Much like the fast reproduction and rapid overpopulation of Tribbles in the original Star Trek television series, marbled crayfish, a species that literally clones itself, is now overtaking Europe.
A new study published in Nature Ecology & Evolution explores the remarkable evolution of the far less cuddly crayfish, Procambarus virginalis, a species that only developed 25 years ago after a single mutation in a single animal allowed the marbled crayfish to clone itself, in a process biologists call parthenogenesis. It’s a trait shared by Crustacea, but never detected in decapods like the marbled crayfish until 2003.
According to Frank Lyko, one of the authors of the study, each marbled crayfish can simultaneously produce hundreds of eggs. This — as well as the species’ ability to thrive in a wide variety of habitats — has led to an invasion of the animal across European freshwater ecosystems, expanding even to Madagascar, threatening native crayfish populations.
It began with two slough crayfish mating. One of those original slough crayfish had a unique mutation where one sex cell had two copies of each chromosome instead of the usual one. During mating, the two sex cells merged and created a female crayfish embryo with three copies of each chromosome.
This Crayfish Eve didn’t need an Adam to induce her own eggs to divide into embryos and produce all-female offspring with identical copies of all three sets of chromosomes. All the marbled crayfish Dr. Lyko’s team analyzed were virtually genetically identical.
The new daughters created by this union — as well as their daughters and their daughters’ daughters — represent an entirely new species because, though male slough crayfish would try to mate with them, no progeny would result.
Approximately 1 in 10,000 species are both all-female and parthenogenic. Asexual species have the evolutionary advantage of producing only fertile offspring, a powerful means of exploding the population in the short-term. The downside is, in the long-term, asexual species typically die out faster.
Sexual species are advantaged in the long-term because diversification of the gene pool optimizes adaptation to harmful pathogens that, if deadly to one clone, would likely be just as deadly to all its genetically identical offspring.
So, while the marbled crayfish are thriving now, they wouldn’t be the first European conquerers to enjoy a short reign.
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