Parga Joyce A, Maga Murat, Overdorff Deborah J
Department of Anthropology, University of Texas at Austin, Austin, Texas 78712, USA.
Am J Phys Anthropol. 2006 Apr;129(4):567-76. doi: 10.1002/ajpa.20281.
In this study, high-resolution computed tomography X-ray scanning was used to scan ring-tailed lemur (Lemur catta) copulatory plugs. This method produced accurate measures of plug volume and surface area, but was not useful for visualizing plug internal structure. Copulatory plug size was of interest because it may relate to male fertilization success. Copulatory plugs form from coagulated ejaculate, and are routinely displaced in this species by the penis of a subsequent mate during copulation (Parga [2003] Int. J. Primatol. 24:889-899). Because one potential function of these plugs may be to preclude or delay other males' successful insemination of females, we tested the hypothesis that larger plugs are more difficult for subsequent males to displace. Plugs were collected opportunistically upon displacement during data collection on L. catta mating behavior on St. Catherines Island, Georgia (USA) during two subsequent breeding seasons. Copulatory plugs exhibited a wide range of volumes: 1,758-5,013.6 mm3 (n = 9). Intraindividual differences in plug volume were sometimes greater than interindividual differences. Contrary to predictions, larger plugs were not more time-consuming for males to displace via penile intromission during copulation. Nor were plugs with longer vaginal residence times notably smaller than plugs with shorter residence times, as might be expected if plugs disintegrate while releasing sperm (Asdell [1946] Patterns of Mammalian Reproduction; Ithaca: Comstock). We found a significant inverse correlation between number of copulatory mounts leading to ejaculation and copulatory plug volume. This may indicate that if males are sufficiently sexually aroused to reach ejaculation in fewer mounts, they tend to produce ejaculates of greater volume.
在本研究中，使用高分辨率计算机断层扫描X射线扫描来扫描环尾狐猴（Lemur catta）的交配栓。该方法能准确测量交配栓的体积和表面积，但对于观察交配栓的内部结构并无帮助。交配栓的大小令人感兴趣，因为它可能与雄性的受精成功率有关。交配栓由凝固的精液形成，在该物种中，后续交配时，交配栓通常会被后续配偶的阴茎在交配过程中顶出（帕尔加[2003]《国际灵长类学杂志》24:889 - 899）。由于这些交配栓的一个潜在功能可能是防止或延迟其他雄性使雌性成功受精，我们检验了这样一个假设：较大的交配栓对后续雄性来说更难顶出。在美国佐治亚州圣凯瑟琳斯岛对环尾狐猴交配行为进行数据收集的两个后续繁殖季节中，在交配栓被顶出时随机收集。交配栓的体积范围很广：1758 - 5013.6立方毫米（n = 9）。个体内交配栓体积的差异有时大于个体间的差异。与预测相反，在交配过程中，雄性通过阴茎插入顶出较大的交配栓并不需要更多时间。而且，阴道停留时间较长的交配栓也并不明显小于停留时间较短的交配栓，而如果交配栓在释放精子时会分解，情况可能会如预期的那样。我们发现导致射精的交配次数与交配栓体积之间存在显著的负相关。这可能表明，如果雄性受到足够的性刺激，在较少的交配次数中就能达到射精，那么它们往往会产生体积更大的精液。
