First records of the European land slug Lehmannia valentiana in British Columbia, Canada
Abstract: The synanthropic slug, Lehmannia valentiana (Férussac, 1821), is recorded in British Columbia for the first time. The identification of an adult specimen from Victoria, Vancouver Island, is confirmed by dissection. Additional records, based on undissected immature specimens, photographs and sightings, are known from nearby sites on southern Vancouver Island and from an island in the Strait of Georgia.
Some European terrestrial slugs have shown great ability for dispersal by human beings and colonize new areas throughout the world. Since the discovery of the first introduced species of slug in British Columbia by Taylor (1889, 1891), many additional species have been encountered. Presently there are at least 13 introduced species confirmed for the province, including Lehmannia valentiana (Férussac in Férussac & Deshayes, 1821) (Figure 1). The exact number of species is complicated by unconfirmed accounts and problems with species recognition in the genus Arion. Carl and Guiguet (1958, 1972) and Hanna (1966) summarized what was known for the exotic slug species in British Columbia before the mid-1970s. Rollo and Wellington (1975) presented updated and new information on European slugs in Greater Vancouver and the lower Fraser Valley. Most recently, Reise et al. (2000) detailed the first records of Boettgerilla pallens Simroth, 1912, in British Columbia and North America. Nevertheless, the extent of invasion by exotic slugs in British Columbia remains incompletely known.
Figure 1. Lehmannia valentiana from Victoria, British Columbia (RBCM 000-00147-001). Figure 2. Distal genitalia of a Victoria, British Columbia specimen of Lehmannia valentiana (RBCM 000-072-002); fl = penial flagellum; ov = oviduct; P = penis; r = penial retractor;
sp = spermatheca; vd = vas deferens.
A number of slug species have enlarged their range and become more abundant worldwide due to habitat modification by humans. Reduced species diversity brought on by agricultural and horticultural activities allow for synanthropic slug species to flourish. In turn, slugs are agricultural and horticultural pests, capable of much damage to crops (South, 1992; Waldén, 1960). Exotic slugs can also act as vectors of plant diseases and animal parasites, or compete with native species (South 1992; Rollo & Wellington, 1979; Rollo, 1983a, b).
Lehmannia valentiana, native to the Iberian Peninsula, is now widely introduced in Europe and worldwide (Waldén, 1961; Kerney & Cameron, 1979; South, 1992). In North America, Lehmannia valentiana has also been reported as L. poirieri (Mabille, 1883) and L. marginata (or Limax marginatus). L. poirieri is a synonym of L. valentiana (Waldén, 1960, 1961), and most North North American records of L. marginatus were based on L. valentiana (Quick, 1960).
In Britain L. valentiana was known only from greenhouses until recently when it was discovered at open sites (Kerney, 1987). In North America it has been found in greenhouses and at cultivated or otherwise disturbed open sites (Getz & Chichester, 1971). L. valentiana is well established in California (Hanna, 1966, as Limax marginatus), but in Canada it is previously only known to be introduced into Winnepeg, Manitoba, where the species is confined to greenhouses and is incapable of overwintering in the open (Howe & Findlay, 1972). Among an assemblage of exotic slugs and snails in Lynnwood, Washington, Roth and Pearce (1984) did not find L. valentiana.
Introduction of L. valentiana into new areas is attributed to movement of plant material (Waldén, 1960; Howe & Findlay, 1972). Whereas L. marginata is arboreal, climbing trees and plants, L. valentiana is confined to the ground (Quick, 1960; Kerney & Cameron, 1979).
I report the first British Columbia records of Lehmannia valentiana. All are from open sites in the vicinity of Victoria.
Records of Lehmannia in British Columbia
Specimens of Lehmannia sp. were collected or observed at a several sites on southern Vancouver Island and the Gulf Islands, British Columbia. Specimens of Lehmannia are deposited in the Invertebrate Collection of the Royal British Columbia Museum (RBCM), Victoria. The map datum used for geopositions is NAD83.
- Vancouver Island: Victoria: 2574 Graham Street (48°26.24'N, 123°21.33 'W). RGF coll., 31 January 2000 (3 specimens, RBCM 000-00072-002), in compost bin. Ibid. RGF coll., 8 July 2000 (2 specimens, RBCM 000-00147-001), in compost.
- Vancouver Island: Colwood: E of the mouth of Colwood Creek, Esquimalt Lagoon, Royal Roads
University, (48°25.95'N, 123°28.02'W); RGF and K. Ovaska, observers, 29 July 2000 (1 individual, not collected), coniferous wooded area. - Vancouver Island: Saanich Peninsula: Central Saanich District Municipality: 2385 Twin View Drive (48°33.42'N, 123°24.75'W); K. Sendall, observor, 16 October 2000 (1 individual, not collected), in compost. Ibid. K. Sendall, collector, 28 October 2000 (2 individuals, RBCM 000-00149-001) in compost.
- Gulf Islands: North Pender Island: shopping centre, Bedwell Harbour Road (48°46.78'N, 123°16.86'W); T.J. Forsyth and RGF, collectors, 6 June 1999 (2 specimens, RBCM 999-00147-004), in garden.
The Victoria site is an urban back yard, which also has an assortment of other exotic mollusks, including: Arion hortensis aggregate; Arion subfuscus (Draparnaud, 1805); D. panormitanum (Lessona & Pollonera, 1882); Deroceras reticulatum (Müller, 1774); Limax maximus Linnaeus, 1758; and Oxychilus draparnaudi (Beck, 1837).
The North Pender Island site has Lehmannia valentiana apparently confined to a narrow garden in a shopping complex. Ornamental shrubs and small trees are planted along the north wall of a grocery store. The garden is kept moist by its northern exposure and by a trickle of water from a pipe (presumably part of the air-conditioning system). The ground is covered with layers of plastic and bark mulch. Four species of mollusks were found in association with Lehmannia: Arion subfuscus; Deroceras reticulatum; Oxychilus alliarius (J.S. Miller, 1822); and Vitrea contracta (Westerlund, 1871).
The Esquimalt Lagoon site is a remnant natural forest with invasive plant species. The dominant trees are Douglas-fir (Pseudotsuga menziesii menziesii) and Western Redcedar (Thuja plicata). Western Yew (Taxus brevifolia) and willow (Salix sp.) were also present in the immediate area where Lehmannia was observed. Herbaceous plants included native Dull Oregon-grape (Mahonia nervosa) and naturalized Spurge-laurel (Daphne laureola). Lehmannia was observed on a piece of dead wood on the ground. Other species found in the immediate area were: Ariolimax columbianus (Gould, 1851); Arion ater aggregate; Arion intermedius Normand, 1852; Haplotrerna vancouverense (Lea, 1839); Lauria cylindracea (da Costa, 1778); Monadenia fidelis (Gray, 1834); Oxychilus alliarius; Punctum randolphii Dall, 1895; and Vespericola columbianus (Lea, 1838).
In the absence of adult material from the North Pender Island and Esquimalt Lagoon sites, identification could not be verified by dissection. Identification of the Central Saanich individuals was based on photographs and external characters of subsequently collected material. All individuals, however, have the general appearance — body pigmentation, habits, etc. — of L. valentiana.
Similar species and identification
Lehmannia valentiana is a medium-sized slug (extended length up to approximately 70 mm) (Figure 1). The body is yellowish grey or yellowish violet, slightly darker on the head, and somewhat translucent. The mantle of Lehmannia bears a pattern of fine, close concentric ridges. Pigmentation of the mantle typically consists of a median dark band and a pair of dark lateral bands that form a lyre-shape. There usually is one dark band on each side of the tail and sometimes a second, weaker pair below. Young individuals tend to have darker markings, but the bands of adults are often paler and less conspicuous. The midline of the body has a ridge or keel on its posterior portion and not quite reaching the mantle. The sole is pale grey. The mucus is watery, not very sticky and colourless.
Genera that may be confused with Lehmannia include Limax and Deroceras because the mantle of these also bears a pattern of concentric ridges. Young Lehmannia valentiana and Deroceras spp. are especially closely similar in form. However, Deroceras panormitanum and D. reticulatum are never banded, and the sticky mucus of D. reticulatum often becomes milky white when the animal is irritated. A larger species, Limax maximus has a mottled rather than banded mantle and an overall different pigmentation and sticky mucus. Both Limax and Deroceras differ anatomically from Lehmannia (see for example, Quick, 1960).
Within the genus Lehmannia, the size and shape of the penial flagellum is important for identification of species (Waldén, 1961; Quick, 1960; Kerney & Cameron, 1979). L. valentiana is recognized from L. marginata by its short finger-like or slightly bulbous flagellum (Figure 2), not tapered and pointed as in L. marginata.
Acknowledgments
I thank Kristiina Ovaska, Victoria, for supplying the photograph in Figure 1; Kelly Sendall, Collection Manager, Invertebrates, Fish and Herpetology, RBCM, for providing details of his record of this species; and Tammy Forsyth, as always, for her assistance.
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