Fig. 1.

Human and fly reproductive systems. (A and B) Schematics illustrate male reproductive systems of humans (A) and flies (B). Note red-shaded secretory organs in both organisms contribute much of the volume of seminal fluid, many key proteins, and nutrients, and are critical for normal fertility. (C) Fly female reproductive system includes two different sperm storage organs (shaded green), the paired spermathecae and the seminal receptacle. They gradually release sperm after mating under the control of SP, which is itself slowly released from its binding sites on sperm. Females also have two small secretory accessory glands. (D) Confocal image of paired accessory glands (arrows). In this whole mount, the 40 secondary cells in the epithelium express GFP (green), but the more abundant main cells do not. The preparation is stained with TRITC-phalloidin, which highlights the striated muscle layer (red) surrounding the gland that undergoes peristaltic contraction upon mating, and DAPI (blue), which marks the nuclei.