Scientists observed male blue-lined octopuses injecting tetrodotoxin into females, which rendered them immobile for mating

Now, researchers studying the octopuses have learned that not only do male blue-lined octopuses use their venom against enemies, but also against members of their own species — cannibalistic females.

Male blue-lined octopuses inject females with venom during mating to avoid being eaten by their partners, observations suggest 1. Blue-lined octopuses ( Hapalochlaena fasciata) have paralysing venom that can kill a human. Females also have large appetites and are twice the size of males, making sex a risky business.

"Mating ended when the females regained control of their arms and pushed the males off," the researchers noted.