Abstract
Angiostoma norvegicum n. sp. (Angiostomatidae) is described from the oesophagus, crop and the buccal mass of five species of slugs of the family Arionidae, Arion vulgaris (Moquin-Tandon), Arion ater (L.), Arion fasciatus (Nilsson), Arion fuscus (Müller) and Arion rufus/Arion ater hybrid), collected throughout Norway. Angiostoma norvegicum n. sp. was found parasitising arionids at seven of the 30 sample sites examined (23.3%), and 9.9% of all Arion spp. were infected with this nematode. The new species is characterised by its large size (4.0–8.6 mm long) and in having: lateral alae; 6 + 6 papillae at the cephalic end; a large circular mouth aperture; a spacious stoma; a pharyngeal basal bulb without valvular apparatus; an excretory pore near the base of bulb; a distal part of posterior ovary always outstretched; an anterior ovary distally nearly always outstretched; a vulva situated anterior to mid-body; long, nearly straight spicules and a small gubernaculum; three circumcloacal papillae and caudal genital papillae (GP) arranged in a pattern 1+2/3+3 with GP 5 and GP 8 opened on dorsal side of narrow bursa not reaching tail tip; short conical tails in both sexes with tips supplied by 4 short, unequal denticles. Morphologically, A. norvegicum n. sp. is similar to Angiostoma limacis Dujardin, 1845, which diagnostic characteristics are given based on examination of specimens from Norway and the UK. Conversely, the phylogenetic analyses based on D2D3 large subunit (LSU) rRNA gene sequences performed in the present study did not support the morphological affinity of these two species. Phylogenetic analyses demonstrated that although Angiostoma spp. cluster together, A. norvegicum n. sp. forms a tight monophyletic clade with the milacid nematode parasites Angiostoma margaretae Ross, Malan & Ivanova, 2011 and Angiostoma milacis Ivanova & Wilson, 2009.
Highlights
The association between nematodes and terrestrial molluscs is poorly understood; their host specificity, diversity of specialisations and mechanisms of infection, indicate that their affiliation is both ancient and widespread (Morand et al, 2004)
General data on the occurrence of A. norvegicum n. sp. and other slug-parasitic nematodes in Norway were given in Ross et al (2016) where the new species was designated as Angiostoma sp
Angiostoma norvegicum n. sp. was found parasitising five out of seven species of Arionidae at 23.3% of sample sites (Table 1)
Summary
The association between nematodes and terrestrial molluscs is poorly understood; their host specificity, diversity of specialisations and mechanisms of infection, indicate that their affiliation is both ancient and widespread (Morand et al, 2004). International surveys conducted in Europe, North America, Australasia and Africa (Ross et al, 2016), indicate that there are eight families of nematodes that use terrestrial molluscs as definitive hosts, i.e. the Agfidae Dougherty, 1955, Alaninematidae Theodorides, 1957, Alloionematidae Chitwood & McIntosh, 1934, Angiostomatidae Blanchard, 1895, Cosmocercidae Railliet, 1916, Diplogastridae Micoletzky, 1922, Mermithidae Braun, 1883 and Rhabditidae Orley, 1880 (see Pieterse et al, 2016; Ross et al, 2016). During a survey of nematodes associated with terrestrial slugs in Norway (Ross et al, 2016), a new species of Angiostoma was found together with Phasmarhabditis hermaphrodita (Schneider, 1859) Andrassy, 1983, Agfa flexilis (Dujardin, 1845), Alloionema appendiculatum Schneider, 1859 and another species of the same genus, Angiostoma limacis
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