Sperm competition and gamete interactions in a marine broadcast spawner

Sexual selection almost certainly began in the sea with broadcast spawning organisms, where mass spawning events generate intense reproductive competition among gametes. In this thesis, I applied a range of novel experimental techniques to investigate gamete-level sexual selection in the broadcast spawning mussel, Mytilus galloprovincialis. I developed and tested a fluorescent dye technique for tracking sperm in competition, and used it to demonstrate that eggs can moderate sperm competition using chemoattractants. Exploring the molecular mechanisms of this process, I found that chemoattractants induce differential sperm gene expression. Finally, I described complex patterns of sexual selection on multivariate sperm traits.