Self-replicating crayfish threaten the ecosystem of a historic Austro-Hungarian lake

Lake Fertő has long struggled with invasive species, but the arrival of the marbled crayfish takes the problem to a new level. This crustacean reproduces without males, meaning a single individual can give rise to an entire colony.

Experts fear the lake’s fragile ecosystem will not be able to cope with such an intruder – especially as the species can also spread a deadly disease.

From German aquariums to open waters

The marbled crayfish first appeared in the 1990s among German aquarists. It originated from the American crayfish, one of whose lineages suddenly developed a new mode of reproduction. This is what makes the animal particularly dangerous.

The marbled crayfish reproduces through parthenogenesis: every individual is female and capable of producing offspring on its own. In practice, this means that even a single specimen is enough to establish a population within a short time.

Initially, the species was kept in aquariums, but because of its rapid reproduction many owners released them into nearby waters. From there, the crayfish spread across Europe and has since been recorded on other continents, with known populations in Africa and Asia as well.

In Hungary, it was first detected in artificial habitats such as thermal lakes and urban canals. Researchers now warn, however, that the real danger has only just begun.

Crayfish plague can wipe out entire populations

The animal itself is already a serious problem, but the greatest threat comes from a disease it carries: crayfish plague. This fungal pathogen is almost always fatal for Europe’s native crayfish species, which lack any natural resistance. Once it appears, it can destroy entire populations within weeks – and there is virtually no way to stop it.