title: Comparative study of the shell development of hard- and soft-shelled turtles.
abstract: 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.
authors.affiliation: Division of Gross Anatomy and Morphogenesis, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nagashima
authors.forename: Masahiro
authors.initials: M
authors.lastname: Shibata
authors.forename: Mari
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Shintaro
authors.initials: S
authors.lastname: Ueno
authors.forename: Naoki
authors.initials: N
authors.lastname: Kamezaki
authors.forename: Noboru
authors.initials: N
authors.lastname: Sato
mesh_terms: D060105:Animal Shells / Q000196:embryology* / Q000378:metabolism; D000818:Animals; D001846:Bone Development / Q000502:physiology*; D001842:Bone and Bones / Q000196:embryology* / Q000378:metabolism; D018959:CD57 Antigens / Q000378:metabolism; D000939:Epitopes / Q000378:metabolism; D005346:Fibroblast Growth Factors / Q000378:metabolism; D009432:Neural Crest / Q000196:embryology / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D000077278:RNA, Mitochondrial; D014426:Turtles / Q000196:embryology*; D051153:Wnt Proteins / Q000378:metabolism
chemical_list: D018959:CD57 Antigens; D000939:Epitopes; D000077278:RNA, Mitochondrial; D051153:Wnt Proteins; D005346:Fibroblast Growth Factors; D012313:RNA
keywords: carapace; marker genes; neural crest; plastron; turtles
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