Re-description of the slug-parasitic nematode Alloionema appendiculatum Schneider, 1859 (Rhabditida: Alloionematidae)

Alloionema appendiculatum is a common juvenile parasite of many terrestrial molluscs. Its third-stage juveniles (dauers) invade the foot muscle of snails and slugs and develop into fourth-stage juveniles, which then leave the host. Later they mature and reproduce in the soil. A population of A. appendiculatum was isolated from infected individuals of the invasive slug Arion vulgaris (= A. lusitanicus), collected in the city of Ceske Budejovice, Czech Republic, and was designated as the AL strain. This nematode is also able to reproduce on pig kidney in laboratory culture. Our isolate was compared primarily with the description published by Mengert (1953) and in some aspects with the original description published by Schneider (1859). Insufficient morphology, morphometrics, phylogeny and an absence of pictorial material encouraged us to re-describe this frequent slug parasite and to add some new information on its life-cycle. The species is characterised by the absence, in adults, of ridges in the lateral fields. At this life stage the stoma is short, narrow and approximately twice as long as it is broad. Fourth-stage female juveniles produce a mucus-like substance from the phasmids. Males possess six pairs of papillae and a single inconspicuous papilla. The nematode has both parasitic and saprophytic life-cycles. Parasitic adults are bigger than the saprophytes and have a thick, digitate tail, whereas the smaller saprophytic generation has a filiform tail. The species is amphimictic, displaying a higher proportion of females, but males are frequent.