Microscopic Techniques for Studying Sperm-Oocyte Interaction During Fertilization and Early Embryonic Development

The union between sperm and oocyte is species-specific, and the courses of events that follow are some of the most dramatic surrounding fertilization and early development. How does the highly motile, yet very small, sperm from one species recognize the immotile, very large oocyte from its own species? How does the sperm penetration and subsequent membrane fusion take place? What happens to this successful sperm inside the ooplasm prior to decondensation and pronuclear fusion? What is the best microscopy method to capture these events? Questions such as these have been asked ever since humans have questioned their own existence on the cellular level. Only recently have molecular answers to these questions been found. The use of the electron microscope has increased our appreciation of these events because of its outstanding resolution. However, specimen preparation captures events in a static fashion. New optical techniques offer promise in the investigation of these events in real time.