Positional strategy of trunk muscles among aquatic,semi-aquatic and
terrestrial species in Urodela |
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Authors: | Ayano OMURA Wataru ANZAI Daisuke KOYABU Hideki ENDO |
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Institution: | 1)Graduate School of Agricultural and Life Sciences, The University Museum, The University of Tokyo, 7–3–1 Hongo, Bunkyo-ku, Tokyo 113–0033, Japan;2)Graduate School of Biological Sciences, The University Museum, The University of Tokyo, 7–3–1 Hongo, Bunkyo-ku, Tokyo 113–0033, Japan;3)The University Museum, The University of Tokyo, 7–3–1 Hongo, Bunkyo-ku, Tokyo 113–0033, Japan |
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Abstract: | Clarification of the trunk structure in Urodela is important in understanding the
locomotive evolution of basal tetrapods. The components of the muscular trunk wall among
Urodela using different modes of locomotion were compared. Since the whole trunk may be
used for swimming and the effect of limbs may be small in the more aquatic species, they
showed smaller differences in the trunk muscles among anterior, middle and posterior
sections of the trunk. By contrast, in the more terrestrial species, the dorsal and
abdominal muscles are larger in the middle section than those in the anterior and
posterior sections. High compressive stresses occur in the supporting limbs and their
insertion at the trunk on the ventral side, and spread from the forelimbs along the back
to the supporting hindlimbs on the dorsal side. Tensile stresses occur in the middle
ventral part. The components of the trunk muscles among the three sections may reflect
differences in stresses occurring in the trunk of the more terrestrial species. The
findings also suggest that in the middle section, larger dorsal muscles for stiffening the
back to maintain posture and larger abdominal muscles are responsible for balancing the
body weight while it is supported by the limbs in the more terrestrial species. |
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Keywords: | axial muscle Caudata locomotion salamander Urodela |
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