snails

Article

July 5, 2022

Snail (cochlea; kagyu) is a common name for snails that live on land and have shells. In particular, it is often the case that the shells of pulmonary species are not elongated.

Overview

The word "snail" is a vernacular and does not refer to a specific taxon, and there is no strict definition for biological classification as it spans many families. Of the land snails (abalones that live on land), those without shells are roughly called "slugs", and those with shells are called "snail", "denden beetle", "maimai", etc. In general, snails are pulmonary snails that do not have a lid and have eyes at the tip of their antennae, and often refer to those with spherical or bun-shaped shells. be. Cyclophoridae with a lid on the shell and Clausiliidae with an elongated shell are rarely called snails. However, as mentioned above, there is no strict definition, so all land snails with shells are sometimes called snails. In Japan, the snail family is a typical snail. In general, the mobility is small and it is difficult to spread the distribution beyond mountain ranges, arid areas, and water areas, so speciation is likely to occur in each region. Like other fauna, species tend to be more prevalent in the regions south of the north. Even in the Japanese archipelago, only a few species such as Acusta despectarum, which is also found in fields and around houses, and the exotic snail, Bradybaena macrois, have a wide distribution area, and other snails have different species depending on the region. It inhabits, and many species are interchanged in Kanto and Kansai. In addition, speciation is particularly likely to occur in isolated areas such as islands, and endemic species often evolve from island to island in the Nansei Islands and Ogasawara Islands. Such speciation is even more pronounced on a global scale and usually varies widely between continents at the family and genus level. . . .

Form

The only mollusks that live on land are abalone, but they are adapted to various environments and their morphology and ecology are differentiated. Some of them have degenerated shells such as slugs, and some have elongated shells such as Clausiliidae and Allopeas clavulin. The size is from about 1 mm to several cm in Japan, and Euhadra awaensis from Shikoku, which has a shell diameter of more than 60 mm, is the largest native species. In Africa and elsewhere, there are species such as Achatina achatina, whose shell is 20 cm or more and whose body length is close to 40 cm when stretched. Among the land snails, the family Cyclophoridae and Cyclophoridae have lids that close the shell, and these have different origins from the pulmonary species commonly called snails.

Body

The body is called the soft body part, and it is a muscle called the shell axis muscle (kakujikukin) that is attached to the shell axis part in the shell. This muscle contracts and pulls the body into the shell. The shell and the body are not different, the shell is one of the organs of the body, and there are internal organs inside. Therefore, if a snail comes out of its shell, it will not become a slug, and if the shell is severely damaged or forcibly removed, it will die. The same is true for other snails. The Stylommatophora Helicida (Stylommatophora), commonly called snails, has two pairs of large and small antennae on the head, and the tip of the large antennae (posterior antennae) has an eye. On the other hand, land snails of prosobranchia such as Cyclophoridae have only one pair of antennae, are pointed, and have eyes at the base. All snails can only live if their soft bodies are moist.