Land snails

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Land snails
Grove cepaea (Cepaea nemoralis)

Grove cepaea ( Cepaea nemoralis )

Trunk : Molluscs (mollusca)
Class : Snails (gastropoda)
Subclass : Orthogastropoda
Superordinate : Heterobranchia
Order : Lung snails (pulmonata)
Subordination : Land snails
Scientific name
A. Schmidt , 1855

The land snails (Stylommatophora, Greek for 'stalk eyes') are representatives of the lung snails that live permanently on land . From the freshwater aquatic snails , which have only one pair of antennae, they differ conspicuously by four (two pairs) handle-shaped antennae, of which the rear, longer pair has the eyes at the tip.

Breathing takes place through the lung cavities, the walls of which are very vascular. Land snails need a special water balance to protect them from dehydration. They produce large amounts of mucus that protects against excessive evaporation. In addition, a housing often provides additional protection. Nudibranchs, in which the shell is reduced, avoid exposure to the sun. But land snails can survive for a few days even with high water loss (50–80%). Some xerophilic species with thick limestone shells are even desert dwellers.



Construction of a snail housing from below

Like most snails, most land snails also have a shell. In addition to the evaporation protection already mentioned, this offers the snails protection from danger and the cold. In the event of danger, the land snail retreats into its housing. Since it does not have a lid, the opening is closed with a jacket bead. During longer periods of drought or cold, the snails close their shells with an epiphragma (lime seal). The snail shell corresponds to an external skeleton. It is already formed in the egg during development and consists of three layers, the outer conchiolin layer , followed by the lime and the third, inner mother-of-pearl layer . The lime layer is formed by special glands that are located on the edge of the mantle (regulate growth in size) and on the surface (regulate growth in thickness ). The housing is installed in the form of calcium carbonate . Their shell is curled up in a screw-like manner and rarely receded. In the last turn of the snail shell, especially in the opening, there are often teeth and various depressions.


The red slug is a slug

In nudibranchs, the shell has receded and is often still rudimentary . With them, the visceral sac is reduced, since the organs normally located in it are secondarily included again in the dorsal part of the head foot (cephalopodium). Like the respiratory opening, the genital opening in nudibranchs is always on the right.

Above all, the loss of the shell gave the slugs greater mobility.


Roman snail with retracted antennae

Land snails, unlike most other snails, are hermaphrodites . They lay up to 70 eggs, from which the young snails hatch after a few weeks.

The act of mating, using the Roman snail as an example: First, the snails touch each other with their antennae. Then they climb up each other. In order to stimulate the other person, the snails shoot a 5-10 mm long lime stiletto into their sole. The actual act of mating: the animal acting as a male injects a packet of semen into the sexual opening of the other. Now the snails separate again. Double fertilization rarely takes place. Then egg cells are produced in the hermaphroditic gland of the “female” (the “males” produce their semen there) and sent towards the semen packet. Now the eggs will be fertilized. A few days later the snail digs a hole in the earth and lays the eggs there. Small snails hatch from these eggs 2–6 weeks later. You have a transparent house because you have not yet been able to accumulate lime. They slip out of the cave and start to eat. The animals are sexually mature after about 3 years.

Paleontology and evolution

In addition to a few rather uncertain older finds at the end of the Paleozoic , which perhaps only represented external convergence formations, as well as assumed real Stylommatophora at the end of the Jurassic period, there are certain fossil representatives of various modern families of the Stylommatophora from the Upper Cretaceous ( Coniacium , approx. 88 million years ago) ). These are obviously members of the Streptaxidae , Camaenidae and Helminthoglyptidae families . In the next stage (the Santonium , about 85 million years ago) the families Subulinidae and Plectopylidae follow .


According to recent molecular biological studies by Wade, Mordan & Naggs (2006), the Stylommatophora are monophyletic. According to Bouchet & Rocroi (2005), they contain the following superfamilies and families:

Individual evidence

  1. ^ Noel Morris & John Taylor: Global events and biotic interactions as controls on the evolution of gastropods. In: Stephen J. Culver, Peter F. Rawson: Biotic response to global change: The last 145 million years . Cambridge University Press (2000)
  2. ^ MJ Benton (Ed.): The Fossil Record 2. Chapman & Hall, London 1993.
  3. ^ A b Fred G. Thompson, Edna Naranjo-García: Echinichidae, a new family of dart-bearing helicoid slugs from Mexico, with the description of a new genus and three new species (Gastropoda: Pulmonata: Xanthonychoidea) . Archives for Molluscology, 141 (2): 197-208. doi : 10.1127 / arch.moll / 1869-0963 / 141 / 197-208 . Preview (PDF; 385 kB)


  • Philippe Bouchet, Jean-Pierre Rocroi: Part 2. Working classification of the Gastropoda. In: Malacologia. , Volume 47, Ann Arbor 2005 ISSN  0076-2997 , pp. 239-283.
  • Christopher M. Wade, Peter B. Mordan, Fred Naggs: Evolutionary relationships among the Pulmonate land snails and slugs (Pulmonata, Stylommatophora). In: Biological Journal of the Linnean Society. Volume 87, Oxford 2006, ISSN  0024-4066 , pp. 593-610.
  • Wilfried Westheide, Reinhard Rieger (Hrsg.): Special zoology. Volume 1. Spectrum Academic Publishing House, 2003, ISBN 3-8274-1482-2 .

Web links

Commons : Stylommatophora  - collection of images, videos and audio files
  • Verena Eisfeller, Christoph Beckers: Mollusca. (PDF, 2.11 MB) In: Terrestrial ecological excursion by the Department of Biology, Cevennes 2002, TU Darmstadt. Archived from the original on February 12, 2007 ; Retrieved July 8, 2013 .