Date of Award


Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy (PhD)


Environmental Sciences

First Advisor

Helen C. Poynton

Second Advisor

Michael F. Tlusty

Third Advisor

Juanita Urban-Rich


Sex determination and differentiation in metazoans are dynamic processes involving genetic and environmental factors. Both of these processes are tightly linked where sex determination directly informs sex differentiation. Though Mollusca is the second most diverse animal phylum, behind Arthropoda, sex differentiation is understudied in this group, especially bivalves. Greater foundational research into bivalve sex differentiation is required to understand the complexity of this process and the ways outside forces, such as xenobiotics and parasites, may perturb sex differentiation. The purpose of this research is to identify and characterize sex differentiating genes in the blue mussel, Mytilus edulis, and disruptions to the male/female phenotypes. A phylotranscriptomics approach identified putative sex differentiating genes across Bivalvia and characterized their sex-specific expression in M. edulis. Following, mussels were exposed to two endocrine disrupting compounds to induce a sex change. These compounds induced a sex reversal in some mussels and flipped expression of sex differentiating genes. Transcriptomic profiling using RNA-seq assessed the effects in mussel populations from polluted estuaries that are known to be experiencing endocrine disruption. The expression of putative sex differentiating genes and gonadal development were measured over an annual cycle to link these genes to sex differentiation. Finally, the effects of a parasitic trematode were determined in mussels, with particular emphasis on gonadal development. Overall, this research provides critical foundational research on bivalve sex differentiation and associated disruptions to this process.


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