Mutant all-female crayfish prompt invasive species fears | News | DW | 12.02.2018


Mutant all-female crayfish prompt invasive species fears

The self-cloning crustaceans exploded amongst Germany's aquarium hobbyists in the 1990s. Now it has become an invasive species in countries as far away as Japan and Madagascar.

Marbled crayfish (picture-alliance/dpa/R.Andrian)

The government of Canada warned the public on Sunday not to keep marbled crayfish as pets amidst a growing controversy over the self-cloning species that does not need males to survive.

Marbled crayfish, a freshwater crustacean, arrived on the scene between 25 and 30 years ago as mutated descendants of the slough crayfish, but with three sets of each chromosome instead of two – making them all female and able to reproduce without mating. They came to widespread attention when they became extremely popular on the pet market in Germany in the 1990s.

According to a new study published in Nature, Ecology and Evolution, a problem soon emerged: marbled crayfish, also known by their German name Marmorkrebs, are born ready to reproduce, and multiply so quickly that populations can easily get out of hand.

"If you have one animal, essentially, three months later, you will have 200 or 300," neurophysiologist Wolfgang Stein told Canadian public broadcaster CBC.

Crayfish inherit the earth

Desperate pet owners dumped the extra crayfish in nearby lakes, becoming an invasive species in countries as far-flung as Madagascar, Japan, and across Europe. This prompted the European Union to issue "a total ban on the possession, trade, transport, production and release of these species in the wild" in 2014.

The report in Nature, Ecology and Evolution said that the species now occupies a space the size of the US state of Indiana in Madagascar.

Although there have been no reports of marbled crayfish in the wild in North America, the US states of Missouri and Tennessee haved issue preemptive bans on the trade of the crustacean.

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