Classification, Anatomical and Biological Information
Due to an increase in commercial activity and the culinary interest in snails, biological and physiological studies of snails for consumption are now carried out by universities in Italy and in other countries. Studying special sensors and functions of snails has opened new paths in human research too. Snails have always been the prey of numerous species but their features and ability to adapt through simple but decisive changes have enabled them to survive. The most recent research projects build on those conducted by the French Duverney, Defrance, Meisenhimer, Cadart and Lesourd, the German Nietzke and the Italian Spallanzani.
As the Latin root of the name suggests (mollis, standing for "soft"). Mollusca are organisms with soft boneless bodies. Their body is sack-shaped containing internal organs.
The etymology of the word (in Greek gastèr stands for "belly", pus for "foot") perfectly describes the peculiarity of these little animals: they crawl using their muscled belly.
The ability to breed on land has enabled some Gastropoda to adapt and live on land, differentiating them from Mollusca living in water.
From ancient Greek: animals with eyes on the tip of their tentacles.
Helicidae have an external spiral shell to protect them (Helix).
The shell differentiates them from other snails. This external protection is made of calcium secretions produced by the mantel and is a very complex structure. It can be described as a cone-shaped tube winded around a spiral axis (columellar axis). The winding is usually clockwise, but there are also rare cases of anticlockwise winding. Helix Aspersa's columellar axis is full, while Helix Pomatia's is empty and features an internal columellar cavity. The rut between whorls is called suture. It starts from the apex and ends at the aperture (lips), which is surrounded by an edge called peristoma. In adult snails, the mantel protrudes outside the peristoma and calcifies around it. This is the easiest way to determine whether a snail is ready for reproduction. According to the species shells can show different colours and in some cases bright and dark stripes from the apex to the lips. The lines of growth are perpendicular to the whorls. The shell consists 97% of a chemical compound (aragonite) affine with calcium carbonate and 3% of other organic substances.
Apart from the shell, snails’ bodies can be divided into three other parts: head, foot and visceral sac.
The head is on the anterior part of the body and comprises one mouth and four retractable tentacles. The upper tentacles are longer and feature two small black spheres on their tip. These small eyes are not able to see properly but can distinguish colours and source of lights. The shorter tentacles are tactile organs, which together with the extremely high number of sensory cells on the skin, enable snails to perceive the outer world. The mouth is made up of two lips (outer and inner lip) and of two lateral cheeks. The genital opening is on the right side of the mouth.
The foot is the lower part of the body and it stays out of the shell when snails are in activity. It is covered by a series of elongated tubercles, a mass of muscles able to move the whole body thanks to a series of contractions of the traversal muscles and the production of slime.
The mantel is the upper part and generates the shell. It folds, forming the parallel cavity (the snail's lung) which enables breeding by opening and closing the pneumostoma. The central part is made up of a U-shaped digestive system, which starts from the mouth to the last whorl and ends with the anus.
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