Theba pisana, common names the white garden snail, the sand hill snail, white Italian snail, the Mediterranean coastal snail, or simply the Mediterranean snail, is an edible species of mediumsized air-breathing land snail, a pulmonate gastropod mollusk in the family Helicidae.
It is native to Mediterranean region, but it is an widespread invasive species in other countries. Theba pisana is a well-known agricultural pest in many parts of the world. It has a shell from white to yellow-brown with light brown spiral markings.
Distribution:
The species is native to the Mediterranean region. The type locality is Italy. The distribution of Theba pisana includes the Mediterranean region and adjacent Atlantic coasts from central Morocco to north western Europe:
- Morocco
- Portugal
- In Spain occasionally also in the interior.
It is introduced to Minorca.
- A subspecies Theba pisana arietina from coastal habitats in Spain is on the Red List as Endangered.
- Italy
- Malta
- Greece
- Israel
- Egypt
- Belgium
- central Atlantic islands
The species has been introduced to numerous other areas, including:
- southwestern England and south Wales, Great Britain:
- introduced since at least the 1700s
- eastern and southern Ireland - introduced since at least the 1700s and it is still spreading along frost-free coastal localities.
- Netherlands - non-indigenous
- the USA in California
- parts of Africa
- Asia
- southeastern Australia, Tasmania
- South Africa
- It was introduced into South Africa prior to 1881. It has invaded the fynbos biome in South Africa. Given the very high densities that Theba pisana can attain at some sites, plus their apparently catholic feeding habits, their potential impact on the vegetation is cause for concern and should be further investigated.
In many of these places T. pisana has become a problematic invasive species and a serious agricultural pest. This species is already established in the USA, and is considered to represent a potentially serious threat as a pest, an invasive species which could negatively affect agriculture, natural ecosystems, human health or commerce. Therefore it has been suggested that this species be given top national quarantine significance in the USA.
Description:
Apical and apertural view of a shell, with an arrow marking the half-colvered umbilicus Theba pisana The shell background color is a creamy white. Different individuals may have shells with varying degrees of pale to dark brown markings. The markings, when present, may be in the form of uninterrupted spiral bands, spiral dotted lines, or small radial smudges.
The shell can be found in various colour variants, but is basically yellow or white with dark colour bands or spots and often a dark bluish grey apex. The shells of juveniles are sharply keeled,however the keel is not present on the final adult whorl.
The aperture often has a lip that is light reddish on the inside, and the lip margin is only reflected at columellar side. The umbilicus is narrow and half covered by the reflected columellar margin. The apex has a characteristic size in the eastern Mediterranean when compared with other species, where there are no other Theba species.
The umbilicus is also rarely seen in other species. Juveniles of Eobania vermiculata have a considerably larger apex. The width of the shell is 12-25 mm, but in Greece the adult shells are usually below 15 mm in width.
The height of the shell is 9-20 mm. The visible soft parts are very light yellowish with dark colour bands running from the sides to the upper tentacles; the tentacles are very long. This snail is sometimes confused with Cernuella virgata, a species with a much smaller and less inflated shell.
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