Thick-shelled River Mussel
The Thick-shelled River Mussel, (Unio crassus), is a mussel of the family Unionidae. The Thick-shelled River Mussel declined in the beginning of the 20th century everywhere in Europe due to deteriorating water quality.
As part of newly discovered reproductive behavior, this mollusc crawls up to the edge of the water, exposing its excurrent aperture, and then lets loose a stream of water. The fountain of water often contains glochidia, and it is suggested that this spurting behavior may facilitate dispersal of mussel larvae.