Locomotion pattern and trunk musculoskeletal architecture among Urodela.
We comparatively examined the trunk musculature and prezygapophyseal angle of mid-trunk vertebra in eight urodele species with different locomotive modes (aquaticSiren intermedia,Amphiuma tridactylum,Necturus maculosusandAndrias japonicus; semi-aquaticCynops pyrrhogaster, Cynops ensicauda; and terrestrialHynobius nigrescens,Hynobius lichenatusandAmbystoma tigrinum). We found that the more terrestrial species were characterized by larger dorsal and abdominal muscle weight ratios compared with those of the more aquatic species, whereas muscle ratios of the lateral hypaxial musculature were larger in the more aquatic species. The lateral hypaxial muscles were thicker in the more aquatic species, whereas theM. rectus abdominiswas more differentiated in the more terrestrial species. Our results suggest that larger lateral hypaxial muscles function for lateral bending during underwater locomotion in aquatic species. Larger dorsalis and abdominal muscles facilitate resistance against sagittal extension of the trunk, stabilization and support of the ventral contour line against gravity in terrestrial species. The more aquatic species possessed a more horizontal prezygapophyseal angle for more flexible lateral locomotion. In contrast, the more terrestrial species have an increasingly vertical prezygapophyseal angle to provide stronger column support against gravity. Thus, we conclude trunk structure in urodeles differs clearly according to their locomotive modes.
Graduate School of Agricultural and Life Sciences, The University Museum, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan ; The University Museum, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Ayano
A
Omura
Department of Oral and Maxillofacial Radiology, Nihon University School of Dentistry 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan.
Ken-Ichiro
KI
Ejima
Department of Oral and Maxillofacial Radiology, Nihon University School of Dentistry 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan ; Division of Systemic Biology and Oncology, Dental Research Center, Nihon University School of Dentistry 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan.
Kazuya
K
Honda
The University Museum, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan ; Graduate School of Biological Sciences, The University Museum, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Wataru
W
Anzai
Hiroshima City Asa Zoological Park, Asa-tyou Doubutsuen Asakita-ku, Hiroshima City, Hiroshima, 731-3355, Japan.
Yuki
Y
Taguchi
The University Museum, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Daisuke
D
Koyabu
The University Museum, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Hideki
H
Endo
Urodela; locomotion; muscle; trunk; vertebra