| Fertilization in most animals requires the fusion of a single sperm per egg, or monospermy. Animals have evolved multiple methods that favor this one-to-one gamete ratio, including alternative mating behavior, specialized reproductive anatomy, and modifications to the egg cell surface following fertilization. Physical alteration of the egg extracellular matrix is a typical mechanism used to establish a permanent block against polyspermy. In echinoderms such as the sea urchin, the egg extracellular matrix is extensively modified to form the fertilization envelope, a distinct physical structure that serves as a barrier to both supernumerary sperm and environmental hazards. The research presented here focuses on the molecular aspects of fertilization envelope formation. I characterize the major structural components required for fertilization envelope assembly in the sea urchins Strongylocentrotus purpuratus and Lytechinus variegatus, specifically defining the protein network into which they autonomously assemble. I also identify and characterize the hydrogen peroxide generator required for fertilization envelope maturation. Together, these results detail some of the critical mechanisms used to construct the sea urchin fertilization envelope, and provide insight for complementary molecular mechanisms participating in the transition from an egg into an embryo. The implications of my results are evaluated in the context of the general animal block to polyspermy. |
