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Terrestrial
Gastropods of the Columbia Basin, British Columbia
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AGRIOLIMACIDAE Wagner, 1935
Genus Deroceras Rafinesque, 1820 These
small slugs can be difficult to identify and may require dissection.
There are two native and two introduced European species in British
Columbia. Deroceras laeve
(Müller, 1774): Meadow Slug Description: A small slug (extended length, to about 25 mm), amber or dark brown without spots or other markings; mantle skin with a pattern of concentric rings that is centred to the right of the midline; pneumostome behind the middle of the mantle; keel not complete and very short, only at the end of the tail; trail abruptly truncate, rather than gradually tapering to a point; mucous thin, watery and clear; sole pale brownish. Internal shell oblong, with its nucleus terminal and to the left of centre. Similar species: Deroceras reticulatum is larger than D. laeve, measuring 35-50 mm long when extended; anatomically D. reticulatum has a complex flagellum (=penial appendage) having 1-4 knobby or serrated processes (Kerney & Cameron 1979). When disturbed, D. reticulatum secretes a milky white body mucous (otherwise it is clear); the mucous of D. laeve is clear and never whitish. Habitat: Deroceras laeve favours very wet places (Kerney & Cameron 1979). In British Columbia this slug has been found living in moist habitats, in leaf litter, grass and sedges. Range: Holarctic. In North America, from the Arctic south throughout Canada and the United States and into Central America (Pilsbry 1948). Distribution: The distribution of this species in British Columbia is not well known, but it is likely throughout the province. Name: Genus name meaning "neck-horn", referring to the tentacles on the head. Species name meaning "smooth", which was probably a comparison to Arion species (some of which have coarse turbercules on the back). Records: Hwy 1, 4 km E of Canyon Hot Spring
(circa 51°09.5'N, 117°49'W) (Staatliches Museum für
Naturkunde Görlitz p5951). RBCM records (not dissected,
but presumed to be this species): Creston Valley Wildlife Management
Area (49°07.19'N, 116°37.82'W) (RBCM 998-00282-007); Bull
River near junction of Bull River and Kootenay River (49°28.35'N,
115°27.04'W) (RBCM 998-00301-001); W side of Slocan River, just
S of Winlaw (49°35.66'N, 117°35.47'W) (RBCM 998-00279-002);
N end of Slocan Lake (49°54.04'N, 117°23.25'W) (RBCM 998-00266-005).
View the map. Deroceras reticulatum
(Müller, 1774): Gray Fieldslug Description: A small slug (extended length, 35-50 mm), ground colour cream and usually with darker brown flecks; mantle skin with a pattern of concentric rings that is centred to the right of the midline; pneumostome behind the middle of the mantle; keel not complete and very short, only at the end of the tail; trail abruptly truncate, rather than gradually tapering to a point; when irritated, body mucous thick, white and sticky; sole whitish. Internal shell oblong, with its nucleus terminal and to the left of centre. Similar species: Deroceras laeve, and additional European species; see Kerney & Cameron (1979). Habitat: Gardens and other disturbed sites. Range: Europe (Kerney & Cameron 1979). Widely introduced. Distribution. Probably widely introduced into many places throughout British Columbia. Notes: Deroceras reticulatum was until recently included under the name Agriolimax agrestis (Linnaeus, 1758) in older literature. Deroceras agreste, however, is a separate species and presumably not introduced into British Columbia, although reported from British Columbia as early as the 1880s (Taylor 1892b), but records of D. agreste in B.C. probably refer to D. reticulatum. Rollo & Wellington (1975) failed to find D. agreste in the Vancouver area. Name: Species name meaning "netted". Records: Kaslo (49°55'N, 116°55'W) (Staatliches Museum für Naturkunde Görlitz p5949); Columbia Lake adjacent to Canal Flats Provincial Park (50°10.65'N, 115°49.03'W) (RBCM 998-00294-001). View the map.
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