Male mantises are eaten by much larger females during mating. It is a heartbreaking sacrifice, giving their own bodies for the sake of their offspring. However, not all creatures in nature accept their fate willingly. The male blue-lined octopus (scientific name: Hapalochlaena fasciata) rejected its fate of having to sacrifice itself for its offspring.
Justin Marshall, a chair professor at the Queensland Brain Institute in Australia, noted on the 10th (local time) that "male blue-linged octopuses subdue females using a toxin called tetrodotoxin to avoid being eaten during mating." The research results were published in the international academic journal Current Biology that day.
◇Subduing females with venom during mating
In octopus mating, the male inserts an arm that acts as a reproductive organ into the female's reproductive organ to transfer sperm. The male reproductive arm is distinguished by the absence of suckers at the tip. Mating in octopuses occurs with the sexes completely entwined, posing a high risk for smaller males of being eaten by females.
The blue-lined octopus was different. Researchers at the Queensland University observed six pairs of mating, where all males completed sperm transfer and left without injury. This was thanks to using tetrodotoxin as a sedative. Although the blue-ringed octopus is only the size of a palm, it possesses a deadly toxin that can kill humans.
The researchers observed that the male bit into the aorta of the female octopus during mating. As a result, the female's skin turned pale and her breathing slowed. Even when the researchers shone a light in the female's eyes, her pupils did not constrict. The female was paralyzed by the venom. The octopus is immune to its own venom, so it does not die but is paralyzed for a short time. About an hour later, as the toxin wore off, the female pushed the male away.
The researchers found that the males' venom glands were about three times larger than those of females. This is because venom must be used not only for hunting but also to calm the females. It can also be seen as an arms race between sexes during the evolutionary process. The first author of the paper, Wen-Sung Chung, stated that "the males likely needed larger venom glands to produce more venom to overcome the females' resistance."
◇ Male mantises survive by fighting
Most octopuses sacrifice their whole bodies for their offspring, just like spiders or mantises. Both mate only once. The smaller male is eaten by the female, thus providing nutrients for their own offspring. After laying eggs, the female does not eat and dedicates the rest of her life to caring for and protecting the young.
However, the researchers could not clarify why male blue-lined octopuses reject their fate of being eaten by females, even using venom for this purpose. In fact, even if males are not eaten by females after mating, they do not survive long. Understanding why males need to survive may help explain why they calm females with venom.
In some mantises, males overpower females and survive after mating. Researchers at the University of Auckland in New Zealand reported in 2021 that males of the cannibalistic species, the Springbok mantis (Miomantis caffra), survive by fighting with females.
Generally, male mantises are approached by females but 60% are eaten before mating can occur. Male Springbok mantises increased their chances of successful mating by overpowering females in combat. In fights, 7% resulted in a draw, while 35% were won by females, leading to the males being eaten before mating. In 58%, males emerged victorious. In this case, 67% led to mating, and half of those survived. These are desperate loves seeking to spread their offspring by any means.
References
Current Biology (2025), DOI: https://doi.org/10.1016/j.cub.2025.01.027
Biology Letters (2021), DOI: https://doi.org/10.1098/rsbl.2020.0811