A (2)

无性繁殖的蠕虫或龙虾的一种完全裂生的品系(OH品系)继续发育两性生殖器官，最终进行有性繁殖，而不是无性繁殖，即分裂，如果它们被喂养一种完全卵生的脊椎动物Bdellocephala brunnea的性成熟蠕虫，这意味着性成熟蠕虫具有性化性物质(S)完全性性化的蠕虫不再需要捕食有性蠕虫来维持性行为。在这里，我们证明了性化的蠕虫产生了足够的性物质，类似于布氏杆菌所含的物质。在手术切除性化的蠕虫的情况下，有性器官的碎片再生成为有性的，而那些没有性器官的碎片，即头部碎片，再生回到无性状态。来自性性化的蠕虫的无性再生体也通过喂食布氏杆菌而完全性别化。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假定的性感化物质(Sakurai，1981)。这些结果表明，没有性器官的碎片缺乏足够数量的推定的性化物质，性行为是由性化后的蠕虫中包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.