Seminal fluid protein

In many animals with internal fertilization, males transfer a complex cocktail of proteins in their semen to females during copulation.

Seminal fluid proteins frequently show evidence of elevated evolutionary rates and are often cited as an example of sexual conflict.

SFPs show elevated rates of DNA sequence change compared to non-reproductive genes (measured by Ka/Ks ratio) in many orders, including Diptera (flies),[9][10] Lepidoptera (butterflies and moths),[1] Rodentia,[11] and Primates.

[15] Many D. melanogaster SFP genes are expressed by the female reproductive tract, particularly within the sperm storage organs, which may be more consistent with roles supporting spermatozoa than in sexual conflict.

[18] SFPs lengthen the refractory period (when the female is disinterested in mating) and stimulate ovulation; additionally they can affect processes such as sperm storage, metabolism, and activity levels.