�����鶹��Ƶ

During mating, some male octopuses inject females with their potent venom to paralyse them – and avoid being eaten by their mates.

Typically, animals use venom to kill prey or defend themselves from predators. Some species of pufferfish, for example, produce one of nature’s most potent venoms, tetrodotoxin, as a defence mechanism. Several blue-ringed octopus species use tetrodotoxin as a powerful weapon to quickly immobilise and kill their prey.

Now, in a scientific first, from the University of Queensland, Australia, and his colleagues have found that one of these species, the blue-lined octopus (Hapalochlaena fasciata), uses this same toxin during reproduction.

Using behavioural experiments, the team observed how the male mounts the female and lands a targeted bite near her aorta to inject tetrodotoxin. The venom rapidly causes the female’s breathing to slow and her body to turn pale.

While it is deadly to most animals, the octopuses have evolved a natural resistance to their own venom; it does not kill the female, but renders her immobile. This ensures that the male can successfully mate and avoid the risk of cannibalism by the much larger female – a common occurrence in many octopus species.

“We also found the males’ venom glands were much larger and heavier than the females’, likely owing to the males’ need to produce larger volumes of venom to overcome the females’ innate resistance,” says Chung.

“This is a great example of a co-evolutionary arms race between sexes, where a cannibalising large female is counteracted using venom in males,” says at National Tsing Hua University in Taiwan, who was not involved in the study.