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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.


Representative frames of instants of (A) touch down, (B) mid contact, (C) lift off, and (D) mid swing. X-ray image with bone model posed to match the x-ray shadow is shown for the dorso-ventral projection and the latero-lateral projection.
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Figure 5: Representative frames of instants of (A) touch down, (B) mid contact, (C) lift off, and (D) mid swing. X-ray image with bone model posed to match the x-ray shadow is shown for the dorso-ventral projection and the latero-lateral projection.

Mentions: Movements of the shoulder blade follow the morphology of the thorax and are confined by the clavicle (Fig. 5). The center of rotation of scapular protraction and retraction is positioned at the vertebral border of the scapula. We documented slight translations of the center of rotation in the second half of the contact phase (Fig. 4B), the most prominent being a caudal translation along the thoracic wall with a maximum of about 0.8 cm on average (Table 4). At the same time the center of rotation is translated laterally and ventrally.


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)

Representative frames of instants of (A) touch down, (B) mid contact, (C) lift off, and (D) mid swing. X-ray image with bone model posed to match the x-ray shadow is shown for the dorso-ventral projection and the latero-lateral projection.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Representative frames of instants of (A) touch down, (B) mid contact, (C) lift off, and (D) mid swing. X-ray image with bone model posed to match the x-ray shadow is shown for the dorso-ventral projection and the latero-lateral projection.
Mentions: Movements of the shoulder blade follow the morphology of the thorax and are confined by the clavicle (Fig. 5). The center of rotation of scapular protraction and retraction is positioned at the vertebral border of the scapula. We documented slight translations of the center of rotation in the second half of the contact phase (Fig. 4B), the most prominent being a caudal translation along the thoracic wall with a maximum of about 0.8 cm on average (Table 4). At the same time the center of rotation is translated laterally and ventrally.

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.