The Study On The Movement And The Competition Mechanism Of The Drosophila’s Sperm

For most organisms, multiple mating can lead to competition among different male sperms. The second or later males have more paternity proportion than the first. We call this phenomenon postcopulatory sexual selection. Species competition is one of Darwin’s important theory of natural selection, but Darwin’s theory does not answer why later males always have more offspring. In the study of evolutionary biology, it has been highly concerned of the explain of postcopulatory sexual selection, Previous hypotheses put forward the hypothesis of choosing to use, the hypothesis of difference reject or the hypothesis of sperm replace, the hypothesis of sperm inactivation to explain the mechanism of sexual selection after mating, however, there is no consensus as to this issue. Therefore, space-time and dynamic observing of sperm activity is the crucial issue to further uncover postcopulatory sexual selection.In order to observe the dynamics of sperm movement, and initially explore the factors affecting the sperm motility, to further explain the mechanism of the sperm competition.In this study, we will utilize GFP report gene of fruit flies to further observe the sperm dynamic process directly, based on different mating system, including protb E-GFP/TM3males(p, green fluorescent tags on the head) and DJ-GFP/CYO males(D, green fluorescent tags on the tail).By dissecting the different mated female we found:1.The movement pattern of Drosophila’s sperm in the female reproductive tract is:the tail drives the head to move, when the seminal vesicle independent of the reproductive system, the sperm can still be free access to the seminal vesicles; when the seminal vesicle is stretched, the sperm can still move; and moreover if the seminal vesicles and reproductive systems are separated, the sperm can still access to the seminal vesicles. 2.In the times (four times) mating system, the number of the sperm’s retention in the female, there is no significant difference by the first, second, and third mating. And the sperm can coexist in the female reproductive system, the sperm of the later male consume significantly less than the number of the first male.The results show that sperm motility of sperm competition is uncontrolled by the female’s reproductive system, there is no sperm replacing. The later sperm can not kill the front sperm, the first male sperm consumption significantly waste more than the later males, resulting in most of the first male sperm can not participate in fertilization process, which may explain why always later males have more offspring. The biological mechanism needs further study.