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. Most crayfish—and most other animals—have two sets, one inherited from the mother and the other from the father. It’s unclear, however, whether these three sets of chromosomes are the cause or consequence of its self-cloning ability. Despite having the DNA sequence in hand, “the reason and origin of parthenogenesis is still somewhat mysterious,” says Gerhard Scholtz, a zoologist at the Humboldt University of Berlin who first described the marbled crayfish in 2003.

Lyko is interested in the marbled crayfish because he studies epigenetics—or how genes are turned on and off without changing the underlying genetic code. Normally, he studies this in cancer cells, as he works at the German Cancer Research Center. But the marbled crayfish are an intriguing model system for epigenetics. They are virtually identical genetically, yet they differ in size and pattern. These changes may be epigenetic in nature.

Ranja Andriantsoa / Deutsches Krebsforschungszentrum

Lyko also collaborated with scientists in Madagascar, where the marbled crayfish is displacing the native crayfish species. Their interest is more ecological. In the past 10 years, they estimate, the marbled crayfish population has expanded its area in Madagascar 100-fold—despite, or perhaps because of, a local appetite for them. Marbled crayfish evolved from a species native to Florida, so they are used to a warm and humid climate. “You’ll find that in Madagascar. Not so much in Germany,” says Lyko.

Yet marbled crayfish are in German lakes, too. Lyko says that a graduate student at his institute had found marbled crayfish in one near her family’s house. They threw some of the crayfish on the grill. Lyko himself is less keen on eating the clone invaders. “I tried other crayfish once,” he says. “I didn’t like them so much to be frank, so I’m not in a rush to eat marbled crayfish.”