula alters its displacing effect on limb excursions.The morphological characteristics of the scapula and the SCA allow maximal mobility of the forelimb to facilitate effective locomotion within a discontinuous habitat.These evolutionary changes associated with the adoption of the suspensory posture emphasized humeral influence on forelimb motion, but allowed the retention of the plesiomorphic 3D kinematic pattern.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität, Erbertstrasse 1, 07743 Jena, Germany. john.nyakatura@uni-jena.de.

ABSTRACT

Background: Theria (marsupials and placental mammals) are characterized by a highly mobile pectoral girdle in which the scapula has been shown to be an important propulsive element during locomotion. Shoulder function and kinematics are highly conservative during locomotion within quadrupedal therian mammals. In order to gain insight into the functional morphology and evolution of the pectoral girdle of the two-toed sloth we here analyze the anatomy and the three-dimensional (3D) pattern of shoulder kinematics during quadrupedal suspensory ('upside-down') locomotion.

Methods: We use scientific rotoscoping, a new, non-invasive, markerless approach for x-ray reconstruction of moving morphology (XROMM), to quantify in vivo the 3D movements of all constituent skeletal elements of the shoulder girdle. Additionally we use histologic staining to analyze the configuration of the sterno-clavicular articulation (SCA).

Results: Despite the inverse orientation of the body towards gravity, sloths display a 3D kinematic pattern and an orientation of the scapula relative to the thorax similar to pronograde claviculate mammalian species that differs from that of aclaviculate as well as brachiating mammals. Reduction of the relative length of the scapula alters its displacing effect on limb excursions. The configuration of the SCA maximizes mobility at this joint and demonstrates a tensile loading regime between thorax and limbs.

Conclusions: The morphological characteristics of the scapula and the SCA allow maximal mobility of the forelimb to facilitate effective locomotion within a discontinuous habitat. These evolutionary changes associated with the adoption of the suspensory posture emphasized humeral influence on forelimb motion, but allowed the retention of the plesiomorphic 3D kinematic pattern.

No MeSH data available.


Related in: MedlinePlus