An aquarium accident may have given this crayfish the DNA to take over the world
http://www.sciencemag.org/news/2018/02/aquarium-accident-may-have-given-crayfish-dna-take-over-world

It sounds like a bad monster movie plot: A 10-legged mutant creature that reproduces asexually, escapes from confinement in Germany, and quietly begins a global invasion. Within 2 decades, clones of the voracious animal spread through Europe and Africa, bringing devastation to ecosystems and threatening native species.

That appears to be the strange-but-true story of the marbled crayfish, an invasive freshwater species suspected to have been created through a reproductive accident in an aquarium around 1995. A new analysis of the crustacean’s genome supports this unlikely origin and may help explain how the animal has subsequently spread and adapted to so many new environments.

The crayfish’s unusual evolution could also suggest a strategy to tackle a more infamous clonal monster: cancer. “In many ways, the invasive expansion of is analogous to a cancerous lineage spreading asexually at the expense of its host,” says Jean-François Flot, an evolutionary genomicist at the Free University of Brussels who was not involved with the work.

The marbled crayfish is the only crustacean that reproduces asexually, with the all-female species making clones of itself from eggs unfertilized by sperm. It has been thought to have arisen when two slough crayfish, imported from Florida for the aquarium trade in Germany, mated.

Since its discovery in 1995 in Germany, the marbled crayfish has spread across Europe and into Africa in huge numbers. “They eat anything—rotten leaves, snails or fish broods, small fish, small insects,” says Frank Lyko, a molecular geneticist at the German Cancer Research Center in Heidelberg. “This crayfish is a serious pest,” adds Gerhard Scholtz, an evolutionary biologist at Humboldt University in Berlin, who has tracked its rapid spread across the globe, including Madagascar, where its success threatens the existence of the seven crayfish native to that island country. The European Union banned the species: It must not be sold, kept, distributed, or released to the wild.

(more in link)

The story is worth reading in its entirety.

>Work in other organisms shows that having an extra set of chromosomes can boost the number of young and may help the clones adjust to new environments. “Greater adaptability is expected to enhance invasion success,” she says.<

It’s a wonder it hasn’t happened more often in evolutionary history.

OK, I can comment on this.

This sort of chromosome duplication is not unknown in humans – but the children always have major deformities and die very young.

One correction. The article says: “The marbled crayfish is the only crustacean that reproduces asexually”

It’s the only decapod crustacean that does so.

Daphnia pulex (common water flea) alternates between sexual and asexual reproduction.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2245944/

So we could probably say that the marbled crayfish is the only crustacean that reproduces exclusively asexually.

There’s a plant in Tasmania with three sets of chromosomes that can only reproduce itself by cloning, not sexually any more.