New genera and species of nematode parasites (Drilonematoidea: Ungellidae) from coelomic cavity of Neotropic acanthodrilids deposited in the Natural History Museum of Geneva, Switzerland

Two new genera and two new species of nematodes (Ungellidae, Drilonematoidea) parasitic in Neotropic acanthodrilids from the collection of the Natural History Museum of Geneva, Switzerland, are described. Yagansiella longicollis gen. n., sp. n. and Ungella chileana sp. n. are parasitic in Yagansia spatulifera, whereas Ungella micronychium sp. n. in Y. diversicolor and Patagoniella capitoporus gen. n., sp. n. in Y. papillosa. Yagansiella longicollis gen. n., sp. n. resembles Ungella in general morphology but differs by anterior position of ovary top cell and posterior vulva position, characteristic body and caudal fimbriate organs shape. U. chileana sp. n. is distinguished by large circular fimbriate organs in tail, female body shape and arrangement of female genital tube and spicule shape. Ungella micronychium sp. n. differs by minute cephalic hooks and shape of fimbriate organs and spicules and gubernaculum. Patagoniella capitoporus gen. n., sp. n. is distinguished by anteriormost position of excretory pore, anterior vulva position and shape of fimbriate organs and spicules and gubernaculum.