Snail

? Snails
Scientific classification
Kingdom: Animalia Subkingdom: Metazoa Phylum: Mollusca Class: Gastropoda

The name snail applies to most members of the molluscan class Gastropoda that have coiled shells. Other gastropods, which lack a conspicuous shell, are commonly called slugs, and are scattered throughout groups that primarily include snails. Snails are found in freshwater, marine, and terrestrial environments. 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. They produce mucus in order to aid locomotion by reducing friction. The mucus also reduces the snail's risk of injury and helps keep away potentially dangerous insects like ants. When retracted into their shells, snails secretes 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 taken and used as an ingredient in incense.

In winter or in dry seasons, some snail species hibernate in their shells by building the operculum, which they build only for the purpose of protection while hibernating and are destroyed in spring or when their surroundings becomes wetter. Some species would gather and hibernate in groups while others would bury themselves before hibernating.

Snails come in a range of different 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 its size reaching 15 cm diameter and over 600 g weight. The biggest of all snails is Syrinx aruanus, a marine species living in Australia. Shell lengths up to 1 m have been reported.

Snail shells, like those of the Nautilus, are one example of the appearance of the phi, the golden ratio, in nature. Patterns on shells of certain sea snails ( Conus, Cymbiola) are formed by biological version of cellular automata.

As the snail grows, so do their shells. A snail will close off a section of their shell and add a new chamber as it grows larger, each chamber being larger than the previous one by a constant factor. As a result, the shells forms a logarithmic spiral. At some point, a snail would build a lip around the opening of their shell, and when that happens, they would stop growing and start spending their energy and effort reproducing.

Snail shells and egg casings are made up of primarily calcium carbonate like other mollusk's shells. Because of this, they require a decent amount of calcium in their diet and watery environment to produce a strong shell. A lack of calcium, or if the pH level of their surrounding starts fluctuating, would likely cause their shells to be thin, crack, or have holes. Usually a snail can repair its shell damage over time if their living conditions improve, but some damage could be severe enough to be fatal for the snail.

Habitat

As one of the largest classes of animals, snails can be found throughout the world. They are found in freshwater, marine, and terrestrial environments. The majority of the world's snails live in the oceans and new species are being discovered regularly. Terrestrial snails prefer damp areas around vegetation, which they can use for cover during the day. Certain snails would hibernate during dry weather periods by hiding in their shells for extended periods of time.

Diet

A snail's diet varies by species. Terrestrial snails such as garden snails generally eat young plant shoots or bark, algea, moss, or decaying vegetative matter. Carnivorous snails, such as the Decollate Snail feed on other snails. Snails eat by using their radula, or scraping tongue, to shear their food.

Reproduction

Some snails are hermaphrodites, producing both spermatozoa and ova. Others, such as Apple Snails, are either male or female. Prolific breeders, snails in pairs inseminate each other to internally fertilize their ova. Each brood may consist of up to 100 eggs.

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 ground beetles, snakes, toads, turtles, and birds like chickens, ducks and geese, and even a predatory caterpillar.

Humans also pose great dangers to snails. Besides the obvious threat of being stepped on or having salt put on the fleshy body part. Water pollution and acid rain destroys their shells and poisons them, causing many species of snails to go extinct. In addition, snails are widely 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.

Control (garden pests)

Terrestrial snails and slugs are generally both migratory and nocturnal, thus difficult to control. Common methods of control include shallow dishes filled with beer, and the use of molluscicides.

A more crude, if effective, approach is to sprinkle salt on snails and slugs, which dehydrates their bodies and poisons them. However, this is not generally recommended as too much salt can be harmful to gardening plants.

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.

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.

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. 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 unlevened 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.