Date of Award
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Bachelor of Arts
Scott F. Gilbert
This thesis presents the latest evidence in a string of observations supporting a hypothesis of turtle shell development that alludes to the modularity of paracrine signaling pathways and their evolutionary cooption. Epithelial-mesenchymal interactions give rise to a diverse set of cutaneous appendages in vertebrates. It seems the early ontogeny of the Chelonian carapacial ridge-the epithelial-mesenchymal interaction responsible for the dorsoventral position of the ribs in turtles-is similar to that of scutate placodes and feather buds. Here, I report the expression of Shh and β-catenin in the ecotdermal tissue of the carapacial ridge of T. scripta embryos. Analysis of turtle explants with disrupted Fibroblast Growth Factor signaling, reveals that members of this family of paracrine factors are necessary for maintenance of proper carapacial ridge morphology. Also discussed is the possibility of visualizing the patterning of somite derivatives in these FGF-disrupted embryos, using riboprobes to Pax9 and antibodies to Pax7 in histological analyses. Through comparison with better characterized epithelial-mesenchymal interactions, a possible ontogeny of signaling events for the induction of the carapacial ridge is hypothesized. Several evolutionary implications are drawn, including a hypothesis of the role of various paracrine signals in the divergent patterns of dermal ossification observed in hard and soft-shelled turtles.
Riccio, Paul N. , '05, "Paracrine Signaling in the Carapacial Ridge of the Red-Eared Slider Turtle, Trachemys scripta" (2005). Senior Theses, Projects, and Awards. 61.