A New Species of Pristionchus (Rhabditida: Diplogastridae) and Its Bacterial Symbiont from Yixing, China.

A new nematode species, Pristionchus entomophilus n. sp., was collected during a soil sample survey in Yixing of Jiangsu province, eastern China. P. entomophilus n. sp. is distinguished by its unique characteristics. This new species is mainly hermaphroditic, with males seldom found. The new nematode has a similar body length but has much narrower body width compared with P. pacificus. Its body is covered with longitudinal ridges: 12 ridges on head, 13 or 14 ridges in the middle, 11 and 7 ridges in front and rear of the anus, respectively. The eurystomatous form mouth includes a triangular dorsal tooth, a large claw-like right subventral tooth, and a row of five ventral denticles placed opposite the dorsal tooth. Only eight pairs of genital papillae and a pair of phasmids are present in the tail of the male as the sixth pair of papillae having seemingly been degenerated and lost. Molecular phylogenetic trees based on 18S rDNA confirmed that the new species belongs to the genus Pristionchus and is most closely related to P. pacificus. Moreover, the new species was found to be occasionally associated with the entomopathogenic bacterial strain 09FLYB1 of Serratia nematodophila and be able to stably transfer the bacterial strain for several generations.