Katoh Ko, Iwasaki Masazumi, Hosono Shouhei, Yoritsune Atsushi, Ochiai Masanori, Mizunami Makoto, Nishino Hiroshi
Graduate School of Life Science, Hokkaido University, Sapporo, 060-0810 Japan.
Research Institute for Electronic Science, Hokkaido University, Sapporo, 060-0812 Japan.
Zoological Lett. 2017 Mar 13;3:3. doi: 10.1186/s40851-017-0063-x. eCollection 2017.
Facultative parthenogenesis, seen in many animal phyla, is a reproductive strategy in which females are able to generate offspring when mating partners are unavailable. In some subsocial and eusocial insects, parthenogenesis is often more prevalent than sexual reproduction. However, little is known about how social cooperation is linked to the promotion of parthenogenesis. The domiciliary cockroach is well-suited to addressing this issue as this species belongs to the superfamily Blattoidea, which diverged into eusocial termites and shows facultative parthenogenesis.
We studied environmental factors that influence asexual production of ootheca using behavioral assays in . When more than three virgin females immediately after the imaginal molt were kept together in a small sealed container, they tended to produce egg cases (oothecae) via parthenogenesis earlier than did isolated females, resulting in apparent synchronization of ootheca production, even among females housed in different containers. In contrast, virgin females housed with genitalia-ablated males or group-housed females with antennae ablated did not significantly promote ootheca production compared to isolated females. Daily addition of the primary sex pheromone component to the container did not promote ootheca production in isolated females. Another line of study showed that grouped females make parthenogenesis more sustainable than previously known; a founder colony of 15 virgin females was sufficient to produce female progeny for a period of more than three years.
Group-housed females promote and stabilize asexual ootheca production compared to isolated females, and that this promotion is triggered by female-specific chemosensory signals (other than sex pheromone) primarily detected by antennae. Promotion of ootheca production between females is likely to be an early stage of social cooperation, reminiscent of the foundation and maintenance of a colony by female pairs in the eusocial termite .
兼性孤雌生殖在许多动物门类中都有出现，这是一种生殖策略，即当没有交配对象时，雌性能够产生后代。在一些亚社会性和社会性昆虫中，孤雌生殖往往比有性生殖更为普遍。然而，关于社会合作如何与孤雌生殖的促进相关联，我们知之甚少。家栖蟑螂非常适合解决这个问题，因为该物种属于蜚蠊总科，而蜚蠊总科分化出了社会性白蚁，并且表现出兼性孤雌生殖。
我们通过行为实验研究了影响卵鞘无性生产的环境因素。当羽化后立即将三只以上的处女雌虫放在一个小密封容器中饲养时，它们比单独饲养的雌虫更早地倾向于通过孤雌生殖产生卵鞘，从而导致卵鞘生产明显同步，即使是在不同容器中饲养的雌虫之间也是如此。相比之下，与生殖器被切除的雄虫一起饲养的处女雌虫或触角被切除的群居雌虫与单独饲养的雌虫相比，并没有显著促进卵鞘的生产。每天向容器中添加主要性信息素成分并没有促进单独饲养的雌虫产生卵鞘。另一项研究表明，群居雌虫使孤雌生殖比以前认为的更具可持续性；一个由15只处女雌虫组成的创始群体足以在三年多的时间里产生雌性后代。
与单独饲养的雌虫相比，群居雌虫促进并稳定了无性卵鞘的生产，并且这种促进是由主要通过触角检测到的雌性特异性化学感应信号（而非性信息素）触发的。雌虫之间卵鞘生产的促进可能是社会合作的早期阶段，这让人想起社会性白蚁中雌虫对群体的建立和维持。
