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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

Joan Lin-Cereghino

Second Committee Member

Tara Thiemann


Sexual dimorphism is the phenotypic difference between males and females of the same species, but how these phenotypic differences arise is largely unstudied at the molecular level. It is understood that sexual selection, or competition for mates, drives sexual dimorphism, but more recently it has been suggested that resource partitioning, or niche pressure, may exert evolutionary pressure, leading to sexual dimorphism. Many members of the sarseilloid family of ostracods exhibit sexual dimorphism of their lateral eyes with males having an image forming eye, while females have a rudimentary eye limited to sensing light and dark. Ostracods progress through five instar stages of development before becoming an adult, and by studying expression levels of selected developmental genes at instar IV, V adult stages and embryos, the underlying expression pattern change that leads to phenotypic differences can be seen. By comparing the differences in expression between two sarseilloid species, Euphilomedes carcharodonta and Euphilomedes morini , we can see how these species develop their specific phenotypes. In E. carcharodonta and E. morini , the genes Sine oculis, Dachshund, Seven in absentia, Chaoptic, Protein Kinase C and Opsin show different expression patterns between groups. The highest expression levels of Sine oculis are in developing embryos when compared to other stages of development. Dachshund, Seven in absentia, Chaoptic, Protein Kinase C and Opsin show significantly different patterns in males or noticeable male trends, demonstrating that these genes are important in the development and function of the sexually dimorphic lateral eye. E. carcharodonta and E. morini show similar gene expression patterns suggesting that these patterns have been conserved over evolutionary time to produce the observed dimorphic morphology.





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