Acroloxidae

Teichnapfschnecke

The Teichnapfschnecken ( Acroloxidae ) are a family living in freshwater snails from the order of snails ( Pulmonata ). The German name is somewhat misleading, as representatives of this family long ago may occur not only in ponds, but also in lakes, slow-moving waters and in cave waters. The family is expected here to the subordination of water snails ( Basommatophora ).

Features

The housing is cup-shaped and more or less along oval. The apex points to the rear left. The animals are anatomically quite oriented, so they can be distinguished from the many other cup-shaped freshwater snails ( Ancylus especially in Europe and Ferrissia species) belonging to the plate and screws are left-wing, distinguished. On the right side they have developed a secondary gill in the lung cavity.

Way of life

Gas exchange takes place directly from the water phase through the skin and the secondary gill in the body; the snails do not come to the surface for the purpose of air breathing therefore. As a food serve algae that grow on the substrate ( periphyton ), partly probably rotting plant parts.

Distribution and habitat

The family is distributed in the temperate latitudes of the northern hemisphere. What is striking is the occurrence of specific species in ancient lakes ( Lake Ohrid and Lake Baikal specifically ). The snails live in stagnant or slow-flowing waters often to water plants, but also on wood or stones. In Central Europe, only one species is found; see this Acroloxus lacustris.

Paleontology and Evolution

The Acroloxidae are based on morphological and molecular genetic traits as original representatives of Hygrophila (water snails in the narrow sense ). Due to the smallness and poverty characteristic of the fossil shells situation is not clear. Since the mid-Cretaceous ( Coniacian, about 87 million years ago ) individual finds the family of Teichnapfschnecken be assigned; It is to be expected that the family senior origin.

System

The family is the only family in the superfamily Acroloxoidea and comprises according to current system three genera with about 10 species:

• Acroloxus Beck, 1837 or 1838; about 5 species; including four species in Europe and a kind in North America
• Pseudancylastrum Lindholm, 1909; about 3 species in Lake Baikal
• Gerstfeldtiancylus Starobogatov, 1989, with about two types