Viviparus viviparus (Common River Snail)

Viviparus viviparus is a species of large freshwater snail with a gill and an operculum, an aquatic gastropod mollusk in the family Viviparidae, the river snails. This is a cold water species found in many European countries. Viviparus viviparus is largely confined to major, slow-moving, lowland rivers and to lakes and prefers calcareous (base-rich) waters. They are often found in deep water. They are sometimes found in dense clusters (reaching thousands of individuals) on submerged branches and on various man-made objects present under water. More rarely, they are present more scattered in bottom mud, and then are much more discreet. The snails are also found in canals, artificial ponds, the water behind dams and in reservoirs but usually not in small isolated standing waters. Viviparus viviparus requires high oxygen content.

The height of the shell is 25 – 35 mm. The width of the shell is 20 – 26 mm. Males are 2 mm smaller than females of the same age. The shell colour is dark greenish brown or greyish yellow with three reddish brown spiral bands. It is striated but not with a hammer pattern. The shell apex is blunt (more pointed in other Viviparus species). The shell has 5.5 – 6 weakly convex whorls. The last whorl is relatively large compared to that of other Viviparus species. The umbilicus is narrow. The animal can lock itself behind a round lid adorned with concentric striations (the operculum), allowing it to protect itself for several months if necessary – from dehydration. Once closed the operculum is flush with the opening of the shell. The operculum is attached to the dorsum and to the rear foot of this mollusc, the body of which is wide and T shaped and whose colour varies from spotted grey to greenish to orange. Snail’s mouth has a radula and a respiratory siphon opens on the right side of the head, feeding gills located in front of the heart. This trap also allows the snail to filter the water. There are two short tentacles; the eyes are on the external side of each tentacle.

 

 

As its latin name suggests, it is a viviparous (oviviparous) snail, a rare phenomenon among snails. The female gives birth to live young, after producing eggs that hatch internally. The naturalist Jan Swammerdam, was the first to recognize the viviparous character of this species to which he gave the name of Cochlea mirabilis and Cochlea vivipara but he seems not even have understood that there were males and females in this species (most other snails are hermaphroditic). 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. The male is distinguished by a shorter and round tipped right tentacle, which also serves as a penis during fertilization: the female is usually slightly larger than the male at the same age, and it has two identical tentacles. Sexual maturity is reached after two years, when the snail is about 2 cm long. Each female bears eggs (up to 30 and at all stages of development) with a size of 3 to 7 mm in diameter and up to the full development of the embryo. 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. After producing all its young, the female dies.

Viviparus viviparus can do a good job keeping a tank or an outdoor pond clean by eating uneaten food, dead or decaying plant matter, debris, detritus, and soft algae build-up on hard surfaces. This snail can be seen for hours on end canvasing the tank for edible matter.

Viviparus viviparus is a cold-water species. The snails should be kept at 10°C – 25°C. Recommended pH 6.0 – 7.5 with water hardness at around 8 – 20 dGH. These snails can be kept outdoors all year round without any problems. They survive under ice during winter period.

When keeping Viviparus viviparus, it’s important to test tank water regularly. Make sure Ammonia and Nitrite levels are at 0 ppm, and control Nitrate levels as well as organic matter accumulation with regular partial water changes. As with other shelled tank mates, be very careful when using medications and plant fertilizers as some of the ingredients may be harmful. Most importantly, avoid copper. Even in small amounts, copper can be fatal.

Viviparus viviparus eating a balanced diet of debris, aquarium algae, vegetables and commercial supplements will grow quickly and steadily. This is particularly true with Calcium. If Calcium levels are sufficient, a snail will grow thick, healthy, crack-free shells.

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