Large periwinkle
| Large periwinkle | ||||||||||||
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Great periwinkle ( Littorina littorea ) |
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| Scientific name | ||||||||||||
| Littorina littorea | ||||||||||||
| ( Linnaeus , 1758) |
The large or common periwinkle ( Littorina littorea ) is a common marine snail of the coastal zones with a conical shell and a lid anchored to its base. It is also known as the edible periwinkle because it has served as food in coastal countries since ancient times. Its distribution area is the entire North Atlantic from the 43rd parallel to the North and Baltic Seas . The common periwinkle belongs to the family Littorinidae , which belongs to the middle snails (Mesogastropoda) of the front gills (Prosobranchia) within the classical system . In the phylogenetic system used here, the Littorinidae are listed in the order Sorbeoconcha .
features
The periwinkle has a 1 to 2 cm large, strong and conical shell, the color of which is variable. Based on the fine incremental and spiral stripes on the surface of the case, up to seven whorls can be recognized, with the last large turn forming the largest part. In contrast to the related species Littorea saxatilis ( small periwinkle ), the periwinkle has a pointed apex and its outer mouth lip leads at a flat angle to the edge of the housing.
Occurrence
The habitat of the periwinkle includes soft and hard soils on the wide tidal flats of the intertidal zone of protected coastal areas. However, they are particularly common in the immediate vicinity of mussel beds , groynes and piers . There is a population density of up to several hundred individuals per m². With their rasping tongue ( radula ) these graze the algae and animals that have settled there. Since it cleans the shells of sessile clams, it is often of great importance for the survival of these populations.
The hard floor is the preferred habitat of the periwinkle. The animals also crawl up on stones or stakes near the high water line. Only a few animals can be found in the silt and mixed mudflats or in the seagrass meadows : the risk of drifting through currents and surf is too high here due to the lack of or only inadequate opportunities to hold on to hold.
Adaptation to the habitat
During the periodic drying out of their habitat in the rhythm of the tides , the periwinkle collects in damp and sun-protected places when the water runs off and pulls the housing close to the ground. The periwinkle is well adapted to longer dry periods by closing the housing. If the dryness persists, she can close her housing with a horny lid, the operculum , which she wears on the back of her foot. In this state, it can survive three to four weeks without water cover. The snail can take in oxygen from the air through a tiny gap in the mouth. The absorption of air oxygen can take place due to a special adaptation of the respiratory organs. The gills of the periwinkle are reduced in favor of the wall of the gill cavities, which are heavily permeated with blood vessels. This adaptation not only enables resistance to inconsistent weather conditions, but is also able to colonize an unrivaled habitat between land and sea. In the habitat above the middle flood line, where only waves and splashes provide moisture, other marine snails and land snails cannot yet survive. In this zone only barnacles that settle on their shells can be dangerous. A thick shell of barnacles can restrict the freedom of movement of the snails and die off.
Locomotion
The periwinkle excretes a 0.5–1 cm wide band of mucus on its front body through numerous glands, on which it creeps. Together with the body impression, these bands can be seen as creeping tracks in the soft sediment of the tidal flats.
Diet and predators
The periwinkle is an unselective pasture. With the radula, diatoms and organic particles are grazed on hard and soft soils. Even young seedlings of algae and the nauplii of barnacles are eaten by the beach screw.
The sea crab is one of the predators . This emits chemical signals which the periwinkle uses as a warning signal (chemical sensors ). However, if there is microplastic in the area, the periwinkle's escape reaction is reduced or does not occur at all.
Reproduction
In its reproduction, the periwinkle is still strongly tied to the sea. The eggs are released into the sea at spring tide . The larvae go through all stages of development in the water before going on land. Other Littorina species hatch directly from the egg or are even viviparous like the small periwinkle ( Littorina saxatilis ).
use
In France and parts of the British Isles , periwinkles are eaten as "seafood", see snail (food) .
paleontology
As a key fossil in the area of today's Baltic Sea , it led to the naming of the Littorina Sea .
literature
- Bernhard Grzimek (ed.): Grzimeks animal life. Encyclopedia of the Animal Kingdom in 13 volumes. Volume 3: molluscs and echinoderms. Unchanged reprint of the dtv edition from 1979/80. Bechtermünz-Weltbildverlag, Augsburg, 2000 ISBN 3-8289-1603-1
- S. Peter Dance: Mussels and Snails . Dorling Kindersley, London, New York, Melbourne, Munchem and Delhi, 2000 ISBN 3-8310-0789-6
Web links
Individual evidence
- ↑ Laurent Seuront: Microplastic leachates impair behavioral vigilance and predator avoidance in a temperate intertidal gastropod. In: Biology Letters. 14, 2018, p. 20180453, doi : 10.1098 / rsbl.2018.0453 .