Sounds like the start of science fiction film, or even our April Fool’s blog about treating a Tribble, but this crawfish is really a mutant, it’s really a clone, and its population has really leaked into the wild where it is growing at an exponential rate.
According to the New York Times, a genetic variant on a North American crawfish is believed to have naturally mutated in a household aquarium in Germany. Once mutated, this 6-inch long arthropod was able to reproduce without a mate, producing hundreds of eggs at a time, all of them fertile, and all of them capable of growing into an exact genetic copy of their mother.
Escapes into Local Waters
The original owner of the mutant, overburdened by so many young crawfish, is believed to have given them away to other aquarium enthusiasts. Soon the species ended up in fish tanks in other parts of Germany, in pet stores, and in a few cases, because they were reproducing so quickly, in local waterways where they were dumped because of their explosive growth.
All Off-Spring Are Female and All Can Reproduce Asexually
Because the creatures are clones, all offspring are female, but this doesn’t stop the species from reproducing. Because all the females share the mutation of their mother, they are all able to reproduce asexually without a male. It’s like a race of Amazon women, except crawfish, where males are unnecessary for the continuation of the species.
Asexual Reproduction: Not As Uncommon As You Think
Asexual reproduction is not unheard of. Of the six kingdoms of life, all have at least one species that primarily reproduces asexually and many species that are capable of both sexual and asexual reproduction, but this form of reproduction has its drawbacks. Organisms that reproduce asexually are exact genetic copies of their parent, leaving the organisms, and indeed the entire species, susceptible to the same pathogens. A single ‘bug’ or environmental sensitivity can wipe out the entire species since there is no genetic diversity to impart some protection to portions of the population.
In sexually reproducing organisms, like dogs, cats, and people, sex cells undergo a process called meiosis where pairs of chromosomes separate and form haploid cells or cells that contain only one copy of each of the organism’s chromosomes. When creatures mate, their respective sex cells fuse, the cell’s chromosome numbers are returned to their normal diploid number, and the cell is capable of growing into a new adult.
In asexual reproduction, the sex cells go through meiosis, but then recombine to form a diploid cell without the introduction of chromosomes from another creature.
Asexual reproduction is common in the plant world. Indeed, if you have ever planted potatoes, you’ve tinkered in a form of asexual replication known a vegetative propagation. Potatoes can be grown by cutting them into small pieces and burying them in soil. Each piece will grow into an exact genetic copy of the plant that will produce a genetically exact form of the original potato. The apples that you buy in the store are all reproduced asexually. Apple varieties like Macintosh, Gala, Honeycrisp and Delicious cannot be grown from their respective parent’s seeds since the seeds were injected with different genetic material when the apple blossoms were pollinated (ironically by another asexually reproduced organism, the female honeybee). To get around this, orchard growers graft pieces of the original parent plant onto new apple stock and regrow branches of the original fruit variety. There are some apple varieties that have been propagated this way for centuries. And here’s one last curious example. For reasons not completely known, some turkeys have the ability to reproduce asexually in a process called parthenogenesis where the genetic material of the hen’s egg cells undergoes meiosis, but recombines to form diploid ova capable of growing into adult birds.
No one knows how the story of this mutated crawfish will end, but we should worry less about its ability to reproduce asexually and more about its invasiveness and adapatabilty to environs different from those in which it was first born. Invasive species have been known to utterly destroy native inhabitants. The Lionfish another aquarium favorite and native to the Indo-Pacific sea, has invaded Atlantic waters and is causing a great deal of upset to the environment. Here in the Northeast for example, large swaths of Ash trees have been killed by the invasive ash tree borer, a beetle that arrived in a shipping vessel in Michigan in 2002.
To guard against invasive species, never release turtles, waterfowl, snakes or aquarium fish into the environment. Beyond the fringes of their native habitat, these creatures are free of the natural predators that would normally keep them in check. They compete with native species for food, shelter, and nesting grounds. While you believe that all creatures deserve the right to be free, that freedom can come at a catastrophic cost.