Photo/IllutrationA mystery crayfish that was found in Shigenobugawa river in Matsuyama (Hidekazu Fujiie)

  • Photo/Illustraion

MATSUYAMA--War must be declared on the alien mystery crayfish because it clones itself without mating and its population could explode and threaten local species of animals, an expert biologist warns.

"We need to wipe them out as soon as possible,” said Ushio Nishikawa, an associate professor of conservation biology of Kanazawa University's Institute of Nature and Environmental Technology, after the mystery crayfish was found in the Shigenobugawa river here.

The crustacean is always female and is extremely fertile because it is parthenogenetic, which means it lays eggs that do not require sperm for fertilization.

“The population of these creatures shot up in a short period of time overseas such as the African island nation Madagascar. If the species takes root in Japan, it could threaten indigenous creatures," Nishikawa said.

The mystery crayfish, called marbled crayfish or marmorkrebs overseas, was found by researchers led by Mikio Inoue, professor of stream ecology of Ehime University’s Faculty of Science.

They have been conducting environmental research at Matsubaraizumi spring, which feeds into the Shigenobugawa river, since spring 2015.

The mystery crayfish was first found in the summer of that year and another discovered in autumn 2016, according to Inoue who sent photographs of the crustaceans to Nishikawa, who identified them.

It’s uncertain where the 10-centimeter-long creature originally come from, said Nishikawa.

The mystery crayfish is sold as a pet in Japan and are available at online auction sites.

Importing the crustacean is banned under the Invasive Alien Species Law. The crayfish currently being distributed are probably descended from one that was imported before 2005 when the law came into effect, according to the Environment Ministry.

“We have not yet confirmed any cases of the mystery crayfish rooted in a particular area in Japan,” said an official of the Environment Ministry’s Office of Alien Species Management. "But if it is likely to cause damage to conventional species so early measures against it is required.”