Morphological and molecular characterisation of two free-living bacterivorous nematodes belonging to Rhabditida from South Africa

A new population of Pseudacrobeles (Pseudacrobeles) macrocystis and Poikilolaimus oxycercus is described from South Africa. Poikilolaimus oxycercus was collected from soil covered by a natural grass in South Africa, which is morphologically similar to the original description. The South African population of P. oxycercus is characterised by having a small size (807-818 mu m in males and 703-779 mu m in males), female tail cupola-shaped (24-35 mu m), and spicule length (27-35 mu m). The South African population of P. (P.) macrocystis, collected from natural grass, is characterised by having a small size (611-786 mu m), a lateral field with three incisures, lip region with lips bearing seta-like processes and blunt conoid labial probolae, primary and secondary axils smooth, nerve ring and excretory pore at the posterior part of the pharyngeal corpus, spermatheca well developed, postvulval uterine sac poorly developed, female tail conoid-elongate, male tail conoid with thin acute mucro and spicules small (31-36 mu m). Measurements and line illustrations of the species are given. In addition, LM, SEM photographs and the phylogenetic position of P. (P.) macrocyctis are provided. The 18S and 28S rDNA analyses show that P. macrocystis is closely related to other species of the genus Pseudacrobeles having lips with seta-like processes. This is the first report of P. (P.) macrocystis from South Africa.