TERRESTRIAL NEMATODES FROM THE GALAPAGOS ARCHIPELAGO .7. DESCRIPTION OF TYLOCEPHALUS-NIMIUS SP-N AND NEW DATA ON THE MORPHOLOGY, DEVELOPMENT AND BEHAVIOR OF TYLOCEPHALUS-AURICULATUS (BUTSCHLI, 1873) ANDERSON, 1966 (LEPTOLAIMINA, PLECTIDAE)

Tylocephalus nimius sp.n, is described from Isla Santa Cruz and Isla F loreana. It has cornua measuring 12-14 mu m and cervical expansions ex tending well posterior to the anteriormost somatic setae. The known sp ecies 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 indepen dent of body locomotion. The hypothesis is proposed that this behaviou r is functionally linked to the expanded and flattened lip region, and that T. auriculatus and other Wilsonematinae are specialized in sweep ing 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 r egion during the first and second moult.