Drosophila reproduction: Molecules meet morphology.

Our understanding of how male seminal fluid proteins (SFPs) influence the outcome of copulation in a wide range of insect taxa has been fueled primarily by studies of Drosophila (1). SFPs are known to localize, after copulation, to specific regions of the female reproductive tract and nervous system. Manipulative studies revealed that these proteins control a number of postcopulatory processes, such as sperm storage and retrieval and female egg production and remating (2). Proteins produced by the female reproductive tract have been identified (3, 4) and also mediate molecular interactions between the sexes. The influences of SFPs on female reproduction have been considered largely in a purely physiological way. A newly characterized and critical aspect of male–female interactions is revealed in the PNAS paper by Mattei et al. (5), who used micro-CT scans to prepare 3D reconstructions of the female reproductive tract before, during, and after mating. Copulation produces a dynamic series of dramatic conformational changes in the mated female reproductive tract, changes never visible previously in studies with dissected material. Moreover, Mattei et al. (5) demonstrate the roles of particular male seminal components in mediating these morphological changes inside the female. In the age of molecular biology and signaling, interest in more traditional descriptive disciplines, such as morphology, became obsolete. Now, however, we see that morphology is anything but static and that, in fact, the coordinated changes in morphology following mating are what are ultimately responsible for whether reproduction will be completed.