Fishery Research Laboratory, Kyushu University, 4-46-24, Tsuyazaki, Fukutsu 811-3304, Japan.
Mindanao State University-Naawan, Pedro Pagalan St. Poblacion, Naawan, 9023 Misamis Oriental, Philippines.
Zoolog Sci. 2020 Dec;37(6):519-528. doi: 10.2108/zs200080.
is a fully segmented worm with complete intersegmental septa. A previous study of females revealed that germ cells of this animal originate in the tail end segment, called the pygidium. Germ cells were duplicated in the pygidium, transferred to a newly generated segment, and then settled in the parapodia. Within each segment, the settled germ cells proliferated in the parapodia and then migrated into a body cavity area to begin meiotic development. Currently, there is not much information about differences between male and female germ cell development. Therefore, we conducted monthly in situ hybridization analyses using the germ cell marker Pn-piwi and histological examinations. Germ cells detected by Pn-piwi initially settled in the distal areas of the parapodia on both sides of each segment, then formed a large germ cell cluster in each parapodium, and finally, small germ cell clusters were formed by the separation of the large clusters. The small clusters migrated to the deeper body cavity area during growth by segment addition. Until the female germ cells began vitellogenesis, the sex of germ cells could not be identified by morphological observation. Thus, male and female may have the same mechanism of germ cell provision to all segments. At the time of spawning, sperm were released from nephridiopores at the 2 through 15 segments from the pygidium, while eggs were released through ruptures in the skin of 2-3 segments between the 10 and 30 segments from the tail.
是一条完全分节的蠕虫，具有完整的体节间隔膜。之前对雌性的研究表明，这种动物的生殖细胞起源于尾部末端的节段，称为尾节。生殖细胞在尾节中复制，转移到新生成的节段，然后定居在附肢中。在每个节段内，定居的生殖细胞在附肢中增殖，然后迁移到体腔区域开始减数分裂发育。目前，关于雄性和雌性生殖细胞发育之间的差异没有太多信息。因此，我们使用生殖细胞标记 Pn-piwi 进行了每月的原位杂交分析和组织学检查。Pn-piwi 检测到的生殖细胞最初在每个节段两侧附肢的远端区域定居，然后在每个附肢中形成一个大的生殖细胞簇，最后，大簇通过分离形成小的生殖细胞簇。随着节段的增加，小簇通过生长迁移到更深的体腔区域。直到雌性生殖细胞开始卵黄生成，通过形态观察无法确定生殖细胞的性别。因此，雄性和雌性可能具有向所有节段提供生殖细胞的相同机制。在产卵时，精子从尾节的 2 到 15 节的肾孔中释放，而卵子从 10 到 30 节之间的 2-3 节的皮肤破裂中释放。
