Snail

The term snail applies to the majority of the terrestrial Mollusque S with shell of the class of the Gastéropode S, whatever their size (some measure hardly 2 mm) or their form, like with certain watery gastropods the such Planorbe S, often called " snails nettoyeurs" by the amateurs of Aquariophilie.

The majority of snails are Phytophage S, though some species are Omnivore S or Zoophage S or Détritivore S.

The difference between snail and Limace S is not always obvious. Thus, certain testacelles slugs as the are equipped with a rudimentary shell but quite visible, whereas the snails of the family of the Vitrinidae , for example, have only one incomplete shell in which the animal cannot generally withdraw itself completely.

Description

The snails have one or two pairs of retractile Tentacule S.

The first pair shelters the Yeux (little used) in its upper part and an olfactive bulb under the eye. The second pair is an olfactive and tactile body (epithelium) very much used.

The edge located at the opening of the shell is called " Peristome ". The shape, the thickness and the color of the peristome often have a great importance in the identification of the species of gastropods.

Whatever its pace, the shell of snail is always helicoid

Displacement

The snail moves, only forwards, thanks to its foot, which is in fact gigantic a Muscle which contracts and lengthens alternatively. 1 m/s is 6 cm/min is the mean velocity of a adult Helix lucorum . Glands secrete also various types of Mucus (its " bave") container of many compounds (Allantoïne, Collagène, elastin) which at the same time enable him to advance more easily while slipping on the obstacles and to fix itself even vertically on certain walls. Mucus is also used with snail to get rid of certain substances like heavy metals, and between also in the composition of the shell. Mucus is thick, it hardens and dry in contact with the air by leaving a brilliant trail to the light.

Food

The snails feed thanks to a named toothed language Radula. The language of snail is covered with very hard asperities, laid out in regular lines, as the grater of the carpenter.

The food of snails varies according to their species. Certain snails are phytophagous, détritivores, the other necrophagous ones, others finally predatory, sometimes cannibals. The snail ( Horned aspersum or Cepaea sp. ) can attack the crop plants of the gardens and is thus generally regarded as a harmful Organization. The phytophagous snails lodge in their intestine a total colony count which takes part in the digestion of the plants. The bacteria are maintained in life during the estivation or the hibernation, by nourishing mucus which is secreted by the intestinal epithelium.

Longevity

The lifespan of snails varies according to the species. In nature, the Achatinidae live from 5 to 7 years whereas the Helix seldom exceed the 3 years age. Their death must often with Prédateur S or Parasite S.

In captivity, their longevity is much longer and goes from 10 to 15 years for the majority of the species. Certain snails lived more than thirty years.

Hibernation of terrestrial snails

The terrestrial snails are active only when moisture is sufficiently high. In the contrary case, the animal retracts inside its shell which it seals by a mucous veil (short inactivity) or by a épiphragme (long inactivity like estivation, hibernation), which avoids dehydration to him. The photoperiod and the temperature are seasonal variables which induce the states of inactivity. Hibernation and/or estivation are answers to foreseeable environmental stresses. Each species presents a strategy adapted to resist these stresses.

The épiphragme is a stopper of mucus, more or less impregnated of limestone, which hardens while drying.

Environment

The snails can to some extent reflect the quality of their Environnement while accumulating in their flesh or their shell some Polluant S or Toxique S present in their medium. Their Mucus in particular protects them from the external, bacterial and fungic aggressions. It contributes to their thermal regulation. As this mucus is rich in sialic Acide, the target of the virus grippal, the question was posed of their capacity to shelter part of the cycle of the virus grippal whose target is the acid sialic.

The terrestrial snails are very sensitive to the parameters thermohygrometric and seem also sensitive to the luminous Pollution which can put out of order their system chronobiologic and disturb the phases of estivation (photo opposite) or hibernation.

The snails disappeared from most of the agricultural territories cultivated because of the Pesticide S. the network of the woodlands enables them to better survive, and one can hope that the enherbées Bandes made recently obligatory on certain surfaces to Europe can increase their chances of survival in the cultivated mediums.

Use

Food

In France four species are usually consumed:
  • Helix aspersa :
    • the Small-Gray ( Helix aspersa aspersa ), with more various and often local receipts, a size from 28 to 35 mm for an adult weight from 7 to 15 G. Present in the countries the Mediterranean NS (Europe and North Africa) and the French Atlantic facade.
    • the Large-Gray ( Helix aspersa maximum ), size from 40 to 45 mm for an adult weight from 20 to 30 G, present in North Africa.

  • the Snail of Burgundy ( Helix pomatia ), traditionally prepared in shell, with the garlic and parsley butter. Cut from 40 to 55 mm for an adult weight from 25 to 45 G. Natural geographical distribution: Central Europe

  • One gives sometimes the name of snail of sea to the Bigorneau, mollusc marine of close appearance.

The breeding (Héliciculture) gives acceptable results under the current economic conditions. It relates to mainly Helix aspersa . The place where the snails rise is called a escargotière, but it is also the name of the dish specific, dug small cavities to put snails at the furnace and to serve them.

The statutory texts of the European Community do not regard terrestrial snail as a Mollusque. It does not return either in the legal definition of Viande

Cosmetic

The snails are sometimes high to recover their mucus which is used in industry Cosmétique.

Predatory

The snails are an important component of the trophic networks. They have the many predatory ones, birds or mammals in particular. There exists even a raptor, the Milan of the marshes whose nearly exclusive food is made up large South American watery snails of the family of the Ampullariidae , of which primarily Pomacea bridgesii .

Other species

Here an not-exhaustive list of other species:

Neurology

The snail, like many other molluscs, has Neuron S giants allowing the intracellular electrode installation of largely used in neurological research for better including/understanding the operating process of the human neurons.

References

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