Sobre la conducta sexual del pulpo -Mark Norman- Bizarre Octopus Sex-

Published Sunday, September 10, 2006 by Spyder | E-mail this post

Es la transcripción de una entrevista que mantienen Mark Norman y el presentador Robyn Williams en el el programa The Science Show en la cadena ABC, respecto a ese pequeño gran pulpo.

Bizarre Octopus Sex

This transcript was typed from a recording of the program. The ABC cannot guarantee its complete accuracy because of the possibility of mishearing and occasional difficulty in identifying speakers.

Mark Norman: These are the very brittle shells that wash up on southern Australian shores mainly and it's produced by a fairly normal looking octopus that lives in this funny looking shell. The female gets to about the size of a football and she swims around in open ocean grabbing small shrimps and fish. The male is about the size of a jelly bean, has no shell, mainly travels by hollowing out tubular jelly fish and driving this little jelly fish like a jet scooter out of The Jetsons, using jet propulsion to drive this little tube along, and he seems to spend his life hunting around hoping to bump into a female. And these animals very rarely come near shore; sometimes they strand and die and people find hundreds and hundreds of shells washed up but we managed to get in the water with some live ones in Port Phillip Bay late last year and they are the fastest, most spectacular animals. It's like driving around with little alien robots on jet propulsion, they can swim faster than we can so we were sort of swimming like crazy to keep up with them. They have a row of sharp spines on the edge of the shells and when you get close they turn around and ram you full speed with the spines on the front of shell, which scratched hell out of all our video camera lenses.

Robyn Williams: I can imagine yes.

Mark Norman: But this is sort of, rare footage; nobody's really filmed these things live before so it was a fantastic opportunity. We also found that they're using the shell as buoyancy control: they're bobbing to the surface, taking a gulp of air in the shell and then moderating the amount of air in it to control their level in the water and then jetting away, so it was just a very rare opportunity for us to come across such a strange animal.

Robyn Williams: Isn't that interesting, Mark because I always thought the Nautilus lived very, very deep down?

Mark Norman: Well, there's the true Nautilus, the chambered Nautilus, it's the really primitive one, and those animals used to dominate our oceans. They got to three and a half metres in diameter, these monsters sort of mini vans with squid heads stuck in the front; they're the really primitive ones, and then at the opposite stream of, or radiation of these animals you come across a fairly normal looking octopus swimming around in a convergent -shaped shell, as these pelagic ocean travellers, and these are sort of blue water drifters, they hang out in the middle of the blue water oceans, in surface waters, feeding on shrimp and fish.

Robyn Williams: And what you're saying before is that the male is so very much smaller than the female.

Mark Norman: He's tiny: so she's the size of a football, he's the size of a jellybean. When he finally bumps into a female he has this sort of, kamikaze sex system where he breaks off a special arm full of sperm, he dies and the arm independently crawls into the female's gill cavity where it hangs and is probably stored alive for anything up to months.

Robyn Williams: Do you mean she's swimming around with this arm.?

Mark Norman: With live arms, like things from the crypt, in her gill cavities and they've found females in trawl nets with six male arms wrapped around their gills, and she must wait until her eggs are mature and then feel round in her pockets for these sort of, live tetra packs of sperm, tear the caps off them and sort of sprinkle them on her eggs as she's doing her egg laying into the inside of the shell; so they hang the eggs from the inside of a shell.

Robyn Williams: Clearly she knows the arms are there?

Mark Norman: Well, who knows? I don't know actually what's going on but they'd actually be like little tiny tickling devices in the background, so - very, very strange animals. Some friends had one animal in an aquarium for three weeks, a female; she finally died. The male arm crawled out of the female - there's no male in sight - this live arm is crawling around the aquarium three weeks at least since it was separated from the male. So how the hell does this arm stay alive, how's it fed oxygen, fed nutrition? It's a real puzzle and we're trying to get a handle on that.

Robyn Williams: I can imagine. But I would have thought a rather neater way of doing it is for the male to give up its 'arm', if you like, and the sexual content thereof and then grow another one.

Mark Norman: I know, but there's been males caught quite frequently in trawl nets, there's never been a male found with a regenerating arm. The arm is half the male's body weight and their reproductive system only produces one sperm package and that sperm package gets inserted into the arm and then it's all over. So it's a sort of different form of that massive size dimorphism you get in things like deep sea angler fish, where they get six little parasitic males all sucking off blood vessels and just producing sperm. This is sort of a short-lived kamikaze version instead.

Robyn Williams: How amazing. Yes, well that discrepancy - the football to the jellybean - how extreme does that size difference get?

Mark Norman: Well, we were pretty blown away by that and then also recently we had a very rare encounter. We came across the first live male blanket octopus, which is a related family to the the paper nautiluses, and again we found a little jelly bean shaped guy swimming around and we took some photographs of him. We weighed him and he was .23 of a gram.

Robyn Williams: That's tiny. The one I'm looking at now is just gorgeous.

Mark Norman: He's a beautiful little orange guy with these deep webs on the arms with iridescent little orange spots all over the webbing and this pouch that has the modified arm developing in it ready to break off and give to the female. He was fully mature at .23 of a gram. We have measurements on females that they get up to 2 metres long and 10 kilograms, so she's 40,000 times heavier than the male is. So you're dealing with this sort of jumbo jet with this annoying sparrow kind of pecking at its tail and just after we'd found this male we got an email from the Azores in the Atlantic Ocean, where they'd come across several live females for the first time and photographed them underwater and that's one of the photographs we've got there as well. They found one of them had a live male arm crawling his way up the length of the arms towards the female's gill cavities. So it had been a very recent mating. The arm was trying to get somewhere safe where it doesn't get blown off in the current.

Robyn Williams: How does she notice she's been mated then?

Mark Norman: Well, maybe she doesn't, who knows? I mean, she may just come to the stage of laying eggs again and go, Do I have any of those sperms packets on me. And again, the multiple arms full of sperm in females that have been caught in trawls as well, so very, very strange life cycles. But it wasn't till we actually got the photographs back and started developing that we realised that one of the photographs is the first live photograph anywhere in the world of the really weird defence behaviour of these little jelly bean males. These animals must be so vulnerable out in open ocean where they could be eaten by any passing tuna or fish or trevally, or barracuda or anything.

Robyn Williams: Yes, he looks most apprehensive: that great big eye. Describe what we're looking at here.

Mark Norman: Well, we've got a little round bulbous body which is probably close to a jelly bean, a pair of large eyes staring out from that and then arms about the same length as the jelly bean, which in this photograph he's pulled back over his head - and this was as we approached the animal, it kept pulling his arms over his head. When we got the closeup photographs back and developed them we thought that we'd actually got some muck tangled on the suckers and when we looked up close they're actually little short segments of jelly fish tentacles. And it turns out that this little guy is carrying around live tentacles from jelly fish that he's removed from jelly fish and is holding like little clear pieces of rice vermicelli in his suckers as a defence. And so an animal the size of a jelly bean is packing a jelly fish punch which is probably enough to knock out a 30cm tuna that comes along and bites it, because the stinging power of some of some of these jelly fish is incredibly strong, as we've seen by recent stings and deaths associated with the Irukandji jellyfish.

Robyn Williams: Well this is quite interesting, because I've heard of that kind of use of other creatures' weaponry before, and the trick is to absorb them into your own body without setting off the mechanism.

Mark Norman: Yes, there's some little open ocean sea slugs that do it and some of the sea slugs that eat poisonous sponges and things like that, but this goes a step further. Animals like boxer crabs put live anemones on their claws and then, kind of aim the claws at whoever is having a go at them. This doesn't take the whole jelly fish; he's regularly farming fresh clean pieces of armoury from passing jelly fish and it's quite possible that these guys hitchhike on the back of jelly fish like their paper nautilus relatives do. We've got this photo from the Andeman Sea, of one of the small paper nautiluses hitchhiking on the back of a jelly fish. Like the photographer who took the photos said it took him an hour to get the photo because every time he tried to take a snap the little paper nautilus squirted jets of water to turn the jellyfish's tentacles towards the diver, and in the end he had to use two divers to even get the photograph. So it looks like this group of animals, the paper nautiluses and the blanket octopuses, have probably long associations with jelly fish and have developed immunity to their stinging cells much like the anemone fish, the clown fish, that live in the big anemones.

Robyn Williams: Well back to this little fellow's sex life. I've heard about intimidation when you've got a big beautiful woman who is just completely outclassing the little boy, but how did this come to be? Could you imagine that?

Mark Norman: Well it's something that we've been speculating on and we're writing this work up at the moment. One possibility is that both of the sexes found refuge by being small enough to use these jellyfish defences, and the females have been found from trawl captured animals to have jelly fish tentacles up to the size of 7 cms. When the females are bigger than 7 cms they never find jellyfish tentacles. So it's possible that that small size works for using jelly fishes defence; anything bigger you start to lose it. Now a male can produce tones of sperm and be that size but the female, to produce hundreds of thousands of eggs to pour out into the water to give their young a chance of survival, they need to be big body size. So we have no idea what defences the females take over once they stop doing the jellyfish things but there may have been a refuge for the male to stay hiding in that jellyfish defence world while the female got bigger and bigger and found other means of defence or other decoys.

Robyn Williams: Well obviously they can still reproduce, however tiny he is compared to her.

Mark Norman: Yes and there's a lot of parallels to things like barnacles, where the parasitic male of the female barnacle can be absolutely microscopic just living on the lip of the barnacle and all he has to do is produce sperm and that takes a fairly low energy input compared with females producing hundreds of thousands of eggs.

Robyn Williams: I suppose if it was in human society it would have a tiny testicle on tiny legs.

Mark Norman: Chasing you around a crowd or along the freeways or something and hoping to stick something on your boot that will eventually crawl to the necessary route.

Robyn Williams: Or maybe just kept in the cupboard until it's needed.

Mark Norman: A handy little purse of them on a hook, or something like that.

Robyn Williams: It would have some advantages.

Mark Norman: Yes, but I'm not advocating that for us.

Robyn Williams: Thank you.

Mark Norman: No worries.

Guests Mark Norman

Research Fellow Department of Zoology Melbourne

Universitymailto:mnorman@unimelb.edu.au

Labels: Comportamiento