Cheng Zixin, Kamimura Yoshitaka, Ferreira Rodrigo L, Lienhard Charles, Yoshizawa Kazunori
Systematic Entomology, School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.
Department of Biology, Keio University, Yokohama 223-8521, Japan.
R Soc Open Sci. 2023 Jan 11;10(1):220471. doi: 10.1098/rsos.220471. eCollection 2023 Jan.
Brazilian sex-role reversed cave insects (genus ) have a striking structure called the gynosome (or female penis), which deeply penetrates male vagina-like genitalia during copulation to receive nutritious semen. However, the protruding and retracting mechanisms of the female penis, including their evolutionary origin, are poorly understood. By using micro-computed tomography (µCT), we compared the genital morphology and musculature between species with a gynosome and others lacking this structure. As a result, we discovered two groups of muscles related to the protrusion and retraction of gynosomes. These muscles were also observed in species with non-protrusible prepenis. This suggests that evolution of these muscles preceded the acquisition of the protruding function of the gynosome, originally having a putative stimulatory function to receive nutritious semen. This intermediate stage probably allowed for the reversal of genital functions.
巴西性别角色反转的洞穴昆虫（属）具有一种名为雌体性器官（或雌性阴茎）的显著结构，在交配过程中，该结构会深深插入雄性类似阴道的生殖器中以接收富含营养的精液。然而，雌性阴茎的伸出和缩回机制，包括它们的进化起源，目前还知之甚少。通过使用微计算机断层扫描（µCT），我们比较了具有雌体性器官的物种和其他缺乏该结构的物种之间的生殖器形态和肌肉组织。结果，我们发现了两组与雌体性器官的伸出和缩回相关的肌肉。在具有不可伸出的阴茎前体的物种中也观察到了这些肌肉。这表明这些肌肉的进化先于雌体性器官伸出功能的获得，最初可能具有一种假定的刺激功能以接收富含营养的精液。这个中间阶段可能促成了生殖器功能的反转。
