No one knows exactly when the clones first appeared, but humans only became aware of them in the early 2000s.
It was a German aquarium owner who first brought it to scientists’ attention. In 1995, he had acquired a bag of “Texas crayfish” from an American pet trader, only to find his tank inexplicably filling up with the creatures. They were all, it turns out, clones. Sometime, somewhere, the biological rule that making baby crayfish required a mama crayfish and papa crayfish was no longer inviolate. The eggs of the hobbyist’s all-female crayfish did not need to be fertilized. They simply grew into copies of their “mother”—in a process known as parthenogenesis.
Crayfish specialists were astonished. No one had seen anything like it. But the proof was before their eyes and in 2003, scientists dubbed the creatures marbled crayfish, or Marmorkreb in German.
Scientists quickly realized the marbled crayfish were not just in German aquariums. The self-replicating creatures were out in the wild, and they were aggressive invaders. “Every single one has the ability to reproduce. Every single one could start a new population,” says Zen Faulkes, a crustacean researcher at the University of Texas at Rio Grande Valley who keeps a map of marbled crayfish invasions...
...For the first time, scientists have now fully sequenced the DNA of the marbled crayfish. In fact, they sequenced not one but 11 crayfish—including those originating from German pet shops as well as wild ones caught in Madagascar. The creatures are indeed clones of each other, all descended from a single crayfish that somehow gained the ability to reproduce on its own. They had remarkably little genetic diversity. At most four letters in their entire DNA sequence differed in a meaningful way
Another intriguing fact, says Frank Lyko, who led the study, is that marbled crayfish are triploid, meaning they have three sets of chromosomes...
Read it all here: https://www.theatlantic.com/science/arc ... es/552236/
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