Terrestrial nematodes from the Galapagos Archipelago .7. Description of Tylocephalus nimius sp n and new data on the morphology, development and behaviour of T-auriculatus (Butschli, 1873) Anderson, 1966 (Leptolaimina:Plectidae)

Tylocephalus nimius sp.n, is described from Isla Santa Cruz and Isla Floreana. It has cornua measuring 12-14 mu m and cervical expansions extending well posterior to the anteriormost somatic setae. The known species T. auriculatus is described from soil and from a derived culture. On agar, T. auriculatus swings its lip region dorsally and ventrally during feeding, in a continuously oscillating sweeping motion independent of body locomotion. The hypothesis is proposed that this behaviour is functionally linked to the expanded and flattened lip region, and that T. auriculatus and other Wilsonematinae are specialized in sweeping up bacteria attached to flat microsurfaces in soils. Furthermore, morphological and developmental observations suggest that the species has only three juvenile stages, with marked metamorphosis of the lip region during the first and second moult.