Theba pisana
Encyclopedia
Theba pisana, common name
s 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 medium-sized 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.
The distribution of Theba pisana includes the Mediterranean region and adjacent Atlantic coasts from central Morocco to north western Europe:
The species has been introduced to numerous other areas, including:
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.
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 color 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.
Theba pisana usually lives in coastlands, in or near sandy habitats. In hot climates it aestivates often directly exposed to the sun, attached to grasses, shrubs or succulent plants, fence posts, tall weeds, and so on. It is common near beaches. In dunes it can live on nearly bare sand poorly fixed by grasses. In the north the snails do not estivate but they climb on plants in dry weather. It does not survive serious winter frosts.
Theba pisana is often associated with Cochlicella acuta
and Cernuella virgata
, but it can live slightly deeper inside pure sandy habitats and is usually more common than Cochlicella acuta. It is one of the most common snails in coastal regions from south Portugal to Greece.
Snails were most abundant along roadsides and densities decreased dramatically with distance from roads in the South Africa.
Snails were observed on a wide variety of endemic and introduced plant species and appeared to have a catholic diet. Theba pisana is also a significant pest of citrus, vines, legume crops and cereals in South Africa. In Australia, it feeds on a range of agricultural plants.
Theba pisana in Britain and France have an annual
life cycle and breed in summer and autumn, while in the Mediterranean, they have a biennial
life cycle with breeding in autumn and winter. Theba pisana appear to have an annual lifecycle, breeding in autumn to winter and growing to adult size of about 14 mm diameter by the end of the following summer in the South Africa. Maturity is reached at half maximum shell size after 1 year. Maximum shell size is attained after 2 years. This species of snail makes and uses love darts. The size of the egg is 2.2 mm. The population density
can reach up to 300-700 snails m² in South Africa.
They are active mostly at night and especially during periods of high humidity, irrespective of temperature in the South Africa.
Theba pisana is an intermediate host for the terrestrial trematode parasite Brachylaima cribbi
.
It uses the stalks of cereals as aestivating sites, which in turn clogs machinery and fouls produce during mechanical harvesting.
According to Quick (1952) Theba pisana has been responsible for the extermination of native snail species as a result of competition
for available food.
In their report on the status and potential impacts of alien invasive organisms in the fynbos
biome, MacDonald & Jarman (1984) predicted that Theba pisana would have very little impact on ecosystem
processes, such as nutrient cycling, energy flow and sediment dynamics or on the germination and succession processes of the plant community itself. However, the snail could seriously impact directly on fynbos plants, by feeding on them, and also displace native herbivores by competing with them for resources, and these effects have not been studied.
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s 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 medium-sized air-breathing land snail
Land snail
A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...
, a pulmonate gastropod mollusk in the family Helicidae
Helicidae
The Helicidae, sometimes known as the typical snails, are a taxonomic family of small to large, air-breathing, land snails. In other words, they are terrestrial pulmonate gastropod mollusks....
. It is native to Mediterranean region, but it is an widespread invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
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 MinorcaMinorcaMin Orca or Menorca is one of the Balearic Islands located in the Mediterranean Sea belonging to Spain. It takes its name from being smaller than the nearby island of Majorca....
. - 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 CaliforniaCaliforniaCalifornia is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
- parts of AfricaAfricaAfrica is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
- AsiaAsiaAsia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
- southeastern AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, TasmaniaTasmaniaTasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart... - South Africa - It was introduced into South Africa prior to 1881. It has invaded the fynbosFynbosFynbos is the natural shrubland or heathland vegetation occurring in a small belt of the Western Cape of South Africa, mainly in winter rainfall coastal and mountainous areas with a Mediterranean climate...
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
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
which could negatively affect agriculture, natural ecosystems, human health or commerce. Therefore it has been suggested that this species be given top national quarantine
Quarantine
Quarantine is compulsory isolation, typically to contain the spread of something considered dangerous, often but not always disease. The word comes from the Italian quarantena, meaning forty-day period....
significance in the USA.
Description
The shell
Gastropod shell
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
can be found in various colour variants, but is basically yellow or white with dark color 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
Aperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....
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
Apex (mollusc)
Apex is an anatomical term for the tip of the mollusc shell of a gastropod, scaphopod, or cephalopod mollusc.-Gastropods:The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod...
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
Eobania vermiculata
Eobania vermiculata also known as Helix vermiculata, common name the "chocolate-band snail" is a species of large, air-breathing, land snail, a terrestrial pulmonate gastropod mollusk in the family Helicidae, the true snails or typical snails....
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
Cernuella virgata
Cernuella virgata, also known as Helicella virgata, common name, the "vineyard snail", is a species of small, air-breathing land snail, a pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies....
, a species with a much smaller and less inflated shell.
Ecology
Theba pisana is often associated with Cochlicella acuta
Cochlicella acuta
Cochlicella acuta, common name the pointed snail, is a species of small but very high-spired, air-breathing land snail, a pulmonate gastropod mollusk in the family Cochlicellidae....
and Cernuella virgata
Cernuella virgata
Cernuella virgata, also known as Helicella virgata, common name, the "vineyard snail", is a species of small, air-breathing land snail, a pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies....
, but it can live slightly deeper inside pure sandy habitats and is usually more common than Cochlicella acuta. It is one of the most common snails in coastal regions from south Portugal to Greece.
Snails were most abundant along roadsides and densities decreased dramatically with distance from roads in the South Africa.
Snails were observed on a wide variety of endemic and introduced plant species and appeared to have a catholic diet. Theba pisana is also a significant pest of citrus, vines, legume crops and cereals in South Africa. In Australia, it feeds on a range of agricultural plants.
Theba pisana in Britain and France have an annual
Annual plant
An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...
life cycle and breed in summer and autumn, while in the Mediterranean, they have a biennial
Biennial plant
A biennial plant is a flowering plant that takes two years to complete its biological lifecycle. In the first year the plant grows leaves, stems, and roots , then it enters a period of dormancy over the colder months. Usually the stem remains very short and the leaves are low to the ground, forming...
life cycle with breeding in autumn and winter. Theba pisana appear to have an annual lifecycle, breeding in autumn to winter and growing to adult size of about 14 mm diameter by the end of the following summer in the South Africa. Maturity is reached at half maximum shell size after 1 year. Maximum shell size is attained after 2 years. This species of snail makes and uses love darts. The size of the egg is 2.2 mm. The population density
Population density
Population density is a measurement of population per unit area or unit volume. It is frequently applied to living organisms, and particularly to humans...
can reach up to 300-700 snails m² in South Africa.
They are active mostly at night and especially during periods of high humidity, irrespective of temperature in the South Africa.
Theba pisana is an intermediate host for the terrestrial trematode parasite Brachylaima cribbi
Brachylaima cribbi
Brachylaima cribbi is a species of terrestrial trematode parasite in family Brachylaimidae.- Overview :Intermediate hosts for Brachylaima cribbi are terrestrial snails Cochlicella acuta, Cernuella virgata and Theba pisana....
.
Impact of invasions
In addition to the direct negative effect of Theba pisana feeding on agricultural crops, it also has several other additional effects.It uses the stalks of cereals as aestivating sites, which in turn clogs machinery and fouls produce during mechanical harvesting.
According to Quick (1952) Theba pisana has been responsible for the extermination of native snail species as a result of competition
Competition (biology)
Competition is an interaction between organisms or species, in which the fitness of one is lowered by the presence of another. Limited supply of at least one resource used by both is required. Competition both within and between species is an important topic in ecology, especially community ecology...
for available food.
In their report on the status and potential impacts of alien invasive organisms in the fynbos
Fynbos
Fynbos is the natural shrubland or heathland vegetation occurring in a small belt of the Western Cape of South Africa, mainly in winter rainfall coastal and mountainous areas with a Mediterranean climate...
biome, MacDonald & Jarman (1984) predicted that Theba pisana would have very little impact on ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
processes, such as nutrient cycling, energy flow and sediment dynamics or on the germination and succession processes of the plant community itself. However, the snail could seriously impact directly on fynbos plants, by feeding on them, and also displace native herbivores by competing with them for resources, and these effects have not been studied.
Further reading
- Baker G. H. & Hawke B. G. (1990). "Life History and Population Dynamics of Theba pisana (Mollusca: Helicidae) in a Cereal-Pasture Rotation". Journal of Applied EcologyJournal of Applied EcologyThe Journal of Applied Ecology is a peer-reviewed scientific journal publishing research in all areas of environmental management. It began publication in 1964 and is the third oldest journal of the British Ecological Society...
27(1): 16-29. JSTOR. - Baker G. H. & Vogelzang B. K. (1988). "Life-history, population dynamics and polymorphism of Theba pisana (Mollusca: Helicidae) in Australia". Journal of Applied EcologyJournal of Applied EcologyThe Journal of Applied Ecology is a peer-reviewed scientific journal publishing research in all areas of environmental management. It began publication in 1964 and is the third oldest journal of the British Ecological Society...
25(3): 867-887. JSTOR. - Cowie R. H. (1985). "Microhabitat choice and high temperature tolerance in the land snail Theba pisana (Mollusca: Gastropoda)". Journal of ZoologyJournal of ZoologyThe Journal of Zoology is a scientific journal concerning zoology, the study of animals. It was founded in 1830 by the Zoological Society of London and is published by Wiley-Blackwell. It carries original research papers, which are targeted towards general readers...
207(2): 201-211. doi:10.1111/j.1469-7998.1985.tb04924.x. - Durr H. J. R. (1946). "A contribution to the morphology and bionomics of Theba pisana (Muller) (Gastropoda: Helicidae)". South African Department of Agriculture. Stellenbosch-Elsenburg Science Series 47: 1-34.
- Gess S. & Gess F. (2007). "Snail Invasion: The potential impact of the invasive Mediterranean snail, Theba pisana on our coastal dune vegetation". Veld and Flora 93: 216-218.
- Hazel W. N. & Johnson M. S. (1990). "Microhabitat choice and polymorphism in the land snail Theba pisana (Müller)". HeredityHeredity (journal)Heredity is a scientific journal concerned with heredity in a biological sense, i.e. genetics. It was founded by R.A. Fisher and C. D. Darlington in 1947. It is the official journal of The Genetics Society....
65: 449-454. doi:10.1038/hdy.1990.116. - McQuaid C. D., Branch G. M. & Frost P. G. (1979). "Aestivation behaviour and thermal relations of the pulmonate Theba pisana in a semi-arid environment". Journal of Thermal Biology 4(1): 47-56. doi:10.1016/0306-4565(79)90045-7.
External links
- white garden snail on the NAPPO site
- white garden snail on the UFUniversity of FloridaThe University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
/ IFASInstitute of Food and Agricultural SciencesThe University of Florida’s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information...
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