(Image via beachsafe.org)
Staff Writer: Emma Bowser
Email: ebowser@umassd.edu
Recent research has led scientists to claim that male blue-lined octopuses (Hapalochlaena fasciata) use venom to immobilize females during and after sex to avoid being eaten.
Female blue-lined octopuses, which are twice the size of males, have been consistently documented eating the males that they had sex with. This isn’t unusual behavior for octopuses, but other species of octopus have utilized different methods of avoiding this fate.
Dr. Wen-Sun Chung, a researcher on the species, describes the phenomenon as the following:“Sexual cannibalism is very common in cephalopods. When female blue-lined octopuses lay eggs, they spend roughly six weeks without feeding just looking after the eggs. They really need a lot of energy to get them through that brooding process.”
Thus, the males have developed this strategy in their own self-interest. Prior to mating, the male will inject some of its venom into the back of the female’s head where the aorta is.
This doesn’t seem to have any permanent effects, but it does cause the female to stop moving and appear to be unconscious. Their bodies took paler than usual, they breathe more slowly, and their pupils stop responding to light.
Describing the process, Smithsonian author Sarah Kuta explains, “Afterward, the females went about the rest of the day eating and behaving normally—with the addition of one or two swollen lumps near their aorta, the scientists noted. And for roughly three days after copulation, females had an open wound on their aorta from the males’ bites. All the females proceeded to lay eggs 3 to 29 days after mating.”
Scientists say that these males are really good at what they do because both the size of the dose and the location are very important. If the males were unable to give the females the correct dose, they might not be able to sedate the female, or the female might die of an overdose.
Furthermore, if they don’t bite the aorta, then the venom won’t affect the female, and she won’t be sedated long enough.
No octopus venom overdoses have been observed during these experiments or in the wild. However, there was a case when one of the males missed the aorta, and the female woke up too soon.
Their venom is a type of neurotoxin called tetrodotoxin (TTX). The octopuses have a symbiotic relationship with a specific species of bacteria that help them produce it in their salivary glands.
When they bite something, the venom in the saliva is then injected into the octopus’s target.
One of the theories behind why the males use their venom is the fact that the males have larger glands than the females. Male glands are typically three times the size of those of the females.
However, the fact that the males bother to use their venom on the females is a little strange because this species only mates once in their lifetime. The males die after having sex, and the females die after the larvae hatch.
Some scientists think that it’s because the females get very angry whenever a male approaches them, and the males tend to approach the females repeatedly.