AppearanceThe adult bears a hard, thin calcareous shell 25–40 mm in diameter and 25–35 mm high, with four or five whorls. The shell is variable in coloring and shade of color, but generally it has a reticulated pattern of dark brown, brownish-golden, or chestnut with yellow stripes, flecks, or streaks . The aperture is large and characteristically oblique, its margin in adults is whitish and reflected.
The body is soft and slimy, brownish-grey, and the animal retracts itself entirely into the shell when inactive or threatened. When injured or badly irritated the animal produces a defensive froth of mucus that might repel some enemies or overwhelm aggressive small ants or the like. It has no operculum; during dry or cold weather it seals the aperture of the shell with a thin membrane of dried mucus; the term for such a membrane is ''epiphragm''. The epiphragm helps the snail retain moisture and protects it from small predators such as some ants.
The snail's quiescent periods during heat and drought are known as aestivation; its quiescence during winter is known as overwintering. When overwintering, ''Cornu aspersum'' avoids the formation of ice in its tissues by altering the osmotic components of its blood ; this permits it to survive temperatures as low as -5 °C . During aestivation, the mantle collar has the ability to change its permeability to water. The snail also has an osmoregulatory mechanism that prevents excessive absorption of water during hibernation. These mechanisms allow ''Cornu aspersum'' to avoid either fatal desiccation or hydration during months of either kind of quiescence.
During times of activity the snail's head and "foot" or "belly" emerge. The head bears four tentacles; the upper two are larger and bear eye-like light sensors, and the lower two are tactile and olfactory sense organs. The snail extends the tentacles by internal pressure of body fluids, and retracts all four tentacles into the head by invagination when threatened or otherwise retreating into its shell. The mouth is located beneath the tentacles, and contains a chitinous radula with which the snail scrapes and manipulates food particles.
The shell of Cornu aspersum is almost always right-coiled, but exceptional left-coiled specimens are also known, see Jeremy for an example.
Distribution''Cornu aspersum'' is native to the Mediterranean region and Western Europe, from northwest Africa and Iberia, eastwards to Asia Minor, and northwards to the British Isles.
About the beginning of the 20th century, a number of North African endemic forms and subspecies were described on the basis of shell characteristics. The commonest subspecies, ''Cornu aspersum aspersum'' , has become very abundant, mainly in agricultural and residential human habitats where the climates is temperate, Mediterranean, or subtropical.
''Cornu aspersum'' is a typically anthropochorous species; it has been spread to many geographical regions by humans, either deliberately or accidentally. Nowadays it is cosmopolitan in temperate zones, and has become naturalised in many regions with climates that differ from the Mediterranean climate in which it evolved. It is present on all continents except Antarctica, and occurs on most major islands as well. Its passive anthropochory is the likeliest explanation for genetic resemblances between allopatric populations. Its anthropochorous spread may have started as early as during the Neolithic revolution some 8500 BP. Such anthropochory continues, sometimes resulting in locally catastrophic destruction of habitat or crops.
Its increasing non-native distribution includes other parts of Europe, such as Bohemia in the Czech Republic since 2008. It is present in Australia, New Zealand, North America and southern South America. It was introduced to Southern Africa as a food animal by Huguenots in the 18th century, and into California as a food animal in the 1850s; it is now a notorious agricultural pest in both regions, especially in citrus groves and vineyards. Many jurisdictions have quarantines for preventing the importation of the snail in plant matter.
BehaviorLike other Pulmonata, the individuals of the species ''Cornu aspersum'' are hermaphrodites, producing both male and female gametes. Reproduction is usually sexual, although self-fertilisation sometimes occurs. During a mating session of several hours, two snails exchange sperm. ''Cornu aspersum'' is one of the species that uses love darts during mating.
About two weeks after fertilisation, the snail lays a batch of about 80 spherical pearly-white eggs into crevices in the topsoil, or sheltered under stones or the like. In a year it may lay approximately six batches of eggs. The size of the egg is 4 mm.
The young snails take one to two years to reach maturity. In some regions snail farms produce these snails commercially.The snail secretes thixotropic adhesive mucus that permits locomotion by rhythmic waves of contraction passing forward within its muscular "foot". Starting from the rear, the contraction of the longitudinal muscle fibres above a small area of the film of mucus causes shear that liquefies the mucus, permitting the tip of the tail to move forward. The contracted muscle relaxes while its immediately anteriad transverse band of longitudinal fibres contract in their turn, repeating the process, which continues forward until it reaches the head. At that point the whole animal has moved forward by the length of the contraction of one of the bands of contraction. However, depending on the length of the animal, several bands of contraction can be in progress simultaneously, so that the resultant speed amounts to the speed imparted by a single wave, multiplied by the number of individual waves passing along simultaneously.
A separate type of wave motion that may be visible from the side enables the snail to conserve mucus when moving over a dry surface. It lifts its belly skin clear of the ground in arches, contacting only one to two thirds of the area it passes over. With suitable lighting the lifting may be seen from the side as illustrated, and the percentage of saving of mucus may be estimated from the area of wet mucus trail dabs that it leaves behind. This type of wave passes backwards at the speed of the snail's forward motion, therefore having a zero velocity with respect to the ground.
The snail moves at a top speed of 1.3 centimetres per second ,...hieroglyph snipped... and has a strong homing instinct, readily returning to a regular hibernation site.
In spite of its apparent slowness and limitations, the snail exploits the special nature of its mucus to achieve some startling feats. It can go up a slope at any angle, including upside down, resist being pulled off a firm surface with an adhesive strength several times its own weight, rest on a surface at any angle without any expenditure of energy, or, notoriously, climb a needle-like stem or pass over the edge of razor blade without harm, relying on the firmness of its mucus film in its shear-resistant phase.
Habitat''Cornu aspersum'' is a primarily a herbivore with a wide range of host plants. It feeds on numerous types of fruit trees, vegetable crops, rose bushes, garden flowers, and cereals. It also is an omnivorous scavenger that feeds on rotting plant material and on occasion will scavenge animal matter, such as crushed snails and worms. In turn it is a food source for many other animals, including small mammals, many bird species, lizards, frogs, centipedes, predatory insects such as glowworms in the family Lampyridae, and predatory terrestrial snails.
The species may on occasion be of use as an indicator of environmental pollution, because it deposits heavy metals, such as lead in its shell.
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