Invasive Species Compendium

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Datasheet

Oxychilus alliarius
(garlic snail)

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Datasheet

Oxychilus alliarius (garlic snail)

Summary

  • Last modified
  • 16 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Oxychilus alliarius
  • Preferred Common Name
  • garlic snail
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Mollusca
  •       Class: Gastropoda
  •         Subclass: Pulmonata
  • Summary of Invasiveness
  • Oxychilus alliarius, commonly known as garlic snail, is a small terrestrial glass snail with a blackish-blue body and reddish to greenish shell. It is native to Western and Central Europe, mostly restricted to...

  • Principal Source
  • Draft datasheet under review

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Pictures

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PictureTitleCaptionCopyright
Oxychilus alliarius (garlic snail); live habit. Gamlingay Wood, Cambridgeshire, England.
TitleHabit
CaptionOxychilus alliarius (garlic snail); live habit. Gamlingay Wood, Cambridgeshire, England.
Copyright©Andrew Dunn/Cambridge, United Kingdom - CC BY-SA 2.0
Oxychilus alliarius (garlic snail); live habit. Gamlingay Wood, Cambridgeshire, England.
HabitOxychilus alliarius (garlic snail); live habit. Gamlingay Wood, Cambridgeshire, England.©Andrew Dunn/Cambridge, United Kingdom - CC BY-SA 2.0
Oxychilus alliarius (garlic snail); shell.
TitleShell
CaptionOxychilus alliarius (garlic snail); shell.
Copyright©Angelo Rosina-2012/via wikipedia - CC BY-SA 3.0
Oxychilus alliarius (garlic snail); shell.
ShellOxychilus alliarius (garlic snail); shell.©Angelo Rosina-2012/via wikipedia - CC BY-SA 3.0
Oxychilus alliarius (garlic snail); shell, showing umbillicus.
TitleShell
CaptionOxychilus alliarius (garlic snail); shell, showing umbillicus.
Copyright©Angelo Rosina-2012/via wikipedia - CC BY-SA 3.0
Oxychilus alliarius (garlic snail); shell, showing umbillicus.
ShellOxychilus alliarius (garlic snail); shell, showing umbillicus.©Angelo Rosina-2012/via wikipedia - CC BY-SA 3.0
Oxychilus alliarius (garlic snail); selection of empty shells. Collected from Schleswig-Holstein near Korügen-Möltenort, Germany. September 1980. Note scale.
TitleEmpty shells
CaptionOxychilus alliarius (garlic snail); selection of empty shells. Collected from Schleswig-Holstein near Korügen-Möltenort, Germany. September 1980. Note scale.
CopyrightPublic Domain - released by Francisco Welter Schultes/http://www.animalbase.uni-goettingen.de/zooweb/
Oxychilus alliarius (garlic snail); selection of empty shells. Collected from Schleswig-Holstein near Korügen-Möltenort, Germany. September 1980. Note scale.
Empty shellsOxychilus alliarius (garlic snail); selection of empty shells. Collected from Schleswig-Holstein near Korügen-Möltenort, Germany. September 1980. Note scale.Public Domain - released by Francisco Welter Schultes/http://www.animalbase.uni-goettingen.de/zooweb/

Identity

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Preferred Scientific Name

  • Oxychilus alliarius (Miller, 1822)

Preferred Common Name

  • garlic snail

Other Scientific Names

  • Helicella steenstrupii Mörch, 1857
  • Helix alliaria Miller, 1822
  • Helix alliarius Miller, 1822
  • Helix foetida Brown, 1827
  • Helix remota Benson, 1851
  • Ortizius alliarius (Miller, 1822)
  • Oxychilus tasmanicus McLauchlan, 1954
  • Polita alliaria Connolly 1912

International Common Names

  • English: garlic glass-snail
  • French: luisant aillé

Local Common Names

  • Austria: knoblauch-glanzschnecke
  • Finland: laukkakotilo
  • Germany: knoblauch-glanzschnecke
  • Netherlands: lookglansslak
  • Poland: szklarka czosnkowa
  • Sweden: löksnäcka

Summary of Invasiveness

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Oxychilus alliarius, commonly known as garlic snail, is a small terrestrial glass snail with a blackish-blue body and reddish to greenish shell. It is native to Western and Central Europe, mostly restricted to regions influenced by the Atlantic climate. The species has been introduced to northeastern North America, the pacific regions of the US and Canada as well as other temperate regions of the world. It is thought to have spread mainly via the trade of organic material. O. alliarius inhabits primarily forests, agricultural land, rocks and gardens. At the edge of its natural range in Scandinavia or southwest Poland the species occurs mainly in synanthropic habtats, often being restricted to greenhouses. A predator of small snails, it is thought to negatively impact native snail communities where introduced. According to Welter-Schultes (2013), O. alliarius is considered vulnerable in Niedersachsen and Rheinland-Pfalz (federal states of Germany).

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Mollusca
  •             Class: Gastropoda
  •                 Subclass: Pulmonata
  •                     Order: Stylommatophora
  •                         Suborder: Sigmurethra
  •                             Unknown: Gastrodontoidea
  •                                 Family: Oxychilidae
  •                                     Genus: Oxychilus
  •                                         Species: Oxychilus alliarius

Notes on Taxonomy and Nomenclature

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Oxychilus alliarius (Miller, 1822) belongs to the gastropod family Oxychilidae, the glass snails.

The specific and common name of O. alliarius, garlic snail, is derived from the fact that this snail produces a garlic odour when disturbed – garlic is an ‘allium’, hence ‘alliarius’ (Lloyd, 1970a).

Description

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As with many representatives of the family Oxychilidae, O. alliarius has a considerably smooth, shiny and opaque shell, weakly reddish to greenish brown in colour. The underside is often more whitish opaque (Kerney et al., 1983). The shell consists of 4-4.5 slightly convex whorls, with the last whorl often weakly descending near aperture. With 1/6 of the total diameter the umbilicus is wide (Welter-Schultes, 2013). The size of the shell is 3.5-4mm x 5-7 mm, the diameter usually less than 7 mm (0.9-1 mm at 1 whorl, 1.8-2.1 mm at 2 whorls, 3.4-3.6 mm at 3 whorls, 4-4.5 mm at 3.5 whorls, 5.5-6.5 mm at 4 whorls) (Welter-Schultes, 2013).

The animal itself is blackish blue, the mantle lacking usually a blackish edge. The internal ornamentation of the proximal penis consists of not more than four longitudinal pleats, which are usually straight, sometimes slightly wavy, but never laterally branched or papillate wide (Welter-Schultes, 2013).

The species has its name from a characteristic smell of garlic, which it exudes when disturbed, touched or squashed (Kerney et al., 1983; Welter-Schultes, 2013).

Distribution

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O. alliarius is native to Western and Central Europe, mostly restricted to regions influenced by Atlantic climate. Its native range stretches to Iceland in the northwest (Roth and Sadeghian, 2003), Latvia (ZipcodeZoo, 2016) and southern Finland in the northeast (Kerney et al., 1983) and along the Atlantic coast into northern Spain (Welter-Schultes, 2013) with outlying records from central Poland (Kerney et al., 1983), the Czech Republic (Horácková and Juricková, 2009) and Portugal (Cunha et al., 2010). The species has been introduced to northeastern North America (NatureServe, 2015), the pacific regions of the US and Canada (NatureServe, 2015) as well as other temperate regions of the world such as Greenland (Roth and Sadeghian, 2003), Australia (Atlas of Living Australia, 2016), New Zealand (Barker, 1999), South Africa (Herbet, 2010), Chile (Cádiz et al., 2013) and Hawaii (Cowie, 1997).

O. alliarius is cited to occur in Greece (Riedel, 1992), considerable distance outside its native range and it remains unclear whether the species is native or has established otherwise in this country. Similarly, it is not clear whether O. alliarius is native to mainland Portugal (De Oliveira and Altonaga, 2010) although an occurrence in this country fits into its overall European range. It is also mentioned to occur in China and Antarctica (ZipcodeZoo, 2016), but no records supporting this claim could be found.

With records from Del Norte, Sonoma, Sacramento, San Francisco, Alameda, San Mateo, and San Bernardino Cos detailed information about the occurrence of O. alliarius within California, USA, is provided by Roth and Sadeghian (2003). In the US state New York, Hotopp and Pearce (2007) report the species from three counties on Lake Erie as exotic.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

Sri LankaPresentIntroducedNaggs et al., 2003

Africa

RéunionPresentIntroducedStévanovitch, 1994; Griffith and Florens, 2006
Saint HelenaPresentIntroducedCrowley and Pain, 1977; Barker, 1999
-Tristan Da CunhaPresentIntroduced Invasive Preece, 2001; Jones et al., 2003Gough
South AfricaPresentIntroducedbefore 1894Barker, 1999; Herbert, 2010
Spain
-Canary IslandsPresentIntroducedKappes et al., 2009

North America

CanadaPresentPresent based on regional distribution.
-British ColumbiaPresentIntroducedForsyth, 2004; NatureServe, 2015
-Nova ScotiaPresentIntroducedWhite-McLean, 2011
-OntarioPresentIntroducedWhite-McLean, 2011
-QuebecPresentIntroducedWhite-McLean, 2011
GreenlandPresentIntroducedRoth and Sadeghian, 2003
USAPresentPresent based on regional distribution.
-CaliforniaPresentIntroducedNatureServe, 2015
-ColoradoPresentIntroducedRoth and Sadeghian, 2003; NatureServe, 2015
-HawaiiPresentIntroduced1937 Invasive Cowie, 1997; Howarth et al., 2003; NatureServe, 2015Hawaii, Kauai, Molokai, Maui
-IdahoPresentIntroducedNatureServe, 2015
-MichiganPresentIntroducedNatureServe, 2015
-MontanaPresentIntroducedNatureServe, 2015
-New JerseyPresentIntroducedNatureServe, 2015
-New YorkPresentIntroducedNatureServe, 2015
-North CarolinaPresentNativeNatureServe, 2015
-PennsylvaniaPresentIntroducedNatureServe, 2015
-WashingtonPresentIntroducedNatureServe, 2015

South America

ChilePresentIntroducedbefore 1922Odhner, 1922; Stuardo and Vega, 1985; Cádiz et al., 2013Juan Fernández Islands
ColombiaPresentIntroducedHausdorf, 2002

Europe

AustriaPresentNativeWelter-Schultes, 2013Vorarlberg
BelgiumPresentNativeKerney et al., 1983; GBIF, 2016
Czech RepublicPresentNativeHoráčková and Juřičková, 2009
DenmarkPresentNativeKerney et al., 1983
FinlandPresentNativeKerney et al., 1983
FrancePresentNativeKerney et al., 1983; GBIF, 2016
GermanyPresentNativeKerney et al., 1983; GBIF, 2016
IcelandPresentNativeRoth and Sadeghian, 2003
IrelandPresentNativeKerney et al., 1983
ItalyPresentNativeWelter-Schultes, 2013Toscana
LatviaPresentNativeZipcodeZoo, 2016
LuxembourgPresentNativeKerney et al., 1983
NetherlandsPresentNativeKerney et al., 1983; GBIF, 2016
NorwayPresentNativeKerney et al., 1983; Encyclopedia of Life, 2016Lofoten
PolandPresentNativeKerney et al., 1983
PortugalPresentCunha et al., 2010; De and Oliveira Altonaga, 2010Faial Island, Sao Miguel Island
-AzoresPresentNativeWelter-Schultes, 2013
-MadeiraPresentIntroducedSeddon, 2008; Cunha et al., 2010
SpainPresentNativeWelter-Schultes, 2013Cataluña
SwedenPresentNativeGBIF, 2016
SwitzerlandPresentNativeTurner et al., 1998; GBIF, 2016
UKPresentNativeKerney et al., 1983; GBIF, 2016Scotland, England, Ireland

Oceania

AustraliaPresentPresent based on regional distribution.
-New South WalesPresentAtlas of Living Australia, 2016
-QueenslandAtlas of Living Australia, 2016
-South AustraliaPresentAtlas of Living Australia, 2016
-TasmaniaPresentIntroducedKershaw, 1991; Atlas of Living Australia, 2016
-VictoriaPresentAtlas of Living Australia, 2016
-Western AustraliaPresentAtlas of Living Australia, 2016
New ZealandPresentIntroducedBarker, 1999

History of Introduction and Spread

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Musson (1891) recorded Zonites nitidus Müller, 1774 (= Zonitoides nitidus) from Australia and New Zealand. However, the presence of this species in New Zealand could not be confirmed and the New Zealand records of Musson should be referred to O. alliarius (Barker, 1999). This was subsequently done by Taylor (1906) who added additional records for this species for New Zealand. It is likely that that O. alliarius was well established in the North Island by the early twentieth century (Barker, 1990). Both O. alliarius and Z. nitidus occur in Australia, and Musson's records of Z. nitidus from that country are likely to include both species (Barker, 1999).

In South Africa O. alliarius has so far been recorded from five provinces (Herbert, 2010). Here it was present before 1894 with an early record from Grahamstown, Eastern Cape dating from 1912 (Connolly, 1912; 1916).

O. alliarius was first recorded from Chile in 1922 (Odhner, 1922).

Risk of Introduction

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O. alliarius has been found in shipments of ornamental plants from Europe to the USA (USDA, 1964) (see Movement and Dispersal section). This indicates that risks of accidental introduction are highest when phytosanitary standards fail to intercept snails from shipments within the horticultural trade. There are no indications that the species has been deliberately introduced to new areas in the past.

Habitat

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In its native range, O. alliarius is a fairly widespread generalist living in sheltered locations within a wide range of habitats. It occurs under logs and stones, amongst hedge banks, beneath ground-cover plants and in leaf litter (Killeen, 1992). Main habitats include forests, including acidic ones such as conifer plantations, but also fields, gardens and greenhouses (Kerney et al., 1983). It is often found in swampy habitats of mountain slope forests under moss and also in humid and shady rocky habitats in creek gorges, swampy meadows, at water margins and in cultivated areas with moist meadows (Welter-Schultes, 2013).

Most South African records are from synanthropic habitats such as gardens and disturbed land, but the species has also been found in indigenous forest in the Pietermaritzburg area (Herbert, 2010).

O. alliarius was found to be the most abundant mollusc recorded in the ‘Hakalau Forest National Wildlife Refuge’, on the windward slopes of Mauna Kea, Hawaii, USA (Howarth et al., 2003). Here, this species was found in large numbers in the leaf litter, on mossy rocks, fallen bark of trees, and under rocks (Howarth et al., 2003).

In New Zealand, O. alliarius occurs in a variety of modified habitats, including greenhouses, gardens, roadsides, hedgerows, parks, plantations, and pastures (Suter, 1913; Barker, 1999). On the North Island the species is abundant in modified environments, including improved pastures, but on the South Island it seems to be restricted to urban areas (Barker, 2002).

Habitat List

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CategoryHabitatPresenceStatus
Terrestrial-managed
Cultivated / agricultural land Present, no further details Natural
Disturbed areas Present, no further details Natural
Managed forests, plantations and orchards Principal habitat Natural
Managed grasslands (grazing systems) Present, no further details Natural
Protected agriculture (e.g. glasshouse production) Present, no further details Natural
Rail / roadsides Present, no further details Natural
Urban / peri-urban areas Present, no further details Natural
Terrestrial-natural/semi-natural
Natural forests Principal habitat Harmful (pest or invasive)
Natural forests Principal habitat Natural
Natural grasslands Principal habitat Natural
Rocky areas / lava flows Principal habitat Natural
Scrub / shrublands Present, no further details Natural

Hosts/Species Affected

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O. alliarius, a facultative carnivorous species, has not been reported as a major pest of specific crops. However, the species is primarily vegetarian, and frequently attains pest status in greenhouses on tender plants such as ferns (Barker, 1999).

Biology and Ecology

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Reproductive Biology

The eggs of O. alliarius are about 1 mm in diameter and white, owing to a calcareous shell (Barker, 1999).

Physiology and Phenology

When disturbed, O. alliarius produces a garlic odour from a cluster of gland cells close to the pneumostome at the right side of the mantle. Here, cells are rich in proteinaceous material which contains sulphur compounds (Lloyd 1970a). The main component of the volatile odour is n-propyl mercaptan (i-propanethiol) (Lloyd, 1970b, c). The garlic odour exuded when threatened seems to be effective in deterring predators, such as hedgehogs, from feeding on this species. When equal numbers of four species of Oxychilus were presented to hedgehogs (Erinaceus europaeus), fewer O. alliarius were eaten compared to the other species (Barker, 1999; Allen, 2004).

Population Size and Structure

O. alliarius can be a dominant snail species in some habitats throughout its native range (e.g., 13 to 20 specimens per m2 in England (Mason, 1970a) and 22 specimens per m2 in the Canary Islands (Kappes et al., 2009).

O. alliarius is considered to be a gregarious species but no further details are available (Barker, 1999; White-McLean, 2016).

Nutrition

O. alliarius consumes living and dead plant material as well as small snails and their eggs (Mason, 1970b; Barker, 1999; Welter-Schultes, 2013;  White-McLean, 2011). Taylor (1902) records the snails Physa fontinalis and Succinea putris as prey of captive O. alliarius, both species being widespread throughout the native range of this species.

O. alliarius is a generalist snail predator feeding preferentially on the smallest snails, although the species rarely eats slugs (Meyer and Cowie, 2010). However, Oxychilus species have been recorded to predate on slug eggs (von Proschwitz, 1994). Size preference experiments indicated that O. alliarius will only consume prey less than 3 mm in shell length (Meyer and Cowie, 2010). In addition to predation on juvenile or small adult snails, members of the genus Oxychilus will radulate a small round hole in the eggshell of various gastropods to access the embryonic tissues (Barker and Efford, 2004). Cannibalism has also been reported for this species (Baur, 1992).

On Hawaii, live specimens of O. alliarius were found eating fallen 'banana poka' (Passiflora mollissima) fruits on the ground (Howarth et al., 2003).

Environmental requirements

In Switzerland, O. alliarius has been recorded up to 1,300 m altitude (Welter-Schultes, 2013).

On Hawaii, O. alliarius can be abundant in forests in excess of 2,000 m altitude (Gagné and Christensen, 1985).

O. alliarius can tolerate weakly acidic soil (Kerney et al., 1983).

Climate

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ClimateStatusDescriptionRemark
C - Temperate/Mesothermal climate Preferred Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C
Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Preferred Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Angiostrongylus cantonensis Parasite Adult Female/Adult Male not specific
Lampyridae Predator Adult Female/Adult Male not specific

Notes on Natural Enemies

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Land snails have many natural predators, including mammals (e.g. hedgehogs or mice) and birds, thrushes in particular, also slow worms and toads. Invertebrate predators include other predatory snails, ground beetles, rove beetles, centipedes, leeches, and flatworms. Also harvestmen of the family Ischyropsalidae are known to be specialised snail predators. However, there a few records of natural enemies referring directly to Oxychilus or more specifically to O. alliarius.

A number of parasitic nematodes have been recorded from Oxychilus (Barus and Blaek, 1971; Korol and Spiridonov, 1991; Roots, 1992; Baird, et al., 1994; Wilson et al., 2000), but only the rat lung worm Angiostrongylus cantonensis specifically from O. alliarius. (Kim et al., 2014).

Parasitic Diptera, particularly of the family Sciomyzidae are frequently specialised to develop in gastropods. In Britain members of this family belonging to the genus Pherbellia (e.g. Pherbellia argyra) have been recorded to parasitise Oxychilus (Smith, 1989; Foote et al., 1999).

The mite Riccardoella limacum has been recorded to parasitise on various species of Oxychilus (Badie and Rondelaud, 1985).

In captivity, O. alliarius is preyed upon by larvae of glow worms belonging to the beetle family Lampyridae (Tyler, 2015).

Means of Movement and Dispersal

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Accidental Introduction

It is likely that the most common pathway of further spread of this species will be through shipments of ornamental plants and horticultural produce. Another possibility is the spread through shipments of tiles (Herbert, 2010). Whereas adult snails can readily be detected through standard phytosanitary inspection methods, small juvenile stages and eggs are much more difficult to detect.

During the 1960s the species has been intercepted in New York, USA, from orchid shipments originating from Belgium and with rhododendron shipments originating from Ireland. In Massachusetts and Texas, O. alliarius was recorded from Hydrangea and orchid shipments originating from Italy and Mexico (USDA, 1964).

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Horticulture Yes USDA, 1964

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Plants or parts of plants Yes USDA, 1964

Environmental Impact

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Impact on Biodiversity

O. alliarius can be a dominant snail species in some habitats throughout its native range e.g. 13 to 20 specimens per m2 in England (Mason, 1970a) and 22 specimens per m2 in the Canary Islands (Kappes et al., 2009).

On Hawaii, USA, O. alliarius is believed to prey on and thus represent a threat to endemic ground-dwelling native snails, and the species has been implicated in the decline of Pacific island land snails (Severns, 1984; Barker and Efford, 2004; Meyer, 2005, 2006; Meyer and Cowie, 2010). O. alliarius preferentially feeds on the smallest snails and because many extant Hawaiian and Pacific island snail species are small, these are specifically at risk. In addition, O. alliarius rarely feeds on slugs and while co-occurring with introduced invasive slugs on Hawaii, these may not be impacted by this species (Meyer and Cowie, 2010). As a predator of smaller achatinellid (Achatinellidae) snails O. alliarius, may be in particular a potential threat to Newcombia cumingi, the Newcomb’s tree snail. N. cumingi is a member of the endemic Hawaiian subfamily Achatinellinae, which is known only from the island of Maui (Cowie et al., 1995). Currently, there is only one population of N. cumingi known to be left on this island (US Fish and Wildlife Service, 2012).

Also on Hawaii, O. alliarius may also pose a direct threat to the endangered endemic plant Schiedea membranacea, which occurs only on the island of Kauai (US Fish and Wildlife Service, 2008). Various species of introduced snails have been observed feeding on flowers and developing seed capsules, and O. alliarius is common near the remaining individuals. It seems very likely that feeding by snails is responsible for a lack of seedlings (US Fish and Wildlife Service, 1998).

O. alliarius has established in many areas of New Zealand (Barker, 1999). Amongst other species of the genus, it has been identified as a contributing agent to the decline of richness in native gastropod communities (Barker and Efford, 2004). In particular, predation by Oxychilus species on Charopidae and Punctidae endemic to New Zealand in forest habitats has been observed (Barker and Efford, 2004).

Similarly, based on its predatory feeding habit, O. alliarius is seen as a threat to native snail diversity in Australia (Atlas Living Australia, 2016), and Chile (Cadiz et al., 2013). Continental Chile has the highest generic and specific endemism known for Punctoidea in the American continent, most of them potential prey for O. alliarius (Cádiz et al., 2013; Araya, 2015).

O. alliarius has also invaded areas of native vegetation in Tristan da Cunha (Gough Island) (Preece, 2001). Aside from the fact that it has become an important prey for the invasive House mouse (Mus musculus), details of its potential impact are not known (Jones et al., 2003).

Environmental Services

As a comparably abundant species in its native range, O. alliarius may play a significant role in leaf litter decomposition (Mason, 1970a). This is mirrored by the same function in parts of its introduced range. For example, the species has been found to impact on the rate of litter decomposition in Hawaiian rainforests. This may to a certain degree mitigate the loss (potentially partly caused by this species itself) of native snail species (Meyer et al., 2013).

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Newcombia cumingi (Newcomb's tree snail)EN (IUCN red list: Endangered) EN (IUCN red list: Endangered); USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiPredationUS Fish and Wildlife Service, 2012
Schiedea membranaceaCR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered); NatureServe NatureServe; USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiHerbivory/grazing/browsingUS Fish and Wildlife Service, 1996

Social Impact

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On Hawaii, USA, O. alliarius has been recorded as host for the parasitic nematode Angiostrongylus cantoniensis, which is the cause of eosinophilic meningitis, an emerging infectious disease (Kim et al., 2014).

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Is a habitat generalist
  • Tolerant of shade
  • Capable of securing and ingesting a wide range of food
  • Benefits from human association (i.e. it is a human commensal)
  • Gregarious
  • Reproduces asexually
Impact outcomes
  • Reduced native biodiversity
  • Threat to/ loss of endangered species
  • Threat to/ loss of native species
Impact mechanisms
  • Herbivory/grazing/browsing
  • Predation
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Difficult to identify/detect as a commodity contaminant
  • Difficult to identify/detect in the field

Similarities to Other Species/Conditions

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Most likely to be confused with closely related species of the genus Oxychilus, O. alliarius differs from O. helveticus by having a wider umbilicus and a mantle edge which is not black. O. helveticus can also smell of garlic but weaker than O. alliarius (Kerney et al., 1983).=

With O. alliarius whorls, whorl three onwards are more narrowly coiled than in O. cellarius, and the last whorl is descending lower with O. alliarius compared to O. cellarius (Welter-Schultes, 2013).

O. draparnaudi is usually larger at the adult stage compared to O. alliarius and has a wider umbilicus as well as a wider last whorl (Kerney et al., 1983).

Prevention and Control

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Control

No specific measures for the control of O. alliarius have been described.

Biological control

No biological control agents have been assessed or used for the control of O. alliarius. However, larvae of the flies belonging to the family of Sciomyzidae parasitise inside aquatic and terrestrial snails and slugs, which could turn individual species into potentially suitable control agents. This has been in particular discussed in the context of a possible control of schistosomiasis and other snail-borne diseases in Africa, South America and the Far East (Smith, 1989).

Oxychilus species are themselves known to exert some control on other snail species. O. draparnaudi, a comparably large species, is an effective biological control agent of pestiferous, medium-sized O. cellarius in greenhouses. In the confined space of the greenhouse, O. draparnaudi was observed to eliminate populations of its congeneric (Barker and Efford, 2004). It is not known if O. draparnaudi would equally have some controlling impact on the comparable small-sized O. alliarius. In situations where O. alliarius has turned into an environmentally problematic species the use of a similar unspecific predator for its control would not be advisable anyway.

Gaps in Knowledge/Research Needs

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Surveys for invertebrate control agents specific to O. alliarius or the genus Oxychilus could potentially lead towards a successful biological control of this species in its introduced range.

References

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Allen JA, 2004. Avian and mammalian predators of terrestrial gastropods. In: Natural enemies of terrestrial molluscs [ed. by Barker GM]. Wallingford, UK: CABI Publishing, 1-36. http://www.cabi.org/CABeBooks/default.aspx?site=107&page=45&LoadModule=PDFHier&BookID=209

Araya JF, 2015. Current status of the non-indigenous molluscs in Chile, with the first record of Otala punctata (Müller, 1774) (Gastropoda: Helicidae) in the country and new records for Cornu aspersum (Müller, 1774) and Deroceras laeve (Müller, 1774). Journal of Natural History, 49(29/30):1731-1761. http://www.tandfonline.com/loi/tnah20

Atlas of Living Australia, 2016. Atlas of Living Australia. http://www.ala.org.au

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Links to Websites

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WebsiteURLComment
AnimalBase Project Group, 2005-2016. AnimalBase. Early zoological literature onlinehttp://www.animalbase.uni-goettingen.de/zooweb/servlet/AnimalBase/search
Encyclopedia of Lifehttp://eol.org/
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gatewayhttps://doi.org/10.5061/dryad.m93f6Data source for updated system data added to species habitat list.
Terrestrial Mollusc Toolhttp://www.idtools.org/id/mollusc

Principal Source

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Draft datasheet under review

Contributors

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29/01/2016 Original text by:

Norbert Maczey, CABI, UK

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