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The name snail applies to most members of the molluscan class Gastropoda that have coiled shells. Snails are found in freshwater, marine, and terrestrial environments. Most are of herbivorous nature, though a few land species and many marine species may be omnivores or carnivores. Other gastropods, which lack a conspicuous shell, are commonly called slugs, and are scattered throughout groups that primarily include snails. While most people are familiar with only terrestrial snails, the majority of snails are not terrestrial. Snails with lungs belong to the group Pulmonata, while those with gills form a paraphyletic group.
Physical characteristics
Snails move like earthworms by alternating body contractions with stretching, with a proverbially low speed (1 mm/s is a typical speed for adult helix lucorum ). They produce mucus in order to aid locomotion by reducing friction. The mucus also reduces the snail's risk of injury (snails can crawl over razor blades without injury) and helps keep away dangerous insects like ants. When retracted into their shells, snails secrete a special type of mucus which dries to cover the entrance of their shells with a 'trapdoor' like structure called an operculum. This is similar to some slug species which build a shell-like object below their upper skin to prevent drying out. The operculum of some snails has a pleasant scent when burned, so it is sometimes used as an ingredient in incense.
In winter or in dry seasons, some snail species hibernate in their shells by building an operculum for protection, and which is destroyed in spring or when their surroundings becomes wetter. Some species gather and hibernate in groups while others bury themselves before hibernating.
Snails come in a range of sizes. The largest land snail is the Giant African Snail (Achatina achatina; Family Achatinidae), which can measure up to 30 cm. Pomacea maculata (Family Ampullariidae), or Giant Apple Snail is the largest freshwater snail, with a diameter of up to 15 cm and a mass of over 600 g. The biggest of all snails is Syrinx aruanus, an Australian marine species which can grow up to 30 inches in length, and 40 pounds in weight.[http://www.g-kexoticfarms.com/funanimalfacts.html
The proportions of snail and nautilus shells are an example of the appearance of the golden ratio in nature. Patterns on shells of certain sea snails (Conus, Cymbiola) are similar to those formed by cellular automata.
As the snail grows, so does its shell. A snail will close off a section of its shell and add a new chamber as it grows, each chamber being larger than the previous one by a constant factor. As a result, the shells forms a logarithmic spiral. At some point, the snail builds a lip around the opening of the shell, stops growing, and begins reproducing.
The shells of snails and other molluscs, and snail egg casings, are primarily made up of calcium carbonate. Because of this, they need calcium in their diet and watery environment to produce a strong shell. A lack of calcium, or low pH in their surroundings, can cause thin, cracked, or perforated shells. Usually a snail can repair damage to its shell over time if its living conditions improve, but severe damage can be fatal.
Hibernation
Snails hibernate during the winter (typically October through April in the Northern Hemisphere). They may also aestivate in the summer in drought conditions. To stay moist during hibernation, they seal their shell opening with a dry layer of mucus called an epiphragm.
Reproduction
Some snails are hermaphrodites, producing both spermatozoa and ova. Others, such as Apple Snails, are either male or female. Prolific breeders, snails inseminate each other in pairs to internally fertilize their ova. Each brood may consist of up to 100 eggs.
Snails have small slits on their necks where fertilisation occurs and the eggs develop.
Garden snails bury their eggs in shallow topsoil primarily while the weather is warm and damp. After 2 to 4 weeks of favorable weather, these eggs hatch and the young emerge. Snails may lay eggs as often as once a month.
Predators
Snails have many natural predators, including members of all major vertebrate groups, decollate snails, ground beetles, and even the predatory caterpillar Hyposmocoma molluscivora.
Humans also pose great dangers to snails. Besides the obvious threat of stepping on them or putting salt on the fleshy body part, water pollution and acid rain destroy their shells and poison them, causing many species of snails to become extinct. In addition, snails are used as human food (often known as escargot) in Europe, Asia and Africa.
Lifespan
The lifespan of snails varies from species to species. In the wild, Achatinidae snails live around 5 to 7 years and Helix snails live about 2 to 3 years. Aquatic Apple Snails live only a year or so. Most deaths are due to predators or parasites. On occasions, snails have lived beyond this lifespan, up to 30 years or more.The Roman snail or escargot (Helix pomatia)
Snails as food
Snails are eaten as food in some parts of the world. Although escargot is the French word for "snail", escargot on an English menu is generally reserved for snails prepared with traditional French recipes (served in the shell with a garlic & parsley butter).
In Europe, three species, all from the genus Helix, are ordinarily eaten:
- Helix pomatia, the Edible snail, prepared in its shell, with parsley butter.
- Typical size: 40 to 55 mm for an adult weight of 25 to 45 g.
- Typically found: in Burgundy.
- Helix aspersa :
- Helix aspersa aspersa also known as the European brown snail, is cooked in many different ways, according to different local traditions.
- Typical size: 28 to 35 mm for an adult weight of 7 to 15 g.
- Typically found: Mediterranean countries (Europe and North Africa) and the French Atlantic coast.
- Helix aspersa maxima .
- Typical size 40 to 45 mm for an average weight of 20 to 30 g.
- Typically found: in North Africa.
- Helix aspersa aspersa also known as the European brown snail, is cooked in many different ways, according to different local traditions.
Achatina fulica, a giant African snail, is sliced and canned and passed off on some consumers as escargot.
Snails are also popular in Portugal, where they are called "caracóis" (Portuguese for "snails"), and served in cheap snack houses and taverns, usually boiled with garlic and oregano. Traditional Spanish cuisine is very fond of snails ("caracoles"), too, consuming several species such as Helix aspersa, Helix punctata, Helix pisana or Helix alonensis among others. Small to medium size varieties are usually cooked in several spicy sauces or even in soups, while the bigger ones may be reserved for other dishes such as the "arroz con conejo y caracoles" (a paella-style rice with snails and rabbit meat, very popular in the inner regions of south-eastern Spain) or the many local versions of gazpacho (also a typical meal of meat and vegetables with pieces of unleavened flour cakes).
Hélicicultures are snail farms. "In nature they almost everywhere are put under protection (at least the Roman snail must not be collected any more), but especially the Roman snail and the garden snail (Cornu aspersum) are cultivated on snail farms (Hélicicultures)."
Various snail species are also eaten in Asian cuisines as well.
Gallery
See also
References
External links
- The trail of the snail
- Snails kept in captivity as pets
- The World of Snails
- AppleSnail.Net
- Farming Roman Snails
- Snail eating snails
- Brown garden snail
- Molluscs
Gastropods | Molluscs | Snails
Schneck | Schnecken | caracol | Heliko | Escargot | Heliko | gliemezis | csiga | siput | カタツムリ | Slakken | Сæтæлæг | Caracol | etana | 蜗牛
"Snail"