Limpets
| Limpets | ||||||||||||
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Pond limpet |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Acroloxidae | ||||||||||||
| Thiele , 1931 |
The pond limpets (Acroloxidae) are a family of freshwater snails belonging to the order of the pulmonate snails (Pulmonata). The German name is a bit misleading, since representatives of this family have long been able to appear not only in ponds, but also in lakes, slowly flowing waters and in cave waters. The family is counted here to the subordination of the water snail (Basommatophora).
features
The housings are cup-shaped and more or less longitudinally oval. The apex points back to the left. The animals are anatomically right-oriented, which means that they can be distinguished from the numerous other cup-shaped freshwater snails (in Europe especially Ancylus and Ferrissia species), which belong to the poppy -mouth snails and are left-oriented. On the right side, they have developed a secondary gill in the lung cavity.
Way of life
The gas exchange takes place directly from the water phase through the skin and the secondary gill into the body; the snails therefore do not have to come to the surface of the water to breathe air. Algae that grow on the substrate ( periphyton ) serve as food, as well as parts of rotting plants.
distribution and habitat
The family is common in the temperate latitudes of the northern hemisphere. The occurrence of special species in old lakes ( Lake Ohrid and especially Lake Baikal ) is striking . The snails often live in stagnant or slowly flowing waters on aquatic plants, but also on wood or stones. Only one species occurs in Central Europe; s. on this Acroloxus lacustris .
Paleontology and evolution
Due to their morphological and molecular genetic characteristics, the Acroloxidae are considered to be relatively original representatives of the Hygrophila ( water snail in the sense of the word ). Due to the small size and lack of features of the shells, the fossil location has not been clarified. Since the Middle Cretaceous ( Coniacium , about 87 million years ago) individual finds have been assigned to the family of limpets; but it is to be expected that the family is of older origin.
Systematics
The family is the only family within the superfamily Acroloxoidea and, according to the current system, comprises three genera with approx. 10 species:
- Acroloxus Beck, 1837 or 1838; about 5 kinds; four species in Europe and one species in North America
- Pseudancylastrum Lindholm, 1909; about 3 species in Lake Baikal
- Gerstfeldtiancylus Starobogatov, 1989, with approx. 2 species
Individual evidence
- ^ MJ Benton (Ed.): The Fossil Record 2. Chapman & Hall, London 1993.
- ↑ AA Shirokaya and Peter Roepstorf: Morphology of syncapsules and the duration of embryology of Baikalian endemic limpets (Gastropoda, Pulmonata, Acroloxidae). Berliner Palaeobiologische Abhandlungen, 4: 183–192, Berlin 2003 ISSN 1612-0361
literature
- Peter Glöer: The animal world of Germany. Mollusca I Freshwater gastropods of Northern and Central Europe Key to identification, way of life, distribution. 2. rework. Ed., 327 pages, ConchBooks, Hackenheim 2002 ISBN 3-925919-60-0