Drosophila seminal fluid proteins enter the circulatory system of the mated female fly by crossing the posterior vaginal wall

Seminal fluid proteins from males of many insect species affect the behavio r and physiology of their mates. In some cases, these effects result from e ntry of the proteins into the female's circulatory system. In the fruit fly Drosophila melanogaster, some seminal fluid proteins enter the female's ci rculatory system after transfer from the male while others remain confined within the reproductive tract. To address where and how seminal fluid prote ins enter the hemolymph of the mated female, we compared the kinetics of tr ansfer and localization in mated females of two seminal fluid proteins that enter the hemolymph (Acp26Aa and Acp62F) and one that does not (Acp36DE). We also generated transgenic flies that produce Acp26Aa tagged with Aequore a victoria green fluorescent protein (GFP) to monitor its transfer in vivo. We report that Acps enter the female circulatory system from the posterior vagina immediately after insemination. The ability of Acps to enter the fe male hemolymph correlates with their ability to cross the intima that lines the posterior vagina. The ventral posterior vagina is structurally unlike other parts of the female reproductive tract in that it lacks muscles. We h ypothesize that it has higher permeability thus affording access to the fem ale's circulatory system. (C) 1999 Elsevier Science Ltd. All rights reserve d.