Kawamura N, Yamashiki N, Saitoh H, Sahara K
Biology Laboratory,Rakuno Gakuen University, Ebetsu, Japan.
Zygote. 2001 May;9(2):159-66. doi: 10.1017/s0967199401001174.
Silkworm (Lepidoptera) males produce dimorphic sperm: nucleate eupyrene sperm and anucleate apyrene sperm. The eupyrene sperm are ordinary sperm to fertilise the eggs, while the function of apyrene sperm remains uncertain. After meiosis, 256 sperm cells are enclosed by a layer of cyst cells, forming a sperm bundle. We have previously documented that the nucleus of eupyrene sperm anchors to the head cyst cell, which locates at the anterior apex of the bundle, by an acrosome tubule-basal body assembly. Neither the basal body attachment to the nucleus nor the acrosome is seen in apyrene sperm, and the nuclei remain in the middle region of the bundle. Peristaltic squeezing starts from the anterior of the bundles in both types of sperm, and cytoplasmic debris of the eupyrene sperm, and both the nuclei and debris of apyrene sperm, are eliminated at the final stage of spermatogenesis. Since the irregularity of meiotic division in apyrene sperm is known, we used triploid silkworm males that show irregular meiotic division even in eupyrene spermatocytes and are highly sterile. The irregular nuclei of the triploid are discarded by the peristaltic squeezing just as those of the apyrene sperm. Transmission electron microscopic observations disclose the abnormality in the acrosome tubule and in the connection to the basal body. The peristaltic squeezing of sperm bundles in the silkworm appears to be the final control mechanism to eliminate irregular nuclei before they enter female reproductive organs.
家蚕（鳞翅目）雄性产生二态性精子：有核的真核精子和无核的无核精子。真核精子是使卵子受精的普通精子，而无核精子的功能尚不确定。减数分裂后，256个精子细胞被一层囊细胞包围，形成一个精子束。我们之前记录到，真核精子的细胞核通过顶体小管 - 基体组件锚定在位于精子束前端的头部囊细胞上。在无核精子中既看不到基体与细胞核的附着，也看不到顶体，细胞核留在精子束的中间区域。两种类型精子的蠕动挤压都从精子束的前端开始，真核精子的细胞质碎片以及无核精子的细胞核和碎片在精子发生的最后阶段被清除。由于已知无核精子减数分裂的不规则性，我们使用了三倍体家蚕雄性，它们即使在真核精母细胞中也表现出不规则的减数分裂，并且高度不育。三倍体的不规则细胞核就像无核精子的细胞核一样通过蠕动挤压被丢弃。透射电子显微镜观察揭示了顶体小管及其与基体连接的异常。家蚕精子束的蠕动挤压似乎是在不规则细胞核进入雌性生殖器官之前将其清除的最终控制机制。
