Shibata Daisuke, Morita Masaya, Sato Yu, Shiba Kogiku, Kitanobo Seiya, Yokoya Ryo, Inaba Kazuo
Shimoda Marine Research Center, University of Tsukuba, Shizuoka, Japan.
Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Okinawa, Japan.
Front Cell Dev Biol. 2022 Jun 27;10:905748. doi: 10.3389/fcell.2022.905748. eCollection 2022.
Parasperm are non-fertilizing sperm that are produced simultaneously with fertile eusperm. They occur in several animal species and show considerable morphological diversity. We investigated the dynamics of axonemes during paraspermatogenesis in the marine snail . Mature parasperm were characterized by two lateral undulating membranes for motility and many globular vesicles. Axonemes were first observed as brush-like structures that extruded from the anterior region. Multiple axonemes longer than the brush then started to extend inside the cytoplasm towards the posterior region. The mass of the axonemes separated into two lateral rows and formed an undulating membrane that drives bidirectional swimming in the mature parasperm. The central pair of axonemes was aligned in the undulating membrane, resulting in cooperative bend propagation. During paraspermatogenesis, centrioles were largely diminished and localized to the anterior region. CEP290, a major component of the transition zone, showed a broad distribution in the anterior area. Axonemes in the posterior region showed a 9 + 0 structure with both outer and inner arm dyneins. These observations provide a structural basis for understanding the physiological functions of parasperm in marine reproductive strategies.
副精子是与可育真精子同时产生的无受精能力的精子。它们存在于多种动物物种中，表现出相当大的形态多样性。我们研究了海蜗牛副精子发生过程中轴丝的动态变化。成熟的副精子的特征是有两个用于运动的侧向波动膜和许多球状小泡。轴丝最初表现为从前部区域伸出的刷状结构。然后，比刷状结构更长的多个轴丝开始在细胞质内向后部区域延伸。轴丝团分成两排侧向排列，并形成一个波动膜，驱动成熟副精子进行双向游动。中央的一对轴丝在波动膜中排列整齐，导致协同弯曲传播。在副精子发生过程中，中心粒大量减少并定位于前部区域。过渡区的主要成分CEP290在前部区域广泛分布。后部区域的轴丝呈现9 + 0结构，同时具有外臂和内臂动力蛋白。这些观察结果为理解副精子在海洋繁殖策略中的生理功能提供了结构基础。
