Mouse ears

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Mouse ears
Mouse ears (Myosotella myosotis)

Mouse ears ( Myosotella myosotis )

Systematics
Order : Lung snails (pulmonata)
Superfamily : Ellobioidea
Family : Coastal snails (Ellobiidae)
Subfamily : Pythiinae
Genre : Myosotella
Type : Mouse ears
Scientific name
Myosotella myosotis
( Draparnaud , 1801)

The mouse ear snail ( Myosotella myosotis ), also known as the mouse ear snail, is a species of snail belonging to the coastal snail family (Ellobiidae). In Europe it lives in coastal salt marshes from Great Britain and Denmark to the Mediterranean and Black Sea . The salt marshes of the German coasts are a globally unique habitat with specific environmental conditions. The mouse ear is adapted to this habitat and was named mollusk of the year in Germany in 2008 .

features

The case measures 5 to 11 mm in height and is 3 to 5 mm wide. It is elongated egg-shaped, right-handed with a tapered thread. The partly shiny color is brownish to yellowish. The mouth (housing opening) is also pointed and egg-shaped, the spindle (mouth part on the housing axis) has two folds that spiral into the interior of the housing. The upper turns of the 6-8 whorls are only slightly convex and separated by a flat suture , also called a seam, finely striped and sometimes have fine hairs. The mouth edge is thickened on the inside as a so-called lip and slightly widened outwards like a brim. On salt-rich coasts, such as the North Sea , the housing is thicker, larger and longer than in regions with less salt, such as the Baltic Sea .

The body is beige to light gray, with the top of the front body and the area of ​​the antennae being a little darker. The small dark eyes are at the base of the antennae. This distinguishes the coastal snail from most gill snails , whose eyes are almost always on the outside of the antennae base, and from most other terrestrial lung snails , whose eyes are located at the end of the antennae. The mouse ear has only two antennae, which is another difference to almost all more highly developed land lung snails, as these have a pair of smaller antennae in the lower part of the head in addition to the two eye-antennae . The radula has a central tooth, about 10 posterior teeth and 20 marginal teeth in the semi-transverse row.

Similar species

The closely related species Myosotella denticulata (Montagu, 1803) has a very similar housing, but the edge of the mouth is serrated.

Habitat and Distribution

Mouse ears live mainly in the grassy area of ​​the salt marshes directly on the coast with little tidal effect. They sit under driftwood , stones , rotting seaweed , on plants or washed-up planks and stay in the muddy soil. Preferred habitats are the edges of small bodies of water in the salt marshes. In Germany, mouse ears are only found on salt marshes. They are quite tolerant of the salt content ( salinity ) in their habitat. Mouse ears can survive values ​​between 0.9 and 9.9% over long periods of time, with a salt content of 1.8% being found to be ideal. Diatoms and decaying organic materials ( detritus ) are the main sources of food .

Mouse ears are common on the North and Baltic Sea coasts, the coasts of Europe between Denmark, Great Britain and the Mediterranean. They were also abducted to the east coast of North America , South America (Peru), South Africa and Jamaica and have established themselves there.

Reproduction and development

Mouse ears have both male and female sex organs and are therefore referred to as hermaphrodites . In terms of time, the male sexual organs become functional before the female organs. Only from the age of two, when both sex organs are functional, can these animals mate both as males and females . The pairings usually take place in April / May and August / September. When mating, however, one partner usually acts as a female and the other partner as a male. Mating with three animals has also been observed, with the middle animal functioning as both a female and a male. The fertilized eggs are laid as a package, usually 25 to 30 eggs (rarely only 15, at most up to 80 eggs) in damp crevices or in dug caves (10-15 mm deep).

The development time of the embryos can vary greatly depending on the temperature, it is between 3 and 7 weeks. In the egg shell, the embryos go through a Veliger stage with initially a left-hand winding housing, a colored mid-gland and a sealing lid. The operculum is lost in the egg in the further course of development. They hatch from the egg as small finished animals. Under laboratory conditions, mouse ears with a housing height of 5 mm became sexually mature just eight weeks after hatching. The average lifespan is 3 to 4 years. In order to survive the winter , the snails band together in groups and hibernate in small burrows in the ground.

Danger

In northern Germany is Myosotella myosotis from extinction threatened. The reason is the increasing destruction of the salt marshes, which are the exclusive habitat of snails in northern Germany.

supporting documents

literature

  • Gert Lindner: Shells and snails of the world's oceans, appearance, occurrence, systematics , BLV Verlagsgesellschaft mbH, BLV, Munich, Vienna, Zurich 1999, ISBN 3-405-15438-3
  • Michael P. Kerney, Robert AD Cameron, Jürgen .H. Jungbluth: The land snails of Northern and Central Europe . Paul Parey Publishing House, Hamburg, Berlin 1983, ISBN 3-490-17918-8
  • Vollrath Wiese: Germany's land snails. 352 pp., Quelle & Meyer, Wiebelsheim 2014 ISBN 978-3-494-01551-4 (p. 35)
  • Rainer Willmann: Mussels of the North and Baltic Seas , Verlag J. Neumann-Neudamm GmbH & Co.KG 1989, ISBN 3-7888-0555-2
  • David Geyer: Our land and freshwater mollusks . XI + 224 pp., 3rd, completely reworked. Edition KG Lutz-Verlag, Stuttgart 1927.

On-line

Individual evidence

  1. Gil Rilov, Jeffrey A. Crooks (Eds.): Biological invasions in marine ecosystems: ecological, management, and geographic perspectives. XXVI, 641 S., Berlin, u. a., Springer, 2009 ISBN 978-3-540-79235-2 Preview on Google Books
  2. ^ DG Herbert: Myosotella myosotis (Mollusca: Ellobiidae) - an overlooked, but well-established introduced species in South Africa. African Journal of Marine Science, 34 (3): 459-464, doi : 10.2989 / 1814232X.2012.716374

Web links

Commons : Mouse ears  - collection of images