Article: The rich genetic detail gave the scientists a much clearer look at the freakish origins of the marbled crayfish.
It apparently evolved from a species known as the slough crayfish, Procambarus fallax, which lives only in the tributaries of the Satilla River in Florida and Georgia.
The scientists concluded that the new species got its start when two slough crayfish mated. One of them had a mutation in a sex cell — whether it was an egg or sperm, the scientists can't tell.
Normal sex cells contain a single copy of each chromosome. But the mutant crayfish sex cell had two.
Somehow the two sex cells fused and produced a female crayfish embryo with three copies of each chromosome instead of the normal two. Somehow, too, the new crayfish didn't suffer any deformities as a result of all that extra DNA.
It grew and thrived. But instead of reproducing sexually, the first marbled crayfish was able to induce her own eggs to start dividing into embryos. The offspring, all females, inherited identical copies of her three sets of chromosomes. They were clones.
(The full research paper can be found here, but it's less quotable and pretty dense)
Fascinating reading, especially if you can make your way through the full research paper. Somehow - probably in a German aquarium - a single crayfish hatched which lays all its eggs fertilised with clones of itself, and which is infertile with males of its parents species. And it just reproduces endlessly, each egg hatching into a self-clone. The paper makes a note of how it's really amazing to have caught a clonal species so young, because it doesn't have most of the normal things we see in clone species DNA of built up duplications and replicated chromosomes - it's basically "pure" with the initial mutation because we're so close to the species origin.
Oh, and of course, that makes it an invasive alien clone since it just keeps on reproducing as long as it has food.
