Deroceras (Deroceras) laeve (Müller, 1774)
meadow slug, marsh slug, smooth slug, brown slug
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).
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).
D. laeve may be able to tolerate freezing, and is active from 0-30 C (Rollo & Shibata 1991). Possible adaptations allowing it to withstand freezing are "ice nucleating agents" that control the formation of ice in its body (Cook 2004) and the production of lots of glucose (a possible cryoprotectant) with exposure to freezing (Storey et al. 2007).
D. laeve is the only land snail that goes deliberately into the water and can survive for days submerged. Can be dispersed by water currents. Eggs also survive submerged; juveniles can hatch under water and then get to the surface.
Up to 22 mm long and slightly larger, but mature specimens can be much smaller (Wiktor 2000).
Ecology and Distribution
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).
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).
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 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).
Feeds on live and dead plants, with some carrion and live invertebrates (Herbert 2010). A fairly wide range of plants is consumed (Getz 1959).
Deroceras laeve can be a serious pest in greenhouses. On the other hand, the species is threatened by continuous destructions of wet habitats by drainage, construction projects and road construction. The species has shown little evidence for significant decline in Britain. Lower concern in Switzerland.
- Limax laevis Müller, 1774 (synonym)
- Limax brunnaeus Draparnaud, 1801 (synonym)
- Limax gracilis Rafinesque, 1820 (synonym)
- Limax campestris Binney, 1841 (synonym)
- Limax parvulus Normand, 1852 (synonym)
- Limax semitectus Möch, 1857 (synonym)
- Limax weinlandii Heynemann, 1862 (synonym)
- Limax araneus Gassies, 1867 (synonym)
- Krynickillus (Malino) brunneus Mabille, 1868 (synonym)
- Krynichia americana tata, 1870 (synonym)
- Limax guatemalensis Crosse & Fischer, 1870 (synonym)
- Limax ingersolli Binney, 1875 (synonym)
- Limax montanus Ingersoll, 1875 (synonym)
- Limax hyperboreus Westerlund, 1876 (synonym)
- Limax stenuras Strebel & Pfeffer, 1880 (synonym)
- Limax jalapensis Strebel & Pfeffer, 1880 (synonym)
- Limax berendti Strebel & Pfeffer, 1880 (synonym)
- Limax hemphili Binney, 1890 (synonym)
- Agriolimax globosus Collinge, 1896 (synonym)
- Agriolimax perkinsi Collinge, 1896 (synonym)
- Agriolimax bovenoti Collinge, 1897 (synonym)
- Agriolimax berendti var. pictus Cockerell, 1897 (synonym)
- Limax (Hyrolimax) laevis Müller. Von Martens, 1898 (synonym)
- Agriolimax pseudodioicus Velitchkovsky, 1910 (synonym)
- Agriolimax motaguensis Cockerell, 1914 (synonym)
- Agriolimax renschi Wagner, 1934 (synonym)
- Agriolimax schulzi Cvetkov, 1940 (synonym)
- Deroceras monentolophus Pilsrby, 1944 (synonym)
- Deroceras schulzi Tzvetkov & Matyokin, 1946 (synonym)
- Agriolimax pellucidus Chen & Gao, 1979 (synonym)