Dahl J F, Gould K G, Nadler R D
Yerkes Regional Primate Research Center, Emory University, Atlanta, Georgia 30322.
Am J Phys Anthropol. 1993 Feb;90(2):229-36. doi: 10.1002/ajpa.1330900209.
Few data are available for assessing the relative testicle size of orang-utans, Pongo pygmaeus, so measures were obtained for 31 individuals of varying age. It was shown that the volume of the testicles, calculated from in situ measures of testicle length and breadth, closely approximates testicle weight when multiplied by the specific gravity of solid tissue. Growth curves for body weight and data published for wild specimens were evaluated to obtain the weight most characteristic of male Pongo, and the ratio of testicle weight to body weight was calculated. The mean ratio for individuals with fully adult stature is 0.034, similar to but smaller than that of humans at about 0.050, and larger than the ratios reported for 5 gorillas at 0.013. The testicles mature faster than the body, however, so the mean ratio for young adult orang-utans is about 0.056 and resembles the ratio for humans more closely than the full adults. The differences between the ratios for a monogamous gibbon species, orang-utans, and humans is accounted for when testicle size relative to the weight of the female is considered. This is consistent with a sperm dilution effect produced by variation in the size of the female reproductive tract. The small relative testicle size of the gorilla is anomalous and requires verification as does the application of female size to scale the testicles.
关于评估红毛猩猩（Pongo pygmaeus）睾丸相对大小的数据很少，因此我们对31只不同年龄的个体进行了测量。结果表明，根据睾丸长度和宽度的原位测量值计算出的睾丸体积，乘以实体组织的比重后，与睾丸重量非常接近。评估了体重的生长曲线以及野生标本公布的数据，以得出雄性红毛猩猩最具代表性的体重，并计算出睾丸重量与体重的比值。成年个体的平均比值为0.034，与人类的比值（约0.050）相似但略小，比报道的5只大猩猩的比值（0.013）大。然而，睾丸比身体成熟得更快，因此年轻成年红毛猩猩的平均比值约为0.056，比成年个体更接近人类的比值。当考虑睾丸大小相对于雌性体重的比例时，一夫一妻制长臂猿物种、红毛猩猩和人类之间的比值差异就可以得到解释。这与雌性生殖道大小变化产生的精子稀释效应是一致的。大猩猩相对较小的睾丸大小是反常的，需要验证，将雌性大小应用于睾丸大小的缩放也需要验证。
