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Marsh Slug

Deroceras laeve

Description 2

The slug is from brown to dark brown, usually with dark and characteristic but not well visible spots arranged in groups. The shape is almost cylindrical, posterior end is abruptly widened. The mantle covers 50% of body length (unusually large). There are wrinkles on skin present (may disappear in preserved slugs). Mucus is thin, colourless.

This slug is 15–25 mm long when preserved.

The populations of this species that occur in Central Europe are much darker than other Deroceras species in that area.

Reproductive system: Penis is often reduced, elongated if present, without proper penial gland but with two or more tiny glandular papillae and its end. Retractor is unforked and attached at half penis length, stimulator small, cone-shaped but looks more like a papilla. Tubular oviductus and atrium are unusually long. There is no rectal caecum.

Habitat 3

High ecological tolerance, but needs permanently wet habitats. Usually in lowlands and very humid habitats, swamps, riversides, wetlands, especially alder and oak woods, marshlands and degraded areas, also greenhouses, often near water under wood or detritus. Tolerates subpolar and tropical temperatures. Newly created habitats are often colonized after a few years. In Switzerland in up to 1800 m altitude, but usually below 1000 m, in Bulgaria in up to 2500 m.

Life cycle 4

Life cycle extremely short, down to less than a month, up to 5 generations in a year; several generations can live at the same time. Frequently there are forms with reduced penis, which reproduce by self-fertilisation. Maximum age not more than 1 year.

Can reproduce throughout the year if conditions are good (Jordaens et al. 2006). In Ontario, active April-Nov. with all life stages overwintering (Rollo & Shibata 1991); in Michigan, adults are present in spring and summer, lay eggs immediately after emergence and through the fall (Getz 1959).

Morphology 5

External: Light to dark brown, often with some small dark flecks; thin, translucent skin; mantle large, about half of body length and lighter in color; clear mucus on body and sole; slightly paler around pneumostome; short keel; sole light brown; mucus clear and watery (Quick 1960; Kerney & Cameron 1979; Wiktor 2000; Wiktor et al. 2000).

Internal: Dark ovotestis; often aphallic or otherwise with reduced penis (i.e. functionally female); if present, penis long and twisted; stimulator small, cone-shaped but looks more like a papilla; without proper penial gland but with two or more tiny glandular papillae at its end; vas deferens at 2/3 along penis's length and penial retractor at 1/2 length; two pilasters in penial flagellum; retractor unforked and attached at half penis length; tubular oviduct and atrium are unusually long; no rectal caecum (Quick 1960; Kerney & Cameron 1979; Wiktor et al. 2000).

Similar in appearance to D. sturanyi and D. caruanae (Kerney & Cameron 1979). Differs from D. reticulatum: its neck protrudes further from mantle; differs from other Deroceras species: has a "more sinuous penis" with a cylindrical appendix and is frequently aphallic (Quick 1960).

Eggs: 1.8 x 1.5 to 2 x 1.3 mm; translucent, with calcareous particles (Quick 1960).

Juveniles: 4 mm long, white, translucent at hatching with pink-brown tentacles (Quick 1960).

Behaviour 6

A fast, active crawler (Quick 1960). D. laeve can be aggressive, wounding other slugs when in high-density populations (Rollo & Wellington 1979).

Not very responsive to moisture levels. Has a wide temperature tolerance, including survival of freezing (Getz 1959).

Distribution 7

Native to the Holarctic (most of the northern hemisphere).

Today introduced worldwide except Antarctica, also on tropical islands such as New Guinea or on Pacific islands (Wiktor 2000).

Type Locality: Frideriksdal near Copenhagen, Denmark (Wiktor 2001).

Size 8

Limax laevis – “Long. 5 lin, lat. 1 lin.” (Müller, 1774)

Habitat 9

Habitat Type: Terrestrial

Comments: This species can be found in many terrestrial habitats.

Number of occurrences 10

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: > 300

Comments: This species was first recorded in Hawaii in 1897 (Cowie, 1997) but has probably become established on all main Hawaiian Islands, inclduing Lanai, Kauai, Oahu, and Maui. Recently it was found in a survey of the Hakalau region, dry gulch near University of Hawaii Hakalau Forest Biological Field Station, Hakalua Forest National Wildlife Refuge, on the windward slopes of Mauna Kea, elevation 6335-6410 feet, Hawaii, Hawaiian Islands (Howarth et al., 2003). Roth and Lindberg (1981) documented it on Attu (Aleutian Islands), Alaska. In California it is known from 14 counties: Alameda, Lake, Los Angeles (including Santa Catalina Island), Marin, Nevada, Placer, Shasta, San Bernardino, San Diego, San Francisco, San Mateo, Santa Barbara (including Santa Cruz Island), Santa Cruz (Roth and Sadeghian, 2006), and Humboldt (McDonnell et al., 2009). It had been documented historically in Colorado (Cockerell, 1927) as Agriolimax campestris. 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 four counties that are widespread, though it is likely poorly represented. It has been documented recently in southeastern Wisconsin (Jass, 2006). This species is also known from Pleistocene deposits in the Black Hills of Fall River/Custer Cos., South Dakota (Jass et al., 2002). Freeman and Perkins (1992) documented it in Nebraska along the entire Platte River valley. Branson (1966) includes a single site on the Spring River in Missouri. Baxter (1987) cites occurrences in Alaska across much of the state. In Alberta, it is distributed south west of Calgary, north to Lake Louise and Jasper, east to Edmonton and north to Slave Lake (Lepitzki, 2001). It was recently documented in 2 of 82 soil samples and 6 area spot searches of Wind Cave National Park, South Dakota, in 2002 (Anderson, 2005). Pearce (1994) reported it from Mackinac Island, Michigan. Forsyth (2005) documented it in the Upper Fraser Basin of central British Columbia along the shorelines of waterways and permanently wet forested sites; as well as in the Peace-River- northern Rockies region in a small pond west of Ed Bird Lake in the Finlay River valley and in spruce and mixedwood forests such as those on the Liard Plain (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).

Ecology 11

Spring run-off probably serves to disperse D. laeve, which inhabits marshy places (Rollo & Shibata 1991).

Sciomyzid flies Tetanocera plebeia, T. valida prey on D. laeve (Foote 1963, in Stephenson & Knutson 1966). D. laeve is also susceptible to infection from the nematode Phasmarhabditis hermaphrodita (Grewal et al. 2003).

Sources and Credits

  1. (c) Paul Morris, some rights reserved (CC BY-SA), https://www.flickr.com/photos/aa3sd/3060428220/
  2. (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Deroceras_laeve
  3. (c) www.animalbase.org (F. Welter Schultes), some rights reserved (CC BY-NC), http://eol.org/data_objects/13238705
  4. (c) www.animalbase.org (F. Welter Schultes); Paustian, Megan, some rights reserved (CC BY-NC), http://eol.org/data_objects/13238706
  5. (c) Paustian, Megan; www.animalbase.org (F. Welter Schultes), some rights reserved (CC BY-NC), http://eol.org/data_objects/17764869
  6. (c) Paustian, Megan, some rights reserved (CC BY-NC), http://eol.org/data_objects/17764868
  7. (c) www.animalbase.org (F. Welter Schultes); Paustian, Megan, some rights reserved (CC BY-NC), http://eol.org/data_objects/17764871
  8. (c) see citation for reference, some rights reserved (CC BY-NC), http://eol.org/data_objects/17564465
  9. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28873030
  10. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28873023
  11. (c) Paustian, Megan, some rights reserved (CC BY-NC), http://eol.org/data_objects/13238704

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