The crustacean, which is also called a "killer shrimp", can only grow up to two centimeters but cause great harm. It was discovered in connection with the municipality's annual water samples.

The bead crayfish is aggressive and risks crowding out both the bottom fauna and other small animals. The species is related to the larger predatory pearl in Lake Vättern, which received a lot of attention earlier this year.

"We are now following developments, but it is worrying of course," says Jennie Barthel Svedén, environmental officer at the County Administrative Board of Stockholm.

How the marrow crayfish ended up in Tullingesjön is not known, but now Botkyrka municipality will try to ensure that the animal does not spread.

Start the video to see municipal biologist Britta Ahlgren and the "killer shrimp" in the analysis lab in Gothenburg.