Common periwinkle

Great beach snail ( Littorina littorea )

The Great or Common beach snail ( Littorina littorea ) is a common sea snail of coastal zones with a cone- shaped housing and an anchored at its base cover. It is also known as edible snail beach, as they served in the coastal countries as food since ancient times. Its distribution area is the entire North Atlantic from the 43rd degree of latitude to the North and Baltic Seas. The common snail beach belongs to the family Littorinidae that within the classical system to the central screw ( Mesogastropoda ) is made of prosobranch ( Prosobranchia ). In the phylogenetic systematics used here, the Littorinidae be performed in the order Sorbeoconcha.

Features

The beach worm has a 1 to 2 cm strong and conical housing whose coloration is variable. Based on the fine incremental and spiral stripes on the body surface, up to seven whorls indicate the last big turn forms the largest part. In contrast to the their related species littorea saxatilis ( Small beach worm) shows the beach worm an acute housing summit and its outer mouth lip into a shallow angle to the edge of the case.

Occurrence

The habitat of the snail beach includes soft and hard floors on the vast mudflats of the intertidal zone of protected coastal areas. However, particularly often they are found in the immediate vicinity of shellfish beds, groynes and jetties. Here you will find a population density of up to several hundred individuals per square meter. This graze with their rasping tongue ( radula ) from the algae and animals that have settled there. As she cleans the dishes sessile mussels, it is for the survival of these populations often of great importance.

The hard floor is the preferred habitat of the snail beach dar. Also on stones or piles near the high water line, the animals creep up. The silt and mixing watts or in seagrass beds can find a few animals: the Verdriftungsgefahr by currents and waves is here due to missing or only defective hard Liability possibilities too high.

Adaptation to habitat

During the periodic dry fall of their habitat in the rhythm of the tides, the beach worm collects in water running off in damp and shady places and pulls the housing close to the ground. Especially on long dry periods the beach worm is well adapted by the closing of the case. In prolonged drought they can their housing with a horny lid, the operculum, it carries on the rear end of her foot, close. In this state, it can take three to four weeks without water coverage. Through a tiny gap the mouth of the screw can absorb oxygen from the air. The uptake of atmospheric oxygen can take place because of a special adaptation of the respiratory organs. The gills of the beach worm are in favor of the wall of the gill cavities that are heavily infiltrated with blood vessels, reduced. This adaptation allows not only the resistance to unstable weather conditions, but it is thus able to colonize an unrivaled habitat between land and sea. In the habitat above the mean high water line where only the waves and splashes for moisture care, other marine snails can not yet survive and land snails. In this zone you can only barnacles are dangerous, which settle on their shells. Through a thick armor of barnacles, the worms to be restricted in their freedom of movement and die.

Locomotion

The beach worm separates the front body through numerous glands a 0.5-1 cm wide strip of mucus on which it travels creeping. Together with the body impression, these bands can be seen as crawler lanes in soft sediments of tidal flats well.

Food

The beach worm is a non-selective grazers. With the radula diatoms and organic particles are grazed on the hard and soft floors. Even young seedlings of algae and the nauplii of barnacles eaten by the beach worm.

Reproduction

In their reproduction the beach worm is still strongly tied to the sea. The eggs are released at spring tide into the sea. The larvae make all developmental stages by in the water before they go ashore. Other Littorina species hatch directly from the eggs or even viviparous like the little beach snail ( Littorina saxatilis ).

Use

In France and parts of the British Isles beach snails are eaten as " Seafood ", see Snail (food)

Paleontology

As an index fossil in the area of ​​today's Baltic Sea led to the designation of Littorinameeres.