Several species of European slugs are invasive in the USA, threatening native species and damaging agricultural and horticultural crops. One possible explanation for the success of these invaders is parasite release. To test this hypothesis we collected European slugs in part of their native range (United Kingdom) and in the USA and compared prevalence, distribution and species richness of their nematode parasites. All slugs were dissected and examined for the presence of nematodes. In the UK, nematodes were present at 93% of study sites and 16.4% of all slugs examined were associated with nematodes whereas in the USA the respective figures were 34% of sites and 5.4% of slugs. Nematode species richness was greater in the UK with 12 species being found, seven of which were thought to be truly parasitic as opposed to being phoretic or necromenic. Nine species of nematode were found in the USA, four of which were truly parasitic. Four of the ten European slug species examined in the USA, were entirely free of truly parasitic nematodes whereas all were infected by nematodes in some sites in the UK. There was a significant difference in the prevalence of truly parasitic nematodes in five of these species when comparing their home versus invasive range. A significant difference in parasite prevalence was observed when comparing native and introduced slug species in the USA, however, this was not significant in the UK. Our data support a role for parasite release during the invasion of the USA by European slugs.Electronic supplementary material The online version of this article (

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A survey of nematodes associated with terrestrial slugs was conducted for the first time in Norway. A total of 611 terrestrial slugs were collected from 32 sample sites. Slugs were identified by means of morphological examination, dissection of genitalia and molecular analysis using mitochondrial DNA. Twelve slug species were identified, representing four different slug families. Internal nematodes were identified by means of morphological analysis and the sequencing of the 18S rRNA gene. Of the sample sites studied, 62.5% were found to be positive for nematode parasites, with 18.7% of all slugs discovered being infected. Five nematode species were identified in this study: Alloionema appendiculatum, Agfa flexilis, Angiostoma limacis, Angiostoma sp. and Phasmarhabditis hermaphrodita. Of these species, only one nematode was previously undescribed (Angiostoma sp.). This is the first record of the presence of A. appendiculatum, A. flexilis and A. limacis in Norway.

Two new species of Angiostoma Dujardin, 1845 taken from the intestines of terrestrial molluscs (Gastropoda: Stylommatophora) collected in the UK are described and illustrated. Angiostoma milacis n. sp. is parasitic in milacid and agriolimacid slugs and is closely related to A. asamati Spiridonov, 1985. Angiostoma zonitidis n. sp. was found in a zonitid snail and is most closely related to A. kimmeriense Korol & Spiridonov, 1992 (emend.), a species also from zonitid snails. An amended generic diagnosis is proposed. The distribution of A. limacis and A. milacis sp. n. in hosts is discussed and a key to the species of Angiostoma is presented.

Summary Phasmarhabditis quinamensis sp. n. was recovered from several tropical terrestrial gastropod species collected in Cat Tien National Park in southern Vietnam with the snail, Sesara sp., designated as the type host. Phasmarhabditis quinamensis sp. n. is recognised by males and females with a lip region set off by the circle of six triangular low probolae, three bilobed, separated lips, stoma nearly as wide as long, the first genital papilla in males not incorporated into the bursa, the ensheathed dauer juveniles more than 1 mm long and with two circles of papillae at the head end and prominent amphidial apertures, a long filamentous tail and, when exsheathed, with a short, conical tail ending with two tiny spikes. The head structure of P. quinamensis sp. n. differentiates it from all nominal species of Phasmarhabditis. Phasmarhabditis quinamensis sp. n. is the second species of the genus found in Cat Tien National Park. The sympatric species P. meridionalis was also found during the present study. Phylogenetically, both species belong to different lineages within Phasmarhabditis. The molecular analysis based on partial sequences of LSU rDNA, and ITS rDNA regions showed P. kenyaensis to be the closest species to P. quinamensis sp. n.