The commonest slug in NW Europe (Kerney & Cameron 1979) and the major pest slug in agriculture, worldwide.
Native to: Europe, Mediterranean countries, and Atlantic Ids (Quick 1960). More rare and resticted to cultivated fields in the southeast, particularly in the Balkans, probably absent from Greece and Bulgarian mountains.
Introduced as a synanthrope to many regions: North America, Peru, South Africa, Tasmania, New Zealand, central Asia.
Type Locality: Frideriksdal near København, Denmark.
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) It has a wide global distribution and is found in most temperate and subtropical regions (Roth and Sadeghian, 2003) including Asia, Australia, Canada, Europe, New Zealand, the United States, South Africa, South America, and islands of the Pacific and Atlantic Oceans but its native range is thought to be western Europe (Forsyth, 2004).
External: Slug very variable, creamy or light coffee cream, rarely blackish spotted (slugs with spots may appear blackish); behind the mantle the dark spots form a reticulate pattern in the skin grooves; skin thick with large tubercles; pneumostome 2/3 back from front of mantle; pale pneumostome edge; short keel; abrupt truncation of tail tip; 3-part, pale sole; mucus colourless, on irritation milky white (calcareous granules in white mucus).
Internal: Brown ovotestis; albumen gland light brown and liver-shaped; penis fleshy and with a silky sheen, in the shape of an irregular sac, in fully mature specimens divided into 2 parts by a deep lateral constriction; penial gland of very variable shape, usually consisting of a few branches or a single long branch (1-4 knobby processes); stimulator large, conical and narrow; retractor muscle inserted laterally on penis; vas deferens opens into penis wall facing the external body side; short, straight oviduct; narrow spermatheca; small atrium; rectal caecum large.
The slug cannot be distinguished from many other Deroceras species based only on its external appearance. Similar to D. agreste and D. rodnae (Kerney & Cameron 1979); different from D. laeve and D. carunae: opaque skin, white mucus when irritated, bigger size, rectal caecum presence (Quick 1960).
Eggs: 3 x 2.5 mm, translucent, begin with calcareous speckles on surface. Up to 700 eggs are produced per individual slug (Quick 1960).
Juveniles: 4 mm long, light gray and translucent at hatching (Quick 1960).
Up to 40-60 mm long (preserved 25-30 mm); varies in size according to the habitat.
Brown, grey or creamy coloured, usually with some darker spots. Grows up to 5cm. Has a keel, or raised ridge, on rear third of body, and has the pulmonary aperture in the rear of the mantle, on the right-hand side.
At present almost exclusively restricted to cultivated areas, usually in open habitats, in meadows, near roadsides, in ruins, gardens and parks, not inside forests. Shelters under stones, fallen logs, vegetation, and ground litter (does not burrow into the soil). Can reach high abundances in cultivated land; widespread and common in invaded habitats (Chichester & Getz 1969).
Habitat Type: Terrestrial
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Species is omnivorous, feeding mainly on fresh leaves and fruits or seedings. Consumes live plants (favored more than most other gastropods), dead plants, and wood (Chichester & Getz 1973; Jennings & Barkham 1975; Herbert 2010).
larva of Tetanocera elata is endoparasitoid of Deroceras reticulatum
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: > 300
Comments: Multiple species of Deroceras spp. were recorded in eastern Maine (11 of 101 sites) from litter samples in a variety of habitats (Nekola, 2008). In New York, Hotopp and Pearce (2007) report it from 7 counties in central and southeastern regions as introduced It was documented recently in southeastern Wisconsin (Jass, 2006). In California it occurs in 24 counties: Alameda, Butte, Calaveras, Contra Costa, Del Norte, Los Angeles, Marin, San Bernardino, San Francisco, Tulare, Santa Clara, Ventura, Humboldt, Imperial, Kern, Monterey, Sacramento, San Luis Obispo, Shasta, San Mateo, Santa Barbara, Santa Cruz, Sonoma, and Riverdale (McDonnell et al., 2009). It had been documented historically in Colorado (Cockerell, 1927) as Agriolimax agrestis. Forsyth (2006) documented introduced populations at Lac des Arcs, Alberta and museum records from Waterton Lake National Park (verified anatomically). Forsyth (2005) documented it in the Upper Fraser Basin of central British Columbia at an abandoned farm site, roadside highway pullouts, and a provincial park but is widely introduced in the rest of British Columbia; including one site (along a lake shoreline near Mackenzie) in the Peace River- northern Rockies region (Forsyth, 2005). Most recently, it was discovered in the Ktunaxa Traditional Territory in southeastern British Columbia (which extends from near Canada - U.S. border north to about 50 km north of Cranbrook) (Ovaska and Sopuck, 2009).
D. reticulatum are attacked by parasites including Sciomyzid glies and nematodes. Some English populations of D. reticulatum have high rates of Sciomyzid fly infection (Stevenson & Knutson 1966, in Hunter 1978). D. reticulatum are susceptible to and experienced mortality from P. hermaphrodita (Grewal et al. 2003), which enter slugs' mantle cavities, reach adulthood, and reproduce (causing swelling of the mantle); the second generation tends to kill slug (Wilson & Grewal 2006).
In defense against predators, Deroceras reticulatum is capable of tail autotomization, followed by fleeing and hiding (Solem 1974; Pakarinen 1994a).
Life History and Behavior
Not aggressive (Rollo & Wellington 1979); aggregations occur with bad moisture and temp levels (Rollo & Wellington 1981). Homes to shelter (Cook 1979).
Life cycle covers a few months, usually two generations; main reproductive phase in summer and autumn, maximum age about a year; slugs die at the first frosts. Usually only eggs hibernate, sometimes also juveniles.
In Britain, slugs mate year round; they can reach adulthood in 3 months during summer (Quick 1960). In Michigan, only (a few) adults emerged in early spring, immediately laid eggs after emergence and through the fall, and juveniles appeared in June; here, it is an annual species (Getz 1959).
Physiology and Cell Biology
Molecular Biology and Genetics
Barcode data: Deroceras reticulatum
There are 2 barcode sequences available from BOLD and GenBank. Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species. See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Deroceras reticulatum
Public Records: 2
Specimens with Barcodes: 17
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNA - Not Applicable
Rounded National Status Rank: NNA - Not Applicable
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Reasons: It has a wide global distribution and is found in most temperate and subtropical regions (Roth and Sadeghian, 2003) including Asia, Australia, Canada, Europe, New Zealand, the United States, South Africa, South America, and islands of the Pacific and Atlantic Oceans but its native range is thought to be western Europe (Forsyth, 2004).
In North and central European lowlands, Great Britain and Ireland; probably the most widely distributed slug. Scarce and mainly as a synanthrope in N Scandinavia.
Global Short Term Trend: Relatively stable (=10% change)
Global Long Term Trend: Increase of 10-25% to decline of 30%
Degree of Threat: Low
Relevance to Humans and Ecosystems
Deroceras reticulatum is the major slug pest worldwide in agriculture (Ester & Wilson 2006), consuming seedlings and green vegetation (Quick 1960). They are known pests on oilseed rape, cabbage, brussels sprouts, ice berg lettuce, and other plants (Ester & Wilson 2006). After several years with continuous moist weather conditions, abundance can seriously increase.
Deroceras reticulatum, common names the "grey field slug" and "grey garden slug", is a species of small air-breathing land slug, a terrestrial pulmonate gastropod mollusk in the family Agriolimacidae. This species is an important agricultural pest.
Native distribution of this slug species is Europe, North Africa and the Atlantic Islands. It occurs widely in Europe, but is more rare and restricted to cultivated fields in the southeast, particularly in the Balkans, and is probably absent from Greece and the Bulgarian mountains. In the north and central European lowlands, Great Britain, and Ireland, it is probably the most widely occurring slug. In northern Scandinavia it is scarce, and is mainly found as a synanthrope.
This species occurs in countries and islands including:
- Great Britain
- Czech Republic - least concern (LC)
The species has been widely introduced as a synanthrope to many regions:
- North America, in parts of Northern Michigan and Southern Michigan
- Argentina - major slug pest in Buenos Aires province
- New Zealand
- central Asia
As all other Deroceras it has a short keel at the back of the body. Deroceras reticulatum is very variable in colour, creamy or light coffee cream, rarely blackish spotted (slugs with spots may appear blackish). Behind the mantle there is the dark spots form a reticulate pattern. The skin is thick. Mucus is colourless, on irritation milky white. The slug cannot be distinguished from many other Deroceras species based only on its external appearance.
Reproductive system: Penis is fleshy and with a silky sheen, in the shape of an irregular sac, in fully mature specimens divided into 2 parts by a deep lateral constriction. Penial gland has very variable shape, usually a few branches or a single long branch. Stimulator is large, conical and narrow. Retractor of the penis is inserted laterally. Vas deferens opens into penis wall facing the external body side. Rectal caecum is large.
This slug can travel up to 40 feet (12.2 m) in one night.
Deroceras reticulatum is almost exclusively restricted to cultivated areas, usually in open habitats, in meadows, near roadsides, in ruins, gardens and parks, not inside forests. It shelters under stones and ground litter (It does not burrow into the soil). It is active at night.
This species is omnivorous, feeding mainly on fresh leaves and fruits or seedings. Deroceras reticulatum is a serious pest of agricultural crops, garden cultivations and horticulture. After several years with continuous moist weather conditions abundance can seriously increase.
- the European garden beetle Carabus nemoralis, is a beneficial predator (from the human perspective) because it eats the young of this species and also their eggs.
- Pterostichus melanarius
- Pterostichus madidus
- Nebria brevicollis
- Scarites anthracinus eats eggs and slugs in Argentina.
- Poecilus cupreus
The bacterium Moraxella osloensis is a mutualistic symbiont of the slug-parasitic nematode Phasmarhabditis hermaphrodita. In nature, Phasmarhabditis hermaphrodita vectors Moraxella osloensis into the shell cavity of the slug host Deroceras reticulatum in which the bacteria multiply and kill the slug.
Parasites of Deroceras reticulatum include:
- Cirrus Digital: Gray Garden Slug Deroceras reticulatum
- 2006 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Cited 10 May 2007.
- Müller O. F. (1774). Vermivm terrestrium et fluviatilium, seu animalium infusoriorum, helminthicorum, et testaceorum, non marinorum, succincta historia. Volumen alterum. pp. I-XXXVI [= 1-36], 1-214, [1-10]. Havniae & Lipsiae. (Heineck & Faber).
- "Species summary for Deroceras reticulatum". AnimalBase, last modified 29 August 2010, accessed 10 December 2010.
- (Czech) Horsák M., Juřičková L., Beran L., Čejka T. & Dvořák L. (2010). "Komentovaný seznam měkkýšů zjištěných ve volné přírodě České a Slovenské republiky. [Annotated list of mollusc species recorded outdoors in the Czech and Slovak Republics]". Malacologica Bohemoslovaca, Suppl. 1: 1-37. PDF.
- Juřičková, L.; Horsák, M.; Beran, L. (2001). "Check-list of the molluscs (Mollusca) of the Czech Republic". Acta Soc. Zool. Bohem 65: 25–40.
- Balashov I. & Gural-Sverlova N. 2012. An annotated checklist of the terrestrial molluscs of Ukraine. Journal of Conchology. 41 (1): 91-109.
- Hausdorf B. (May 2002). "Introduced Land Snails and Slugs in Colombia". Journal of Molluscan Studies 68 (2): 127–131. doi:10.1093/mollus/68.2.127. PMID 12011238.
- Tulli M. C., Carmona D. M., López A. N., Manetti P. L., Vincini A. M. & Cendoya G. (2009). "Predation on the slug Deroceras reticulatum (Pulmonata: Stylommatophora) by Scarites anthracinus (Coleoptera: Carabidae)". Ecología Austral. 19: 55-61. PDF.
- "PACIFIC NORTHWEST NURSERY IPM. Snails/Slugs". Oregon State University, last modified 29 July 2005.
- Oberholzer F. & Frank T. (2003). "Predation by the carabid Beetles Pterostichus melanarius and Poecilus cupreus on Slugs and Slug Eggs". Biocontrol Science and Technology 13(1): 99-110. doi:10.1080/0958315021000054421.
- An R., SreevatsanS. & Grewal P. S. (2008). "Moraxella osloensis Gene Expression in the Slug Host Deroceras reticulatum". BMC Microbiology 8: 19. doi:10.1186/1471-2180-8-19.
- Sproston, E. L.; MacRae, M.; Ogden, I. D.; Wilson, M. J.; Strachan, N. J. C. (2006). "Slugs: Potential Novel Vectors of Escherichia coli O157". Applied and Environmental Microbiology 72 (1): 144–149. doi:10.1128/AEM.72.1.144-149.2006. PMC 1352200. PMID 16391036.
- Michigan Department of Natural Resources and Environment. "Brainworm". accessed 14 December 2010.
Names and Taxonomy
Comments: Deroceras reticulatum was until recently included under the name Agriolimax agrestis (Linnaeus, 1758) in older literature. Deroceras agreste, however, is a separate species and records of D. agreste in B.C. probably refer to D. reticulatum (Forsyth, 2004).