Florida Mutant Crustacean Takes Over the World With Army of Clones

[Vinyadan]

Twenty-five years ago, something unusual happened while a couple of slough crayfish was mating. The sex cell of one of the two had undergone mutation: it contained two copies of each chromosome, instead of the normal one. This lucky cell fecundated (or was fecundated), which resulted into an egg and an embryo. This probably happened in a German aquarium.
This embryo grew into a healthy female crayfish, whose cells contained three copies of its chromosomes, instead of the normal two. This is probably why it could reproduce asexually. Since all new crayfish born this way was genetically identical to the mother (perfect clones), it also inherited asexual reproduction.

As a result, the numbers sky-rocketed. There now are millions of these animals. All of their eggs (hundreds a batch) have the potential for development into adulthood. Marble crayfish (the clones) can mate with male slough crayfish (the vanilla version), but will not be fecundated by them. They will only generate more clones.

Their diffusion was probably man-dependent at first: people with water tanks found themselves with lots of crayfish, which they gave to friends, who would later throw excess specimen into ponds and lake, where the crayfish would thrive and multiply, and even migrate on land in search for new waterways. Right now, they are found mainly in European waters, but also in Madagascar and Japan. While slough crayfish only lives in river estuaries in Florida and Georgia, there is no known marble crayfish living in the wild in North America.

They probably are the species that was identified at the earliest after its birth.

https://www.nytimes.com/2018/02/05/science/mutant-crayfish-clones-europe.html

[anjxed]

I have just one question. Is it tasty? If it is. Market it in China, problem solved

[ufo]

I have just one question. Is it tasty? If it is. Market it in China, problem solved

Why China? Northern European coastal communities have a pretty strong inclination towards eating crayfish, for obvious reasons. I remember when this species started showing up, the fishers where I'm from were preeetty excited.

[halfeye]

Our native freshwater crayfish are being overrun by American ones already.

These marble crayfish will overextend themselves very soon. Otters and mink will like them, if nothing else does.

[AMX]

Our native freshwater crayfish are being overrun by American ones already.

These marble crayfish will overextend themselves very soon. Otters and mink will like them, if nothing else does.

I'm thinking bacteria, or maybe fungi - it's only a matter of time until some pathogen adapts to the marbled crayfish, and because they're all clones it'll burn through the entire population like nobody's business.

IMO, the only question is whether any other crayfish will be left at that point.

[Yora]

Somehow some exclusively parthenogenetically reproducing animals have managed to stick around for a very long time. It's not that uncommon for arthropods. It's a genetic dead end, but the ultimate end for this lineage could be quite long off indeed.

[hamishspence]

Somehow some exclusively parthenogenetically reproducing animals have managed to stick around for a very long time.

The ones that usually spring to mind are "greenfly" aphids. The perfect real-life example of McCoy's statement about tribbles:

"Nearest I can figure is that they're born pregnant - which would be quite a timesaver".

https://en.wikipedia.org/wiki/Aphid

[anjxed]

Why China? Northern European coastal communities have a pretty strong inclination towards eating crayfish, for obvious reasons. I remember when this species started showing up, the fishers where I'm from were preeetty excited.

Because there are a billion people in China. The middle class is basically 300 million people it would need a lot of crayfish fast.

[Murk]

Somehow some exclusively parthenogenetically reproducing animals have managed to stick around for a very long time. It's not that uncommon for arthropods. It's a genetic dead end, but the ultimate end for this lineage could be quite long off indeed.

It's not necessarily a genetic dead end. It's very possible to mutate, develop and evolve without sexual reproduction. Lots of creatures do it. Sex is way overrated.

[Anonymouswizard]

It's not necessarily a genetic dead end. It's very possible to mutate, develop and evolve without sexual reproduction. Lots of creatures do it. Sex is way overrated.

Yeah, sex is an advantage in spreading traits faster, kind of, but it's nowhere near required for evolution. Unless I'm completely forgetting my limited knowledge of the subject.

[Lvl 2 Expert]

Yeah, sex is an advantage in spreading traits faster, kind of, but it's nowhere near required for evolution. Unless I'm completely forgetting my limited knowledge of the subject.

It is rather limiting in species with a sort of long generation time and a lack of horizontal gene transfer though.

For the first part of that sentence, let's say you have a bacterial colony, sitting inside the E. coli long term evolution experiment (https://en.wikipedia.org/wiki/E._coli_long-term_evolution_experiment). This is a thing, they're bottles of medium the bacteria can barely survive on unless they learn how to break down a nutrient they can't currently digest which in this medium is plentiful. As soon as a single bacterium develops the right mutation it starts multiplying rapidly, because lots of free food and no competition. Within a day the medium is overgrown with the new mutant strain. It might take a few weeks for the last originals to die out, but after that first day the colony has essentially fully adapted to the circumstances, because almost all bacteria there are the new mutants now. For asexually reproducing elephants this trick would be a lot harder. A single elephant with a mutation that makes it not grow tusks will be successful due to not being poached, but it can produce maybe a dozen or so now elephants in its lifetime, after a hundred years there will still be plenty of tusked animals (or rather: there will still be a small number of mutants, and if the rest of the population has been shot by then the species has a good chance to disappear altogether, or will at least need centuries to get back up to halfway decent numbers). These crabby lobsters are somewhere in between a bacterium and an elephant. Most creatures with roughly their speed of reproduction produce sexually.

Horizontal gene transfer is another trick bacteria use. Let's say there is a new strain of bacteria. It's resistant to common antibiotics, so it's having a good time hanging out in hospitals. It's kind of noticeable and deadly though, so patients tend to get hospitalized or even isolated, and the mutation never really spreads. Another strain or even a different species of bacteria meanwhile has adapted to not be too dangerous. It causes mild flu-like symptoms and many people just tough it out rather than seeing a doctor. But this bacteria is not antibiotics resistant, so if it shows up in some of the best populations for diseases to thrive, like nursing homes or kindergartens, the sick people get treated and the outbreak is contained. Bacteria have ways to get either the resistant genes into the less lethal species or the other way around, recombining their DNA into the perfect spreadable disease that will have lots of offspring across the world. Some species semi-regularly just incorporate random DNA from dead bacteria they come across, for instance. This gene transfer essentially does the same job sexual reproduction does: it can make traits developed by non-related individuals come together in a single individual. Larger animals have limited access to this sort of thing, for instance viruses can carry small bits of DNA from one person or species to the next, but it doesn't reach anywhere near the same scale.

So no, it's not required, but the fact that most of the larger animals around us use sexual reproduction does say something about its usefulness. The ability to evolve is itself a thing evolution can select for. If your species has a hard time adapting, chances of it disappearing when circumstances change (say, with the rise of a new subspecies of heron specialized in eating these crustaceans) go up. And an asexual species (it's not even facultative like how a potato plant can spawn sexual and asexual offspring or how C. elegans can essentially mate with itself, all newborns are clones) with a relatively long generation time and limited horizontal gene transfer tend to have a harder time adapting.



Also, every time I see this topic title the TMNT (80's/90's series) song starts playing in my head.

[Shackled Slayer]

Lucky thing about it though is that this is occuring in crayfish, which are themselves wide spread enough that any environment they move into will likely have predators of the species to keep them in check. The dangerous bit is if they move into an uncontested environment, breed unchecked and from their radiate out in mass numbers causing sudden famines of the lower food chain base foods that form the root of the ecosystem their in, but again, such predator free environments are rare.