Inside Jordan Peele’s Incredible 2019 Horror Movie We, an army of human doppelgangers called The Tethered arises to take the place of the existing human population. It touches on some of our core fears, that we might actually be the monsters and that another version of ourselves might usurp our privileged place on Earth. It is later revealed that the Tethered are genetic clones created by the government and abandoned.
Human cloning is still beyond our reach. But nature locked the process. A number of animals, including some reptiles, birds, and sharks, clone themselves through asexual reproduction known as parthenogenesis. This elite club of clone animals has a new member.
For the past few decades, the planet has been at the mercy of a ten-legged, multi-clawed crustacean, voraciously creating a clone army bent on world domination. No, this is not an interplanetary intruder or the result of an uncontained government experiment. It’s biology gone wrong, or if you’re a marbled crayfish, biology gone horribly wrong.
Today, the freshwater marbled crayfish populates various ecosystems across Asia, Europe, and Africa, and they all trace back to a single genetically identical individual born less than three decades ago. Their precise population number is unknown, but an estimated 23,000 people live in a single small lake in Germany, which measures less than a tenth of a square kilometer, so it stands to reason that there are many. .
Their invasive nature and rapid spread over a significant portion of the planet have made them an intriguing target for scientific research. An international team of scientists performed an analysis of their genome in an effort to uncover their origin and discovered that they were stranger than we could have dreamed. Their findings were published in the journal Evolution of nature ecology.
The marbled crayfish genome is 3.5 million base pairs long – that’s more than the human genome – made up of about 21,000 genes of 92 chromosomes. What is unusual is that instead of the expected two copies of their chromosomes, marbled crayfish have three. Their genetic makeup is similar to that of the close relative slough crayfish, which has led scientists to conclude that the first marbled crayfish arose from an unusual chance of breeding when two slough crayfish mated.
Additionally, it seems that Slough’s parents come from different parts of the world, making it unlikely that they met in the wild. Instead, it is thought that they could have been dropped into the same aquarium and encountered in captivity where they would later give birth to their unusual offspring.
That could have been the end of the story, but this new genetic aberration had to somehow escape the reservoir – or one of its own cloned offspring did – and s made his way into nature. Clonal species are often thought to be more at risk because they lack the genetic diversity that accompanies sexual reproduction, but that hasn’t been a challenge for the marbled crayfish, at least until now.
Despite its unusual origin and asexual reproduction strategy, it has managed to establish itself all over the world. Although it has not yet appeared in the wild of the United States, some regions are taking preventative measures, designating them as prohibited, even in the aquarium trade where they have become popular.
It is a valid strategy. Once they’ve found their way into an ecosystem, there’s probably no stopping them. A single individual can lay 700 eggs, all copies of itself, and it can survive drought conditions by burrowing into the ground and migrating over land. All the while they outnumber and reduce the number of endemic species.
Let’s just hope the marbled crayfish never sets its sights on humanity. If they do, we may never be able to stop them.