AYESHA RASCOE, HOST:
The love life of a male blue-lined octopus is tough. Like praying mantises and widow spiders, a female blue-lined octopus will often kill and eat the male after mating. It's just a circle of life for these creatures. The smaller males provide sustenance to the females as they lay and look after their eggs. But new research from the University of Queensland in Australia suggests some males have figured out a way to turn a final-night stand into more of a one-night stand (laughter). Fabio Cortesi is one of the researchers on the project, and he joins us now. Welcome to the program.
FABIO CORTESI: Thank you very much for having me.
RASCOE: How great is a female blue-lined octopus' need for energy after mating?
CORTESI: So after mating, they just stay for a while, and then they lay their eggs after about something like 40 days. And once they've laid their egg, they will look after their eggs. They will look after their brood, and they will not feed during that time. So they need to feed before they lay the eggs as much as they can so that they can store the energy for the brooding afterwards, which takes a couple of months. So very, very hungry.
RASCOE: And these creatures, these octopuses, they're venomous. Is that the case?
CORTESI: They use tetrodotoxin, which is TTX, one of the most potent natural venoms known out there. It can kill humans - very small amount.
RASCOE: Oh, wow. So tell me about the study. What did you do, and what did you discover?
CORTESI: Yeah, so what we do is we look at the brain of these animals. We're interested in their neurobiology. And so as part of this study, we got a bunch of animals. We got them in the lab, and we - it was during the mating season. So we observed that the males were actually trying to copulate with the females. And the way they were doing that was by mounting them, and then we noticed that the female essentially pales up and stops all movement after about eight to 10 minutes. And this lasts for about an hour. And then she wakes up and essentially usually is very, very angry and throws the male off her back. And we found that the venom gland of the males is about three times the size of the one of the females. And that didn't really make sense to us because, you know, they both feed on the same kind of prey. They don't really need more. The male is usually a lot smaller than the female as well. So we found that they use this extra venom actually to essentially envenomate the female during copulation.
RASCOE: Are these male octopuses that you observed kind of learning from maybe their friends' past mistakes and going, I don't want to go out like that?
CORTESI: (Laughter) Very good question. So it's the first time that envenomation with TTX has been observed in the animal kingdom. In octopuses, it's the case that in most species, the females tend to try and feed on the males. And so they've evolved different mechanisms to avoid that. One of them is to have a long - they use a mating arm. They don't actually have a penis. They use a mating arm to transform the sperm packets. And so, in some species, the arm, the mating arm is very long, and they keep the female at bay. But in this species, they bite the female, and they don't learn this from any other animals because after mating is over, after the mating season is over, these octopuses lay their eggs, and then they essentially die, and the males also die.
RASCOE: Do some of the male blue-lined octopuses get eaten or have they evolved so that doesn't happen because they - all of the males are doing this venom trick or this venom bite?
CORTESI: Yeah, very good question. So it looks like this has evolved as an [inaudible]. As the female becomes bigger and bigger than the male, the threat of getting eaten obviously increases. But the males still need to mate. The species needs to survive. As far as we know, they don't learn by watching other males. They learn essentially by mistakes. So if they don't bite at the correct spot - they usually bite close to the aorta. If they miss that spot, then the female usually wakes up much earlier, and they might lose an arm or two during the mating.
RASCOE: Oh.
CORTESI: And so the next time...
RASCOE: OK.
CORTESI: The next time they try and mate, they will get much more precise in their approach.
RASCOE: (Laughter) Precise. They're like, OK, that didn't work out. OK, OK.
CORTESI: Exactly.
RASCOE: Yeah. Is there anything else that we as humans can learn from a discovery like this?
CORTESI: Yeah, we can. So TTX, as I said, is a very potent nerve toxin, essentially. So it paralyzes your nerves. The way it works is that it stops the communication between your nerve cells. And so usually, if anything else gets envenomated, it dies pretty quickly of a heart failure because the heart stops beating. And so the other thing it does, obviously, is because it numbs the nerve it might be used in some sort of pain medication in the future. Now, these octopuses obviously have evolved to survive this. I mean, the female - she cannot move for about an hour, but she doesn't die. We didn't lose one animal in the whole study. So they can deal with it. We know how they do it at the molecular level, more or less, but we don't really understand how it works at the higher-up nerve system level, I guess. And so that's one area of great interest for us, for sure.
RASCOE: That's Fabio Cortesi of the University of Queensland in Australia. Thank you so much for speaking with us.
CORTESI: You're welcome. Thank you for having me.
(SOUNDBITE OF SONG, "OCTOPUS'S GARDEN")
THE BEATLES: (Singing) I'd like to be under the sea in an octopus' garden in the shade. Transcript provided by NPR, Copyright NPR.
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