Females in taxa ranging from insects to mammals have evolved sperm storage mechanisms. Different organisms store different amounts of sperm for different lengths of time in closed or open reservoirs. Given its wealth of genetic and molecular tools and the high conservation of genes between flies and mammals, Drosophila promises to be an important model system for understanding the molecular basis of sperm-female interactions across animal taxa. Drosophila females have two types of sperm storage organs: paired spherical spermathecae and a single elongate, tubular seminal receptacle. Despite the interest in the evolution and function of the seminal receptacle, the structure of the receptacle epithelium has received little attention in Drosophila. We have used a correlative microscopy approach in which we combined confocal for light, X-ray microtomography for three-dimensional view of the whole organ and high resolution in vivo imaging with focused ion beam (FIB). This combination allowed an increased sample throughput gaining insights into the internal structure of the seminal receptacle. Each imaging technique revealed a different level of information about sperm localization within storage, outline of the organ and details about the internal structures. The obtained results open new avenues and allow new questions to be asked about sperm-female interactions post mating.
