Female American cockroaches (the big ones that people like to euphemize as “waterbugs”) can reproduce without males, according to a study out of Japan’s Hokkaido University. The study also revealed that this process is expedited within groups of females who synchronize production of egg cases. Sounds like feminism in nature (and under your sink) to me!
The study, which was published earlier this month in Zoological Letters and details various observations from experiments in which multiple populations of cockroaches were raised, reports on one sample population’s parthenogenesis (asexual spawning), a phenomenon that has also been observed in other insects, as well as some species of scorpions, lizards, and the misunderstood gentle giants among us, sharks. Says the team from Hokkaido U:
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.
Additionally, “a founder colony of 15 virgin females was sufficient to produce female progeny for a period of more than three years.” Even when the’ve looked massive and, frankly, muscular (for insects), cockroaches have never struck me as positively Amazonian... until now.
The study also includes an interesting contrast of harmonious female cockroach behavior versus the barbarism witnessed in their male counterparts:
In pre-social, domiciliary cockroaches, females of the same kin tend to aggregate in the same colony, whereas males leave the colony to avoid inbreeding. Our behavioral observations are consistent with this finding; unmated females housed in the same container huddle close together with almost no fighting, whereas paired unmated males often fight until the antennae of both individuals are amputated (Nishino, personal observation). Thus, recognition of other virgin females and subsequent promotion of ootheca [egg case] production might be the early stage of social cooperation that drives more prevalent parthenogenesis. This cooperative behavior is possibly succeeded by eusocial termites, five Reticulitermes species that found the first colony by female-female cooperation.
An all-female colony of 15 that started in December 2013 had grown to a colony of 300 by February 2017. The colony remains all female because parthenogenesis in this species yields offspring that is entirely female. The Hokkaido team, though, found that the mean number of nymphs hatched from parthenogenesis versus sexual reproduction was lower, suggesting “parthenogenetic eggs show lower fitness than sexually produced eggs.” Regardless it seems like not having males anywhere in their living space is really working for the female American cockroach.