First record of Deroceras invadens Reise, Hutchinson, Schunack & Schlitt, 2011 (Gastropoda: Pulmonata: Agriolimacidae) from the island of Newfoundland, Canada

: The introduced European slug reported verified record for


First record of Deroceras invadens
Agriolimacidae) from the island of Newfoundland, Canada Deroceras invadens Reise, Hutchinson, Schunack & Schlitt, 2011 was recently described for a species of terrestrial slug that has previously been called D. panormitanum (Lessona & Pollonera, 1882) or Agriolimax caruanae (Pollonera, 1891). Neither of these names is applicable to the invasive species that presumably originated from the Mediterranean region but now has an almost worldwide distribution (Reise et al. 2006(Reise et al. , 2011. There are just a few species of Deroceras Rafinesque, 1820, in North America in addition to the invasive D. invadens. Deroceras laeve (Müller, 1774), which may include the enigmatic west coast species D. hesperium Pilsbry, 1944(Wiktor 2000Roth et al. 2013), is widespread and generally considered a native species, although there is speculation that some populations could be introduced (Grimm et al. 2010). Deroceras reticulatum (Müller, 1774) is unquestionably an introduction and is now very widespread (Grimm et al. 2010). Both D. reticulatum and D. invadens are agricultural pests (Baker 1999;Reise et al. 2005).
Among species of Deroceras in North America, D. invadens is most similar to D. laeve (Reise et al. 2006). Both are smaller and darker than D. reticulatum and without the firmer body, thicker skin, and sticky, milky white mucus when irritated (Grimm et al. 2010). Reise et al. (2006) noted that some North American morphs of D. laeve are not separable by external appearance from D. invadens. Deroceras invadens is distinguished from D. laeve by morphological differences of the distal reproductive system (sensu Reise 2007), that is, of the penis and associated structures. The penis of D. invadens is strongly and equally bilobed. Between the lobes of the penis, there is a cluster of usually 4-6 finger-like glands (Forsyth 2004;Grimm et al. 2010;Reise et al. 2011) (Figure 1). Partial or total loss of the male reproductive organs is common for D. laeve, but when a penis is present, it is a long, somewhat contorted structure with a twisted terminal gland (Pilsbry 1948;Wiktor 2000). There is no cluster of finger-like glands.
On 6  At the time of collection, eight Deroceras slugs were suspected to be D. invadens, based on the habitat type. Animals were grey-brown, watery, thin-skinned, and not confidently separable from D. laeve (a species not found at the site). Later, dissections revealed the strongly bilobed penis and cluster of glands of this species, confirming the identity as D. invadens (Figure 1).
Deroceras invadens is now widely distributed to many places worldwide (Reise et al. 2006(Reise et al. , 2010 and has been   (Grimm et al. 2010). Greenhouse records (white circles): Montreal and Sherbrooke, Quebec (Chichester and Getz 1969). found three or possibly four Canadian provinces (Figure 2). Under the names Deroceras panormitanum or D. caruanae, D. invadens has been known in North America for at least seven decades, having been first noticed in California in 1940 (Pilsbry 1948). In western North America, it is now rather well known from southern British Columbia to California (Grimm et al. 2010;Burke 2013), as well as Colorado (Reise et al. 2006). However, aside from a few reports from greenhouses, it was unknown from outof-doors in eastern North America until recently found in Washington, D.C. (Reise et al. 2006). The first eastern North American and first Canadian records of this species was by Chichester and Getz (1969) who recorded it from two greenhouses in Montreal and Sherbrooke, Quebec. No other well-documented records exist for eastern Canada. Although Grimm et al. (2010) wrote that the species was found in Kingston, Ontario, they were unable to provide further data and in the absence of specimens could not verify the identification.
The present report of Deroceras invadens from St. John's, Newfoundland, is a new record for the province of Newfoundland and Labrador, the first from Atlantic Canada, and the first verified record from outside of greenhouses in eastern Canada. The closest previously reported locality for D. invadens is the decades-old greenhouse record from Sherbrooke, Quebec (Chichester and Getz 1969).
Deroceras invadens lives in synanthropic habitats, along roadsides and in gardens, farms, nurseries and greenhouses and other disturbed and unkempt sites in cities and suburbs (Kerney 1999;Forsyth 2004;Reise et al. 2006Reise et al. , 2011Burke 2013). Its presence in North America is probably under-recorded, and Reise et al. (2006) suggested that it is more widespread east of the Continental Divide than currently known. This species has probably been under-reported because of a general lack of interest in the slug fauna of cities and other disturbed habitats, as well as the great similarity to D. laeve that necessitates dissections to confirm identity. As noted by Reise et al. (2006), there is a need to record introduced terrestrial molluscs in North America and provide a baseline for future studies on these species' spread. It is anticipated that more searches in Newfoundland and elsewhere in eastern Canada may yield additional sites.