As It Happens

'They're coming!': Mutant all-female crayfish are cloning themselves at an incredible rate

The all-female marbled crayfish reproduces through cloning — and although it is a relatively new species, there are already huge populations around the world.
The marbled crayfish is a highly invasive species that reproduces by cloning itself. (Submitted by Wolfgang Stein)

Story transcript

It may look like nothing but a humble crawdaddy, but "crawmommy" would be a more appropriate nickname.

The all-female marbled crayfish reproduces through self-cloning — and although it is a relatively new species, there are already huge populations around the world, according to a new study published in Nature Ecology and Evolution.

Wolfgang Stein, a neurophysiologist at Illinois State University and one of the researchers on the study, spoke to As It Happens host Carol Off about the invasive crayfish and what we can learn from its unique genetic makeup. 

Here is part of that conversation.

What have you learned about these marbled crayfish in this new study?

We sequenced the genome of this particular type of crayfish and the really interesting finding is that they are essentially all clones of one another. So their genomes are essentially exactly the same, no matter which individual you take.

We also found that they reproduce asexually, which means they don't need any partners. The whole species is essentially female. There are no males, but they still reproduce. I think that's quite interesting. 

Wolfgang Stein is an associate professor of neurophysiology at Illinois State University. (Submitted by Wolfgang Stein)

It's very interesting. Are there a lot of them?

There are quite a bit of them. The interesting thing that we found is also that this whole species occurred, or came into place, about 25 to 30 years ago. It didn't exist before that.

There was one animal that had an anomaly which allowed it to reproduce without males. And so from that one animal, the whole population now that we can find worldwide — in Japan, in Madagascar, in Europe, and also in the U.S. — that's where all of these animals stem from.

So wait a second, was there an original family? I mean, was there a male and female that had some kids and this is one of them? And that one produced all the rest?

Yes, that's exactly what happened.

The parents were called slough crayfish. Those are a crayfish that live in Georgia, in Florida.

And apparently, a couple of them mated and then one of the daughters inherited an additional set of chromosomes, and so they now have three sets instead of two. And that one daughter started to reproduce without males and it gave rise to the whole population we see now. 

All marbled crayfish are female and share the same genomes. (Submitted by Wolfgang Stein)

Good heavens. How do they get around? How did they spread so far and wide?

It's really pet trade. It's humans that carry them around and sell them. That's actually how the first animal made it to Europe. We don't know exactly who brought it over, but we know who bought that one animal that came to Germany in the mid '90s or so. And from that one animal, all the offspring were sold in pet trade and they are now sold in all kinds of countries. That's how they spread.

So they don't travel by themselves, but if you have one animal, essentially, three months later, you will have 200 or 300 offspring that are again clones of the mother and they will also reproduce within three or four months and have more babies. 

To give you an idea, in that particular study, we looked at Madagascar. The first time this particular species of crayfish was found in Madagascar was around 2007. And at that time, they occupied an area that was about half the size of Rhode Island. Now, in 2017, they occupy the area the size of Ohio. That's a hundred-fold increase in just a decade.

They're coming.

Yes, they're coming!

Well, maybe you can add a food expert to your team and see if you can come up with some recipes?

That would be nice. Actually, commercially, that is an interesting species as well because they are very easy to raise and I don't see why you wouldn't be able to eat them.

Lots of protein.

Lots of protein, exactly.

This interview transcript has been edited for length and clarity. For more on this story, listen to our full interview with Wolfgang Stein.


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