The traits I am particularly interested in are how the morphology, production and use of gametes, and the interactions between sperm and eggs, influence reproductive success. One of my primary interests is in the evolution of sperm heteromorphism. Males in this group produce two sperm types, short sperm that has both a short head and flagellum, relative to long sperm. The evolutionary significance of this phenomenon is unknown in Drosophila . Males produce species-specific proportions of each sperm type.
Males transfer to females both sperm types in the same ratio that males produce.
Females store both sperm types, although the length of time short sperm are stored varies among species. Short and long sperm of D. affinis . This observation led to the question of why short sperm are not behaving as gametes and whether they serve any adaptive function. I found that short sperm do not contribute significantly as a nutrient contributions to either females or oocytes. I also found that they do not function to delay female remating behavior, thereby postponing sperm competition.