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Date of Award


Document Type

Thesis - Pacific Access Restricted

Degree Name

Master of Science (M.S.)


Biological Sciences

First Advisor

Ajna Rivera

First Committee Member

Gregg D. Jongeward

Second Committee Member

Douglas C. Weiser


The genetics of switchback evolution is largely unknown. While it is assumed that latent gene regulatory networks become reactivated to recreate an ancestral tissue, the details regarding this reactivation has yet to be elucidated. How has a network been maintained over the evolutionary history of this group? Are certain genes within these pathways more susceptible to suppression than other genes? In this study, I examined Euphilomedes carcharodonta, a member of the Sarsielloidea superfamily of ostracods, a clade which has demonstrated the loss and regain of the lateral eye multiple times over its evolutionary history. In particular, I looked at the genetic mechanisms for the development of the sexually dimorphic lateral eye, in which males have large, multifaceted image-forming eyes typical to those of other pancrustaceans (Hexapoda+Crustacea) while females do not. This sexual dimorphism is of particular interest because it allows me to study the genetic underpinnings of a regained trait using individuals of near-identical genetic backgrounds, as these organisms have a singlechromosome sex determination system (XXIXO).

Examination of developmental eye genes ec-Dachshund, ec-Daughtless, ecChaoptic, ec-Shaven, and ec-Epidermal growth factor receptor showed differential gene expression patterns in which juvenile male eyes expressed these genes at a higher level than did juvenile female eyes. These genes are thus candidate genetic components of 6 switchback evolution, as this data is a first step towards comparative transcriptomics and gene expression studies comparing multiple species.



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