Pond limpet
| Pond limpet | ||||||||||||
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Pond limpet ( Acroloxus lacustris ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Acroloxus lacustris | ||||||||||||
| ( Linnaeus , 1758) |
The pond limpet ( Acroloxus lacustris ) is the best known and in Central Europe the only representative of the genus Acroloxus . It lives in fresh water and is neither related to the marine limpets , nor to the cap snails (genera Ancylus , Ferrissia , etc.) that are found in freshwater around the world , which are counted among the pinnacle snails .
features
The shell of the pond limpet is thin-walled, elongated, cap-shaped, without turns and from yellowish-gray to brown in color. It becomes about 7 mm long, 3 mm wide and 2 mm high. However, these dimensions can vary depending on the substrate. The apex of the housing points to the left rear. On thin plant stems there are specimens with narrow, parallel-sided housings, on leaves and stones rather broad oval ones. The much smaller soft body is covered like a roof by the flat housing. The other characteristics are the same as for the entire genus (lung cavity regressed; secondary gill and genitals are on the right side).
Similar species
Confusion with one of the other four species of the genus Acroloxus is practically impossible due to the apparently non-overlapping distribution areas in nature. At first glance, however, the species can be confused with the river cap snail , which, however, is anatomically oriented to the left and belongs to the family of pancake snails (Planorbidae). It is even easier to confuse it with the species Ferrissia wautieri and / or Ferrissia clessiana , which may have been introduced from North America (the exact classification and naming of this form, which has only been known in Central Europe since 1960, is currently controversial), which, however, is also anatomically left-oriented.
Occurrence
Acroloxus lacustris is adaptable and is found in fresh water with pH levels between 6 and 8.9. This snail prefers to live in the reed zone of stagnant or slowly flowing water with abundant vegetation. There it sits on the stalks of plants or on the underside of floating leaves and grazes on the cover of diatoms and cyanobacteria (blue-green algae). The saprobic index for this species is 2.2.
Way of life
The gas exchange takes place directly from the water phase through the skin and the auxiliary gills into the body. The snail does not take in atmospheric air on the water surface.
The pond limpet is a hermaphrodite and can fertilize itself, but it can also be fertilized. The hatching from the clutches , which consist of flat, water-clear, round, 2–4 mm large capsules and contain only a few (maximum 10) eggs, can take up to 10 days, depending on the water temperature.
literature
- Wolfgang Engelhardt: What lives in pools, brooks and ponds? , Kosmos-Franckh, Stuttgart, 12th edition. 1986. ISBN 3-440-05444-6 .
- Rosina Fechter, Gerhard Falkner: Mollusks - Steinbach's Nature Guide , Mosaik-Verlag, Munich 1990. ISBN 3-570-03414-3 .
- Peter Glöer: The animal world of Germany. Mollusca I Freshwater gastropods of Northern and Central Europe, identification key, way of life, distribution. 2. rework. Ed., 327 pages, ConchBooks, Hackenheim 2002. ISBN 3-925919-60-0 .
Individual evidence
- ↑ Meyer, Detlef .: Macroscopic biological field methods for assessing the water quality of rivers: with lists of species for beginning and experienced investigators and detailed descriptions and images of the indicator organisms . 4th, unchanged. BUND, Hannover 1990, ISBN 3-9800871-4-X .