Date of Award


Document Type

Restricted Thesis

Terms of Use

© 1999 Rachel Rose Gutman Reich. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Biology Department

First Advisor

Scott F. Gilbert


The turtle shell is an evolutionary novelty composed of two main parts, the dorsal carapace and the ventral plastron. The carapace is supported by the ribs which grow dorsolaterally rather than ventrally. These two unique features, possession of a bony shell and dorsal ribs, represent a departure from the standard vertebrate bauplan. The critical event in turtle development and evolution is thought to be the "ensnarement" of the ribs by the carapacial ridge, a bulge of mesoderm and ectoderm resembling the limb bud. We examined the spatiotemporal expression pattern of two genes in Trachemys scripta elegans, the red-eared slider, in order to gain a better understanding of how the carapace develops. These genes are fibroblast growth factor 10, fgf10, a paracrine factor thought to be critical in specifying which lateral tissues become limb buds, and Hoxc-6, a homeobox gene and transcription factor whose anterior boundary of expression correlates with the first rib-forming thoracic vertebrae. We were unable to amplify fgf10 in Trachemys scripta elegans using RT-PCR with three different sets of primers. One possible explanation for this result is that turtles may not have fgf10. Hoxc-6 is thought to have been successfully amplified although the PCR product was not cloned or sequenced.