 However, neither the first or second mate know if it his sperm that was dispelled, because at any postcopulatory moment a female can store the sperm of more than one male.Enzymes secreted by female reproductive tracts may also play a role in sexual antagonistic coevolution with males.In Drosophila species, a large group of enzymes known as serine proteases have been associated with female sperm storage organs (most notably, the spermatheca) through genetic sequencing and analysis.