Nishizawa H.,Hanando Minami |
Nishizawa H.,Kyoto University |
Asahara M.,Kyoto University |
Kamezaki N.,Suma Aqualife Park
Zoological Science | Year: 2013
In the present study, we analyzed the ontogenetic scaling of humeri in the green turtle (Chelonia mydas) and loggerhead turtle (Caretta caretta). Green turtles have relatively thicker humeri than loggerhead turtles, indicating that the humerus of the green turtle can resist greater loads. Our results are consistent with isometry, or slightly negative allometry, of diameter in relation to length of the humerus in both species. Geometric similarity or isometry of the humerus in relation to body mass is supported by estimates of the cross-sectional properties of green turtles. Sea turtles are adapted for aquatic life, but also perform terrestrial locomotion. Thus, during terrestrial locomotion, which requires support against gravity, the observed scaling relationships indicate that there may be greater stress and fracture risk on the humeri of larger green turtles than on the humeri of smaller turtles. In aquatic habitats, in which limbs are mainly used for propulsion, the stress and fracture risk for green turtle humeri are estimated to increase with greater speed. This scaling pattern may be related to the possibility that smaller turtles swim at a relatively faster speed per body length. © 2013 Zoological Society of Japan.
Nagashima H.,Niigata University |
Shibata M.,Niigata University |
Taniguchi M.,Suma Aqualife Park |
Ueno S.,Suma Aqualife Park |
And 2 more authors.
Journal of Anatomy | Year: 2014
The turtle shell provides a fascinating model for the investigation of the evolutionary modifications of developmental mechanisms. Different conclusions have been put forth for its development, and it is suggested that one of the causes of the disagreement could be the differences in the species of the turtles used - the differences between hard-shelled turtles and soft-shelled turtles. To elucidate the cause of the difference, we compared the turtle shell development in the two groups of turtle. In the dorsal shell development, these two turtle groups shared the gene expression profile that is required for formation, and shared similar spatial organization of the anatomical elements during development. Thus, both turtles formed the dorsal shell through a folding of the lateral body wall, and the Wnt signaling pathway appears to have been involved in the development. The ventral portion of the shell, on the other hand, contains massive dermal bones. Although expression of HNK-1 epitope has suggested that the trunk neural crest contributed to the dermal bones in the hard-shelled turtles, it was not expressed in the initial anlage of the skeletons in either of the types of turtle. Hence, no evidence was found that would support a neural crest origin. © 2014 Anatomical Society.