Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furocho, Chikusa-ku, Nagoya 464-8601, Japan,
Department of Regeneration Science and Engineering, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto 606-8507, Japan.
Zoolog Sci. 2021 Feb;38(1):67-71. doi: 10.2108/zs200135.
Almost all viviparous species possess male external genitalia; for example, the mammalian penis is an intromittent organ. Some live-bearing bony fish use their anal fins to assist in mating and internal fertilization. We previously reported a male-specific asymmetric curvature at the posterior end of the anal fin in , a viviparous fish of the family Goodeidae. However, three other goodeid species, , , and , examined in that study possessed lesser anal fin curvature modifications as compared to those in the anal fin of . Here, we report the second case of acute-angled curvature modification of the male anal fin in the family Goodeidae. We obtained a dead specimen of the goodeid species from a city zoo in Japan, and the morphological and histological analyses indicated an acute-angled asymmetric curvature of the posterior end of the anal fin in , similar to that observed in in the previous study. However, in our previous report, obtuse-angled modification was only observed in one other species, , and two species belonging to other genera, and Therefore, our findings suggest that the acute-angled curvature in the male anal fin has been developed in the genus .
几乎所有胎生动物都具有雄性外部生殖器；例如，哺乳动物的阴茎是一种交配器官。一些胎生骨鱼使用它们的臀鳍来协助交配和体内受精。我们之前报道过，在胎生鱼类 Goodeidae 家族的 中，臀鳍后端存在雄性特有的不对称弯曲。然而，在该研究中检查的另外三个 Goodeidae 物种 、 、 和 ，其臀鳍弯曲程度的变化小于 在分析中。在这里，我们报告了 Goodeidae 家族中第二个雄性臀鳍锐角弯曲的案例。我们从日本的一个城市动物园获得了一个 Goodeidae 物种 的死标本，形态学和组织学分析表明 臀鳍后端呈锐角不对称弯曲，类似于我们之前在 中观察到的情况。然而，在我们之前的报告中，仅在另一个 物种 中观察到钝角修饰，以及两个属于其他属的物种 和 因此，我们的研究结果表明，雄性臀鳍的锐角弯曲已经在 属中得到了发展。
