River dwarf snail
| River dwarf snail | ||||||||||||
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Sadleriana fluminensis from Italy |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Sadleriana fluminensis | ||||||||||||
| ( Küster , 1853) |
The river pygmy snail ( Sadleriana fluminensis ) is a rare species of the genus of pygmy snails ( Sadleriana ) from the family of water snails (Hydrobiidae).
features
River dwarf snails are very small, the shell is approx. 3.2 mm high and 3 mm wide and almost spherical in shape. The case itself is brown. It is often covered with a green coating of algae, especially when it is found in a bright environment.
Taxonomy
The pygmy snails can only be anatomically determined with certainty on the basis of the sexual organs . Also sequencing of DNA must often be used. Older information based on empty shells can therefore be problematic, as some species are very similar to one another.
distribution
The river dwarf snail ( Sadleriana fluminensis ) occurs in northern Italy, Slovenia, Croatia and Bosnia-Herzegovina. The scattered occurrences today can be interpreted as relics of an ice age coherent distribution, when the Adriatic was partially dried out and the rivers shared lower courses.
Way of life and ecology
Dwarf snails need largely constant temperatures in their habitat. They live almost exclusively in cold streams or rivers and are so-called pointer types for pure water. Hundreds of animals per square meter can live in suitable habitats. Mostly they occur together with other snail species, e.g. in rivers around the upper Adriatic. B. Sadleriana fluminensis with Emericia patula and Theodoxus fluviatilis .
They feed on diatoms , blue algae and green algae , which they graze on the surface of stones in the water.
They are highly specialized and therefore very well adapted to the nutrient-poor habitat. Due to the low ecological amplitude , they react to changes in their habitat within a short period of time with a decreasing number of individuals or even local extinction.
It is spread by larger animals, on which snails or their eggs are transported from one body of water to the next.
Danger
Dwarf snails are endangered by water barriers and water use (especially in dry regions where excessive water use in summer causes many brooks to dry out) as well as construction work in the vicinity of the water body. Ingress of nitrogen from the air or from adjacent agricultural areas lead to eutrophication and the overgrowth of the substrate by algae or aquatic plants.
The IUCN classifies the widespread and especially in Friuli frequent sadleriana fluminensis as "not at risk" (least concern) one.
literature
- Clessin, Stephan (1887): The mollusc fauna of Austria-Hungary and Switzerland . < http://www.biodiversitylibrary.org/bibliography/60371 >
- Glöer, P. (2002): The freshwater gastropods of northern and central Europe . In F. Dahl, Die Tierwelt Deutschlands, 73rd part. ConchBooks: Hackenheim.
Web links
- Sadleriana fluminensis inthe IUCN 2012 Red List of Threatened Species . 2. Posted by: Seddon, M., Cianfanelli, S., Bodon, M., Giusti, F. & Manganelli, G., 2011. Retrieved January 5, 2016.