Most snails move by gliding along on their muscular foot, which is lubricated with mucus. Underside of a snail climbing a blade of grass, showing muscular foot. 1.4 Reproduction (primarily land snails)īiology (primarily of pulmonate land snails) Physical characteristics.1.3 Hibernation/Estivation (land snails).1 Biology (primarily of pulmonate land snails).Surprisingly, snails with lungs and with gills have diversified widely enough over geological time that numerous species using either form of respiration can be found on land, in freshwater and in the sea. Snails which have a lung belong to the group Pulmonata, while those with gills form a paraphyletic group, in other words snails with gills form a number of taxonomic groups that are not very closely related. Marine snails have much greater diversity, and a greater biomass. In other words, the reduction or loss of the shell has evolved many times independently, within several very different lineages of gastropods so slugs are not always closely related to one another.Īlthough the average person is perhaps more familiar with terrestrial snails, these terrestrial gastropods are in the minority. Taxonomic families of land slugs and shell-less sea slugs occur within various larger taxonomic groups of shelled species. Thus even a fairly large slug can take advantage of certain habitats with very little space, such as under bark on trees, or under stone slabs lying on the ground. 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 is really no difference between a slug and a snail, except that a shell-less animal is much more manouverable. Many snails are herbivorous, though a few land species and many marine species are omnivores or predatory carnivores. Snails in the wider sense of the word can be found in a huge range of different environments: the great majority are marine, many are terrestrial, and numerous kinds can be found in freshwater, and even brackish water. In many parts of the world, the edible species Helix aspersa or Cornu aspersum, has been introduced, and has become a pest in farms and gardens, so this is perhaps a good example of a species commonly known as "the snail." Whichever reasonably large land snail species is most commonly seen or most commonly eaten in a given area, that species will usually be referred to simply as "snails" by the local people. However, certain species are "anthropophilic", which means they are found most often around human habitation. Species of land snails live in almost every kind of habitat, from deserts and mountains, to marshes, woodland, and gardens. The word "snail" is also applied more specifically to various larger species of pulmonate land snails. In other words it is extremely hard to generalize accurately about "snails" in the wider sense of the word. Because of this, snails are extraordinarily diverse, in habitat, in form, in behaviour and in anatomy, and therefore what is true of one snail species may not at all be true of another, more distantly related one. The class Gastropoda is the second largest class of invertebrates, second only to the insects.
The word snail is loosely applied to almost all members of the molluscan class Gastropoda which have coiled shells in the adult stage.