Integrative and Comparative Biology Advance Access originally published online on June 1, 2007
Integrative and Comparative Biology 2007 47(3):401-408; doi:10.1093/icb/icm020
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The contribution of neural crest cells to the nuchal bone and plastron of the turtle shell
*Department of Biology, Swarthmore College, 500 College Avenue, Swarthmore, PA 19081 USA; Swarthmore College, presently at Department of Chemistry, University of Wisconsin, Madison, WI 53706; Science Division, Friends Central School, 1101 City Avenue, Wynnewood, PA 19096 USA; Biology Department, Millersville University, PO Box 1002, Millersville, PA 17551 USA
Correspondence: 1E-mail: sgilber1{at}swarthmore.edu
The origin of the turtle plastron is not well understood, and these nine bones have been homologized to the exoskeletal components of the clavicles, the interclavicular bone, and gastralia. Earlier data from our laboratory showed that the plastral bone-forming cells stained positively for HNK-1 and PDGFR
, two markers of skeletogenic neural crest cells. We have now shown that the HNK-1+ cells are also positive for p75 and FoxD3, affirming their neural crest identity. These cells originate from the dorsal neural tube of stage-17 turtle embryos, several days after the original wave of neural crest cells have migrated and differentiated. Moreover, we have demonstrated the existence of a staging area, above the neural tube and vertebrae, where these late-emigrating neural crest cells collect. After residing in the carapacial staging area, these cells migrate to form the plastral bones. We also demonstrate that one bone of the carapace, the nuchal bone, also stains with HNK-1 and with antibodies to PDGFR. The nuchal bone shares several other properties with the plastral bones, suggesting that it, too, is derived from neural crest cells. Alligator gastralia stain for HNK-1, while their ribs do not, thus suggesting that the gastralial precursor may also be derived from neural crest cells.
From the symposium "Linking Genes and Morphology in Vertebrates" presented at the annual meeting of the Society for Integrative and Comparative Biology, January 3–7, 2007, at Phoenix, Arizona.