Kim Hyeon Jin, Park Jung Jun, Lee Jung Sick
Department of Aqualife Medicine, Chonnam National University, Yeosu, Republic of Korea.
Aquaculture Industry Research Division, East Sea Fisheries Research Institute, National Institute of Fisheries Science, Gangneung, Republic of Korea.
PLoS One. 2025 Jan 22;20(1):e0316519. doi: 10.1371/journal.pone.0316519. eCollection 2025.
The present study describes the differentiation process of male germ cells in Octopus vulgaris, the morphology of sperm in the testis and spermatophore, and the sperm released after the spermatophoric reaction. During spermatogenesis, the male sperm cell gradually elongates from a round shape, with cytoplasm shifting toward the head and the acrosome forming. Additionally, in the spermatid stage, the flagellum develops within the posterior nuclear channel and extends outside the cytoplasm. The sperm is composed of a head and a tail. The head is approximately 17.9 μm long and consists of a highly electron-dense nucleus and a helical acrosome. The tail is divided into three parts: the mid-piece, principal-piece, and end-piece. The mid-piece forms a mitochondrial sheath with 7-8 mitochondria surrounding a "9+2" axoneme. The principal-piece is composed of an axoneme, outer dense fibers, and fibrous sheath, while the end piece lacks outer dense fibers or fibrous sheath. The sperm in the testis and spermatophore, and the sperm released after the spermatophoric reaction have the same structure. However, in the sperm located in the testis and spermatophore, the structure of the acrosome is unclear due to the presence of cytoplasm in the head. In contrast, sperm released after the spermatophoric reaction lack their cytoplasm, revealing the helical acrosome. This unique sperm morphology, adapted for internal fertilization, is thought to be advantageous for fertilization and long-term storage within the female reproductive system.
本研究描述了普通章鱼雄性生殖细胞的分化过程、睾丸和精荚中精子的形态以及精荚反应后释放的精子。在精子发生过程中，雄性精子细胞从圆形逐渐拉长，细胞质向头部移动并形成顶体。此外，在精子细胞阶段，鞭毛在核后通道内发育并延伸到细胞质外。精子由头部和尾部组成。头部约17.9μm长，由高度电子致密的细胞核和螺旋形顶体组成。尾部分为三部分：中段、主段和末段。中段形成线粒体鞘，有7 - 8个线粒体围绕着“9 + 2”轴丝。主段由轴丝、外致密纤维和纤维鞘组成，而末段缺乏外致密纤维或纤维鞘。睾丸和精荚中的精子以及精荚反应后释放的精子具有相同的结构。然而，在睾丸和精荚中的精子，由于头部存在细胞质，顶体的结构不清楚。相比之下，精荚反应后释放的精子没有细胞质，露出螺旋形顶体。这种独特的精子形态适应体内受精，被认为有利于在雌性生殖系统内受精和长期储存。
