POPULATIONS OF PLECTUS-ACUMINATUS BASTIAN, 1865 AND PANAGROLAIMUS-MAGNIVULVATUS N-SP (NEMATODA) FROM NUNATAKKS IN DRONNING-MAUD-LAND, EAST ANTARCTICA

Populations of Plectus acuminatus Bastian, 1865 and Panagrolaimus magn ivulvatus n. sp. from East Antarctic nunatakks are described from stud ies by light and scanning electron microscopy. The populations of Plec tus found are close to P. acuminatus, P. antarcticus de Man, 1904 and P. cirratus Bastian, 1865 and their identity is discussed. Additional information on the morphology of P. acuminatus is provided. The new sp ecies of Panagrolaimus is separated from other species of the genus by the extreme development of the vulval lips, especially the anterior l ip. It is further separated from the most closely related species, P. superbus Fuchs, 1930, by a larger corpus/isthmus-ratio and a more post erior position of the phasmids in the females, and larger spicules in the males.