Drosophila females have two types of internal sperm storage organs. Spermathecae - a pair of long-term sperm storage and seminal receptacle - a short term storage. The seminal receptacle is an elongated closed end tubular structure. The sperm cells keep motility during storage in it for several weeks with no docking period as in mammalians or further activation. The seminal receptacle provides a microenvironment that maintains the active, motile sperm. Thus, it is possible that motile sperm interact with molecules secreted by the epithelium and that this sperm-female interaction plays a role in maintaining and/or regulating sperm functionality. There is relatively little known and much to be learned about the factors that govern sperm storage in the female reproductive tract.
Using a triple correlative approach of confocal, micro-CT and FIB-SEM we were able to observe the location of sperm in the seminal receptacle and to begin to dissect sperm-epithelium interactions at high resolution.
This is the first attempt to study sperm-female interactions using a correlative approach. Sperm-female interactions are mostly unknown, mainly because they occur within the receptacle`s confined small space (approx. 10-20 microns) which house hundreds of 0.5-micron thick long sperm. The triple correlative approach opens up a window to a completely new level of high-resolution information at the cellular level. Thus, having in hand such a system we can now begin to address questions related to sperm-female interactions. Furthermore, such a system is suitable not only for Drosophila but also for other organisms with soft delicate tissues.
