A (2)

无性虫或纯裂生涡虫Dugesia ryukyuensis的OH菌株会继续发育雌雄同体的生殖器官，如果它们与纯卵生涡虫bdelloephala brunnea的性成熟虫一起喂养，它们最终会进行有性繁殖，而不是无性繁殖，即裂变。这表明性成熟的蠕虫具有一种性致化物质。完全性致化的蠕虫不再需要以有性蠕虫为食来维持其性。在这里，我们证明了性化的蠕虫产生足够的自己的性化物质，类似于b brunnea所含的物质。如果对有性化的蠕虫进行手术切除，有性器官的碎片再生为有性，而没有性器官的碎片，即头部碎片再生为无性状态。性化蠕虫的无性再生体也通过喂食褐螺旋体而完全性化。此外，据报道，性成熟蠕虫的头部区域缺乏完全性化所必需的性化物质（Sakurai, 1981）。这些结果表明，没有性器官的碎片缺乏足够数量的假定的性化物质，性是由性化虫体内所含的性化物质维持的。

Asexual worms or an exclusively fissiparous strain (the OH strain) of the planarian Dugesia ryukyuensis keep developing hermaphroditic reproductive organs and eventually undergo sexual reproduction instead of asexual reproduction, namely fission, if they are fed with sexually mature worms of an exclusively oviparous planarian, Bdellocephala brunnea, suggesting that the sexually mature worms has a sexualizing substance(s) The fully sexualized worms no longer need the feeding on sexual worms to maintain the sexuality. Here, we demonstrate that the sexualized worms produce enough of their own sexualizing substance similar to that contained in B. brunnea. In case of surgical ablation of the sexualized worms, the fragments with sexual organs regenerate to become sexual, while those without sexual organs, namely head fragments, regenerate to return to the asexual state. The asexual regenerants from the sexualized worms are also fully sexualized by being fed with B. brunnea. Additionally, it was reported that head region in sexually mature worms lacks the putative sexualizing substance necessary fir complete sexualization (Sakurai, 1981). These results suggest that the fragments without sexual organ lack enough of an amount of the putative sexualizing substance and the sexuality is maintained by the sexualizing substance contained in the sexualized worms.