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The marbled crayfish is a mutant species that clones itself (nytimes.com)
265 points by sohkamyung on Feb 6, 2018 | hide | past | web | favorite | 60 comments

If I understand this correctly, asexual reproduction in plants is called apomixis[0] and the dandelions and blackberries have been doing it for millions of years.

In animals it is called parthenogenesis and happens in lizards, snakes, birds and sharks[1]. All of them have been around quite some time on earth, also.

What helped these species to be so resilient to a devastating infection when other animals that reproduce sexually (Central American frogs, North American bats) are being wiped away so badly by fungal infections?

[0] https://en.wikipedia.org/wiki/Apomixis

[1] https://en.wikipedia.org/wiki/Parthenogenesis#Natural_occurr...

It could literally just be time and luck.

We started mass production (cloning) of cavendish bananas around the the 1900s, and REALLY started mass production (cloning) in the 1950s, we only started seeing strains of banana blight effect it in the last few decades. Obviously there are all sorts of differences between these cases, but it's probably worth thinking about a bit.

Oh, also it looks like most animals capable of parthenogenesis can also under go sexual reproduction, helping them hedge against certain types of threats.

Also remember that we're looking at animal population on human generation timescales. One might say that a species with a population of millions being wiped out to a population of thousands (that are fungal resistant) over a time scale of 60 years as a 'disaster'. It in our life time it probably is, cause our activities would probably completely fuck over whatever is left. But in the absense of our activity, those thousands or so could still form a viable population and if they still have a good ecological niche to occupy, could easily within a few hundred/thousand years regain their original population. And we'd be all completely blind to that, cause that's not how we tend to think.

> we only started seeing strains of banana blight effect it in the last few decades. ... it's probably worth thinking about a bit.

It was likely an oversight to not mention why we started to clone the Cavendish.

Panama disease devastated the also cloned Gros Michel cultivar over 60 years ago. That's why, today, we eat a different banana than those who came before us.

>What helped these species to be so resilient to a devastating infection when other animals

Well for starters asexual reproduction is an option for them, not the sole means of reproduction.

Secondly, diseases and catastrophes strike all sorts of critters and sometimes no amount of genetic variation will save them. For example you mention snakes and their resilience: http://www.bbc.com/news/science-environment-42428528

Thirdly, snakes, lizards, sharks, make up a huge number of species and genetic variability with global distribution. That provides some protection. And for most of history global pandemics were probably less common or were slow enough that it didn't happen at once everywhere. And if enough individuals survive for the species to recover, then that's that.

Fourth, sexual reproduction isn't a guarantee of immunity to disease, it's a survival strategy to help increase the odds of surviving as a species or having individuals with immunity because of all the possible combinations of genes being tried. For example, AIDS (without treatment) is lethal for most of the human population. But there are a few Scandinavian groups that have partial or full immunity, something like less than 1% of the total human population. That's what sexual reproduction gets us as a species.

Low genetic diversity can have unexpected benefits; within Argentine ants it has given rise to a global supercolony, because the pheromones of different hives have become indistinguishable.


Neat. Ants really are one of the most interesting species. (Or, if not species, whatever the appropriate taxonomical term is.)

IIRC some of those animals that can reproduce asexually don't necessarily do it exclusively (sharks).

>What helped these species to be so resilient to a devastating infection when other animals that reproduce sexually (Central American frogs, North American bats) are being wiped away so badly by fungal infections?

At least some plants have genes that randomise genetic code if I recall my high school biology well. I also read that polyploid plants have something to randomly shuffle chromosome sets.

Quite alike a stack randomisation it is

Asexual reproduction gives an individual (in the genetic sense) more time to reproduce while also acting as something of a checksum on the genome as a whole. Survival during disease outbreaks would certainly be increased if one didn't need to balance infection versus dying of old age against somewhat more genetically advantageous sexual reproduction. It's an interesting delay tactic.

> All of them have been around quite some time on earth, also.

Asexual species have been around for "quite some time" by comparison to, say, all of recorded history.

They tend to be very recent on a geological timescale.


> Asexual species have been around for "quite some time" by comparison to, say, all of recorded history. They tend to be very recent on a geological timescale.

Asexual reproduction was there first and predates sexual reproduction by several billion years. Some species then evolved back asexual reproduction, like this marbled crayfish.

Asexual reproduction yes, but GP's point is that asexual species seem much younger, seem to generally speaking not "last" on long timescales.

Which would make sense, if an individual has great fitness they can "boom" extremely rapidly, but then any change in condition or emergence of specialised predator or disease will take down the entire population just as quickly because it has very low variability and flexibility.

Ah, thanks for the clarification. But then all species, asexual or not, are young with regards to geological times. I think the order of magnitude for longest species lifespan is about 10 million years. Is there really a correlation between species lifespan and method of reproduction?

This crayfish evolved 25 years ago. The article cites another study on asexual flea species, where the mutation was 1250 years old. That's two examples and both very far away from 10 million years.

It's «Marmorkrebs» not »Marmokrebs». From Marmor -> Marble. Also, a simple Google/Wikipedia search should have been possible, dear NYT :(


The mistake might have come from this 2010 Scientific American article which uses the wrong spelling in the title.


I've sent a tweet to the author and NYTimes about this. Hopefully they'll correct it.

They did.

>Only 1 in 10,000 species reproduce by clones.

When you see a statistic like that it points to a filtering event in a species. Much like the previous type of banana was clones, once a disease rises up that attacks that type of clone there just isn't the genetic diversity and rate of change to save the species.

I dunno, given the number of bugs alone, a statistic like that strikes me as just numerical drama.

The explanation is found halfway through the article.

> Normal sex cells contain a single copy of each chromosome. But the mutant crayfish sex cell had two.

> Somehow the two sex cells fused and produced a female crayfish embryo with three copies of each chromosome instead of the normal two. Somehow, too, the new crayfish didn’t suffer any deformities as a result of all that extra DNA.

> It grew and thrived. But instead of reproducing sexually, the first marbled crayfish was able to induce her own eggs to start dividing into embryos. The offspring, all females, inherited identical copies of her three sets of chromosomes. They were clones.

> Now that their chromosomes were mismatched with those of slough crayfish, they could no longer produce viable offspring. Male slough crayfish will readily mate with the marbled crayfish, but they never father any of the offspring.

Supposedly they taste good and part of their spread is intentional. See the bottom of this article: https://www.nature.com/articles/d41586-018-01624-y?utm_sourc...

I was thinking about a culinary solution to this problem. They could even be farmed, considering their numerous offspring.

Seems like an ideal protein source for space travel. Even if the genomic monoculture represents a serious starvation hazard.

This is absolutely mind-blowing.

Also, since humans are now very numerous and so good at surviving, makes you wonder if humans could mutate this way too. Makes it seem like you'd just get outright pregnant instead of ovulating, which may be a bummer.

In mammals, epigenetic information is needed from both parents. Its thought that this epigenetic information is kind of a negotiation between the survival/growth traits of male DNA, and the resource strain put on the female during embryonic development and child-rearing. Kind of like a product feature request list being paired down for production delivery.

It looks like there is some evidence, from mice experiments, that epigenetic information could be synthesized to induce asexual reproduction in mammals. I also found a recent gene editing technique to directly edit mice epigenomes, in theory that might be a path to design an asexual mouse, or another asexual mammal.

https://en.wikipedia.org/wiki/Parthenogenesis#Mammals https://en.wikipedia.org/wiki/Genomic_imprinting https://www.sciencedaily.com/releases/2017/12/171207141735.h...

The article ends by explaining why asexual cloning is a bad idea in the long term and how few species exist like this, outside of some relatively new ones, because they lack the evolutionary benefit of sexual adaptation (such as fighting diseases and other evolutionary traits).

I guess technology and modern medicine could counteract that but it's still not ideal in the long-term. Nor would genetic clones create a very interesting society.

It would make a very interesting society.

Mass-produced clothing would fit well. Public schools would not need to worry much about the extremes of ability. Shared mental traits would encourage a high level of trust, but identification difficulty would undermine it. With everybody having the same innate ability and interests, the pay differences between different jobs would be much higher.

> Nor would genetic clones create a very interesting society.

One of the more interesting attempts at creating a human society made up of clones is the James Tiptree, Jr. story, "Houston, Houston, Do You Read?" [1]

[1] https://en.wikipedia.org/wiki/Houston%2C_Houston%2C_Do_You_R...

Theres also an Outer Limits episode of a guy trapped on another planet who self replicates clones of himself. Although I think it does it more through "splitting" than an actual birth cycle. Very freaky episode with lots of "body-horror" as he begins to split.

Could it somehow mutate again in a way that makes it able to reproduce sexually?

Good idea, I was thinking it would be interesting if the species could turn asexuality on and off as conditions required.

Mistranslation: "German Cancer Research Center" should be "German Crabs Research Center"?

"Cancer" is the right English translation in this case - the German original is "Deutsches Krebsforschungszentrum". A center dedicated to studying crustaeceans would probably be called "Krebstiereforschungszentrum" ("Crab-animals" research center).

"Krebs" means either cancer (the diseases) or crabs (the animals). The tumors that early physicians saw reminded them of crabs, so that's what they called them. English forked cancer (Latin word for crabs) to mean the diseases and uses the evolved colloquial word for the animals, but German uses its evolved colloquial word for both. "Krebstiere" is often used to refer to crabs as a group, probably to avoid misunderstandings.

Prof. Dr. Lyko seems to primarily study epigenetics, and it's just coincidence that the animals he's studied here are crabs: http://www.dkfz.de/en/epigenetik/

Just glanced over a german language interview, it's basically the introductory question, "sounds like a bad joke, please explain". Actual cancer researchers, looking for a cloning species to observe environmental influence on gene expression (which seems to be a candidate cause for some kinds of cancer or so). So they basically did it for confirming the availability very big, naturally occurring twin experiment.


One way to get rid of this problem is if they taste good, market them to Asian restaurants.

Right now spicy crawfish boils are fashionable in China, and I'm pretty sure the other East/Southeast Asian countries like crawfish also.

Just like with jellyfish. Chinese people already eat jellyfish, so if there's an infestation of jellyfish in the ocean, figure out a way to eat that species. A billion people can really put a dent in any wild population.

In France they are an invasive species. We are eating it (it can be found on sale everywhere) but it's not very good.

We have been eating crayfish for a long time; indigenous French (or European?) crayfish were delicious but they have been wiped out by this species.

In the UK the native crayfish are already severely threatened by invasive signal crayfish. I'm not sure if we have marble crayfish yet but if they breed that quickly it sounds very bad for the native crayfish - and maybe for the accidentally introduced signal crayfish too.

There are various streams near me where you can go out in summer with a piece of bacon, some string and a box (maybe a net too) and catch signal crayfish. You don't need a permit as they're an invasive species - in fact you're not allowed to put them back if you catch any.

(But do put them back if you catch the native species! The signal crayfish are larger and have big red claws with white flashes which give them their name.)

edit: was writing my now largely redundant post as masklinn posted. I hadn't realised the Marmorkrebs were smaller - does that make them less of a threat? It does say they're already a problem for native species in Madagascar.

I'm off to buy bacon right now! Any particular streams? Slow/fast moving? Mind you, given the temperature it might be more like ice fishing.

It appears I was mistaken and you do need a licence, though it's free. You should also ask the landowner's permission.

I had thought you only needed the licence to set up traps, which I'd rather not myself as there's a risk of catching/injuring/killing other species, particularly native crayfish or otters. Sorry for the inaccurate post. Sadly it's too late to edit it or I'd put strikethrough all over it...

More details about catching (mostly with traps) and licence details below. http://foragedfoods.co.uk/how-to-catch-signal-crayfish/ https://www.gov.uk/guidance/permission-to-trap-crayfish-eels...

To answer your questions, I'd wait until at least spring; I've only been in summer. Not sure about speed or depth (I've seen them in fast shallow streams and in a slower metre-deep river) but they like lots of hiding places like rocks or overhangs.

> We have been eating crayfish for a long time; indigenous French (or European?) crayfish were delicious but they have been wiped out by this species.

AFAIK indigenous european species have mostly been displaced by various american species (mostly spinycheek, signal, and louisiana crawfishes) — and severely hit by diseases those brought[0] — over the course of the 20th century. The marbled crayfish is a recent development.

I don't think the marbled crayfish is great cooking fare, it's pretty small.

[0] especially the crayfish plague: https://en.wikipedia.org/wiki/Crayfish_plague

Oh that's possible, yes. I'm not an expert and don't know if the marbled crayfish is the one on sale; I can tell the ones on sale are not the indigenous one, but not much more.

In the Netherlands the indigenous species still exists, in a single pond. Matter of time :-(

Be careful creating a market or a bounty as it creates a perverse incentive toward intentionally introducing it to news areas.

Why just asian restaurants? They're basically fresh water lobsters, you should be able to market them anywhere that serves lobster/prawn/shrimp.

A certain age cohort of Chinese people will eat anything, likely resulting from when their parents had to do just that to avoid starvation.

US-origin crayfish only look like shrimp-sized lobsters, they don't taste as good as either. They're more like if you boiled a lobster for too long and smeared it with river-bottom mud instead of butter. And at that size, the shells are a real pain.

Well, you'd do a general marketing push, but Asian markets are a fairly narrow target market, some of them specialize in spicy crayfish boils, so it seems easier since the supplier and the demand are both there and you'd get more bang for your marketing buck. But if you could pick up 150 crawfish in an hour with just your hands, think of what a lighted trap could do overnight.

I was thinking about just this solution, eating them! In Sweden crayfish is very popular and crayfish catching is a popular activity, and there are even competitions.

This species was found here in 2012, but only sporadically it seems after that, so we might not have a problem yet.

Not just Asian. Crayfish are popular in Cajun and other Southern cooking.

Sure. But I'm pretty sure that there are more Asian people than Cajun/Southern people, and if you want to create a large market, it makes sense to focus on the really big markets.

You're getting downvotes but it's a completely reasonable effort, cf blackened snakehead and lionfish.

Got a problem? Eat it! I like your style

If the article is correct that these species can go extinct easily, then it is probably a bad idea to develop it as a food source. It could lead to a situation where millions of people become dependent on it, and then it suddenly becomes unavailable.

Is "mutant" here used to invoke comic book imagery, or is there some meaning in science writing to "mutant species"?

Mutant is a scientific term taken over by comics it means something changed in the gene that made it different from others. Mutants are actually quite common in the animal kingdom but usually die out as they can rarely reproduce if they reproduce they become a seperate and unique species the difference with this crayfish is that it is reproducing on its own. We are all descendents of mutants that seperated into homospaiens.

>Mutants are actually quite common in the animal kingdom but usually die out

Naw, every person is likely to carry at least one de novo mutation in their genome. Mutations happen constantly, they're just usually unremarkable.

Hence the pondering about the meaning of "mutant species".

Yes, "mutant" and "mutation" are legitimate terms in genetics, and they apply here.

Very well written article to capture your attention on a subject that isn’t really unique

Missing from the article is that unlike most self-cloning animals (I know of no other), Marmorkrebs, has a triploid genome.

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