Within the Sperm Biology Group I am interested in ultimate and proximate causes of sperm storage. Currently I am involved in two projects.
Females of many animal species sustain sperm viable in their reproductive tract for extended periods (Brennan & Orr 2015, Trends Ecol Evol). I focus on female fruitflies who possess two types of sperm storage organs. The seminal receptacle is used for short-term sperm storage, the paired spermathecae are used for long-term sperm storage. Each spermatheca is surrounded by cells that secrete various substances, like antioxidants, antimicrobials, and metabolic enzymes, into the spermatheca (see picture). Those secretions likely support long-term sperm storage. I will determine the effect of spermathecal secretions on female sperm storage using the GAL4/UAS system using methods of metabolism and microscopy.
While developing protocols to assess sperm storage I became interested in
Measuring sperm quality using live/dead viability staining
Sperm viability is a widely applied measure of sperm quality in ecological, evolutionary and medical studies. However, due to technical and biological pitfalls, it may be problematic to use values of sperm viability per se. In collaboration with Ruijian Guo I developed a protocol that expresses sperm quality as the slope of the temporal decrease of viability in a stressor medium.
An example of dead-live sperm staining (red sperm are dead, i.e. damaged membranes, green ones alive):