Harshman Lawrence G, Prout Timothy
Department of Entomology, University of California, Davis, California, 95616.
Department of Evolution and Ecology, University of California, Davis, California, 95616.
Evolution. 1994 Jun;48(3):758-766. doi: 10.1111/j.1558-5646.1994.tb01359.x.
In this paper we show that when Drosophila melanogaster females are mated twice, the semen of the second male causes a reduction of the effective number of resident sperm from the previous mating. This is demonstrated by two different kinds of experiments. In one set of experiments, mated females were remated to two different kinds of sterile males, one with normal semen and the other with deficient semen. The effect on the resident sperm was determined from the number of remaining progeny after mating to the sterile male, with the result that the normal semen reduced the amount of resident sperm in comparison with matings to the males with deficient semen. The second set of experiments employed interrupted matings. These experiments were based on the observation that semen is delivered before sperm during the first 5 min of copulation. The second matings were interrupted instantly, 2 min, and 4 min after the initiation of copulation. Compared to the instant interruptions, the two later interruptions had the effect of reducing the amount of resident sperm. The results of these two experiments clearly indicate that a sperm-incapacitation process plays a role in the well-documented phenomenon of sperm displacement (last-male advantage) in this species. Such a process could play a role in sperm displacement in the many cases where the mechanism is unknown.
在本文中，我们表明，当黑腹果蝇雌性进行两次交配时，第二只雄性的精液会导致来自前一次交配的驻留精子有效数量减少。这通过两种不同类型的实验得到了证明。在一组实验中，已交配的雌性再次与两种不同类型的不育雄性交配，一种具有正常精液，另一种精液不足。通过与不育雄性交配后剩余后代的数量来确定对驻留精子的影响，结果是与精液不足的雄性交配相比，正常精液减少了驻留精子的数量。第二组实验采用了中断交配。这些实验基于这样的观察，即在交配的前5分钟内精液在精子之前排出。第二次交配在交配开始后立即、2分钟和4分钟被中断。与立即中断相比，后两次中断具有减少驻留精子数量的效果。这两个实验的结果清楚地表明，精子失能过程在该物种中精子替代（最后交配雄性优势）这一有充分记录的现象中起作用。在许多机制未知的情况下，这样的过程可能在精子替代中起作用。
