Within an ejaculate, natural selection favors substances that activate and nourish sperm and that are thus essential for proper fertilization of oocytes. Additionally, post-copulatory sexual selection favors the evolution of seminal substances that further enhance fertilization chances by influencing female Terbinafine hydrochloride physiology, which thereby fall within the definition of allohormones. Selection for such substances is strongly enhanced when sperm recipients store sperm, mate promiscuously and have specialized sperm-digesting organs, because sperm donors that manipulate these processes to the advantage of their sperm��s fertilization chances will have a clear evolutionary advantage. Indirect evidence for the presence of such substances is abundant, but very few studies have attempted to unravel their identities. Moreover, although focus has been almost exclusively on separate sex species, we demonstrate here that such substances have also evolved in simultaneous hermaphrodites. By far the best studied system in separate sex species, in which seminal peptides provide clear reproductive fitness advantages to males, is the fruit fly Drosophila melanogaster. Approximately 20 accessory gland proteins have been identified and numerous other proteins have been shown to be transferred along with the sperm. These peptides affect females in several ways. For example, Acp70A decreases female receptivity and increases egg production. Furthermore, Rice showed, using an experimental evolution approach, that more competitive ejaculates can be detrimental to the survival of females. This reduced survival is most likely D-glutamine caused by Acp62F, which seems to protect sperm within the female tract but at the same time has a toxic effect on the female. Recently, an additional example of an identified substance promoting sperm storage in the female emerged from analyses of the mating plug of the mosquito Anopheles gambiae. There are also several detailed studies into the composition of seminal fluids, e.g., the honey bee Apis mellifera and the sea urchin Lytechinus variegatus but these have not included functional tests.