A FEMALE NERVOUS-SYSTEM IS NECESSARY FOR NORMAL SPERM STORAGE IN DROSOPHILA-MELANOGASTER - A MASCULINIZED NERVOUS-SYSTEM IS AS GOOD AS NONE

A male Drosophila melanogaster deposits many more sperm in a female's bursa copulatrix than are stored in her ventral receptacle or paired s permathecae soon after copula has ended. The remaining sperm are expel led by the female. These observations suggest a sexual conflict over t he processes involved in sperm storage. We used genetically manipulate d flies to study the role of the central nervous system in sperm stora ge. Flies with female bodies but masculinized nervous systems, or isol ated female abdomens, stored significantly fewer sperm than did contro l females. Furthermore, compared with central flies, there were relati vely more sperm in the ventral receptacle and relatively fewer in the spermathecae. These results suggest that the female nervous input coun teracts the male's attempts to force sperm into the ventral receptacle during copula and promotes active transport of sperm to the spermathe cae during and after copula. The female is clearly a very active partn er in influencing processes involved in sperm competition, especially as only stored sperm can be used later to fertilize eggs. To our knowl edge, this is the first study to show directly the involvement of the female nervous system in sperm storage.