No, but that's nothing to be afraid of, even for bathers!
Small, transparent freshwater jellyfish have been seen in some Swiss lakes since the 1960s. In 2003, there was a major proliferation of these animals in Lake Geneva.
But why do they only appear in certain years?
When the water reaches 25 degrees for a long period, as it did during the 2003 heatwave, the polyps living at the bottom of the lake transform into jellyfish and then rise to the surface to feed on microplankton. Polyps are a fixed form of cnidarians (aquatic animals that include corals, anemones and the freshwater hydra). The second form of cnidarians is the swimming form known as a jellyfish.
These jellyfish can reach the size of a 2.- coin! Even if they are like their ocean counterparts: made up of stinging cells, they won't bother bathers.
When you put a jellyfish on a makeshift boat and it drifts with the winds in stormy seas, it's called a "jellyfish raft" ....
But that's another story!
For further information:
RTS
Lémantines.ch
