Ikenaga Jumpei, Hookabe Natsumi, Kohtsuka Hisanori, Yoshida Manabu, Kajihara Hiroshi
Misaki Marine Biological Station, The University of Tokyo, Misaki, Miura, Kanagawa 238-0225, Japan.
Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0180, Japan.
Zoolog Sci. 2019 Aug;36(4):348-353. doi: 10.2108/zs180203.
The valenciniid heteronemertean (Delle Chiaje, 1825) was originally described from Naples, Italy, and shows a circumglobal distribution from tropical to temperate seas in both hemispheres. To investigate its reproductive biology, we performed intermittent year-round sampling from 2014 to 2018 in Misaki on the Pacific coast of Honshu, Japan. Of the 40 specimens obtained, 11 were males, while 29 were immature. No female specimen was confirmed during the sampling period. We additionally observed that is fissiparous. A male individual in captivity reproduced asexually by spontaneous posterior fragmentation, an ability that is described here for the first time among Valenciniidae. Autotomy occurred every 2-10 days, with each of the tail fragments having undergone anterior regeneration, which took about 24-36 days before completion of internal organs, such as ocelli, cerebral organs, brain, alimentary canal, rhynchocoel, and proboscis. A review of the literature suggests that the species was absent in the Misaki region 120 years ago. We assume a recent settlement of a male founder, which has putatively reproduced asexually to yield a clonal, unisexual population in Misaki.
瓦伦西尼异纽虫（Delle Chiaje，1825年）最初是在意大利那不勒斯被描述的，在两个半球的热带到温带海域呈环球分布。为了研究其生殖生物学，我们于2014年至2018年在日本本州岛太平洋沿岸的三崎进行了全年间歇性采样。在采集到的40个标本中，11个为雄性，29个为未成熟个体。在采样期间未确认到雌性标本。我们还观察到它是裂体生殖的。圈养的一只雄性个体通过自发的后部断裂进行无性繁殖，这种能力在瓦伦西尼科中是首次在此被描述。自切每2 - 10天发生一次，每个尾部片段都经历了前部再生，内部器官（如单眼、脑器官、脑、消化道、吻腔和吻）的完成大约需要24 - 36天。文献回顾表明，120年前三崎地区没有该物种。我们推测最近有一个雄性奠基者定居于此，它可能通过无性繁殖在三崎产生了一个克隆的单性种群。
