Snail

:Further reading: Gastropoda

Snail is a common name for almost all members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in a general sense, it includes sea snails, land snails and freshwater snails. Otherwise snail-like creatures that lack a shell (or have only a very small one) are called slugs.

One species of land snail, the Giant African Snail, can grow to be from snout to tail, and weigh . The largest living species of sea snail is Syrinx aruanus which has a shell that can measure up to in length, and the whole animal with the shell can weigh up to .

Snails can be found in a very wide range of environments including ditches, deserts, and the abyssal depths of the sea. Although many people are familiar with terrestrial snails, land snails are in the minority. Marine snails constitute the majority of snail species, and have much greater diversity and a greater biomass. Numerous kinds of snail can also be found in fresh waters. Many snails are herbivorous, though a few land species and many marine species are omnivores or predatory carnivores.

Snails that respire using a lung belong to the group Pulmonata, while those with gills form a paraphyletic group; in other words, snails with gills are divided into a number of taxonomic groups that are not very closely related. Snails with lungs and with gills have diversified widely enough over geological time that a few species with gills can be found on land, numerous species with a lung can be found in freshwater, and a few species with a lung can be found in the sea.

Most snails have thousands of microscopic tooth-like structures located on a ribbon-like tongue called a radula. The radula works like a file, ripping the food into small pieces.

Types of snails by habitat

Slugs

Gastropod species which lack a conspicuous shell are commonly called slugs rather than snails, although, other than having a reduced shell or no shell at all, there are really no appreciable differences between a slug and a snail except in habitat and behavior. A shell-less animal is much more maneuverable and compressible, and thus even quite large land slugs can take advantage of habitats or retreats with very little space, squeezing themselves into places that would be inaccessible to a similar-sized snail, such as under loose bark on trees or under stone slabs, logs or wooden boards lying on the ground.

Taxonomic families of land slugs and sea slugs occur within numerous larger taxonomic groups of shelled species. In other words, the reduction or loss of the shell has evolved many times independently within several very different lineages of gastropods, thus the various families of slugs are very often not closely related to one another.

Snails in cuisine

Snails provide an easily harvested source of protein to many people around the world. Land snails, freshwater snails and sea snails are all eaten in various different countries (principally Spain, France, Italy, Portugal, Greece, Belgium, Laos, Cambodia and parts of the U.S.A.).

Agriculture

Cultural depictions

One expert, Professor Ronald Chase of McGill University in Montreal, has suggested that the ancient myth of Cupid's arrows might be based on early observations of the love dart behavior of the land snail species Helix aspersa.

In contemporary speech, the expression "a snail's pace" is often used to describe a slow, inefficient process.

The phrase "snail mail" is used to mean regular postal service delivery of paper messages as opposed to the delivery of E-mail or electronic mail, which is virtually instantaneous.

See also

References

External links

Category:Gastropods Category:Pet molluscs