Copulation anatomy of Drosophila melanogaster (Diptera: Drosophilidae): wound-making organs and their possible roles

Males of several insect species inflict wounds on female genitalia during copulation. Such copulatory wounding also occurs in the fruit fly Drosophila melanogaster Meigen, 1830, one of the most important model organisms. Using a flash fixation technique with mating pairs of D. melanogaster, I examined the use and functions of the male phallic organ within the female reproductive tract. Paired components of the phallic organ (gonopods and two pairs of branches of the basal processes of the aedeagus) opened sequentially, from outer to inner components, during copulation. The dorsal branches of the aedeagal basal processes pierced the intima of the female reproductive tract at the lateral shallow folds. Consequently, mated females usually had a pair of melanized patches from repaired copulatory wounds. The sites that were stabbed by the dorsal branches were also clutched on the outside of the female oviscape (ovipositor) by the posterior process, which is a component of the periphallic organ. These structures likely function together as a mate-holding device. Male ejaculate labeled with rhodamine-B fluorescent dye entered the copulatory wounds in D. eugracilis Bock and Wheeler (Univ Texas Publ 7213:1-102, 1972), a related species, but not in D. melanogaster. Thus, copulatory wounds may function as an entrance for male seminal chemicals into the female circulatory system in D. eugracilis, but might not in D. melanogaster.