Viviparus viviparus

The operculum is attached to the dorsal surface of the rear of the foot of this gastropod, the body of which is wide and T-shaped, and the colour of which varies from spotted grey to greenish to orange.

The mouth has a radula, and a respiratory siphon opens on the right side of the head, feeding gills which are located in front of the heart.

This is a European species, which is found in Romania, Slovenia, Croatia, Czech Republic (in Bohemia only),[5] Germany, Netherlands, Poland, Great Britain, Ireland and other countries.

They are sometimes found in dense clusters (reaching thousands of individuals) on submerged branches and on various man-made objects present under water.

This filter-feeding habit makes this snail popular with owners of ponds or aquariums where they are known to consume filamentous algae, some microalgae, cyanophytes and waste solids, and thus help to purify and clarify the water.

Then in 1863 Émile Baudelot clearly states that among the paludines (river snails) there are two distinct sexes "The male system extends from the anterior end of the right tentacle to the top of the spire.

We may consider it four distinct portions, which are going from top to bottom, the testis, vas deferens, seminal reservoir and the penis.

At the time of their expulsion, the young are about 7 mm and their shell is already marked with the characteristic stripes of the river snails.

Drawing of the animal and shell of Viviparus viviparus ; a) head b) tentacles c) eyes d) foot e) operculum