Sterile hybrids and fertile males transfer seminal products that trigger morphological changes of the uterus
Interrupted copulations showed significant differences between males from parental population and sterile male hybrids in proportion of seminal fluid masses present at two minutes interruptions (parentals= 87.5%; sterile males= 33.3%; Fisher-Exact test P = 1.3x10-8) but by six minutes the differences were non-significant (parentals= 97.7%; sterile males= 86.5%; Fisher-Exact test P = 0.068) (Table 2). This result shows that sterile males take longer, but effectively transfer seminal fluids. Moreover, the transfer of seminal fluids triggers similar morphological responses in the female reproductive tract of females mated to fertile or sterile males. The uterus is compacted in virgin females, with the seminal receptacle located ventrally (Figure 2A). By two minutes, the uterus experiences partial elongation acquiring a more oval shape and the seminal receptacle is displaced opposite to the gonopod (Figure 2B). At this point, the seminal fluid and possibly sperm (the ejaculate) can be sometimes detected as a darker mass inside the uterus (Figure 2B). By six minutes the uterus is fully elongated, with an oval shape, and both the ejaculate mass and the ejaculate plug are visible (Figure 2C). In females mated to sterile males, besides taking longer for the seminal fluid mass to be transferred (Table 2), a major noticeable difference is the lack of sperm within the seminal fluid mass transferred by sterile males into the uterus (Table 2) (Figures 2 D and 2E).