AQUATIC NEMATODES FROM ETHIOPIA .7. THE FAMILY RHABDOLAIMIDAE CHITWOOD, 1951 SENSU LORENZEN, 1981 (CHROMADORIDA, NEMATODA) WITH THE DESCRIPTION OF UDONCHUS-MERHATIBEBI N-SP

Three species of Rhabdolaimus de Man, 1880 and two (of which one is ne w to science) of Udonchus Cobb, 1913 are described from sediment sampl es of two lakes, two rivers and a hot spring, Ethiopia. Udonchus merha tibebi n.sp. is characterized by a distinctly truncate lip region and small cardia surrounded by gland cells that lie on the anterior intest ine at 45 degrees. The presence of twelve rugae in the cheilostome in the genus Udonchus is reported here for the first time. As a result, t he family Rhabdolaimidae has been moved from suborder Leptolaimina to the superfamily Microlaimoidea in the suborder Chromadorina. The famil y Rhabdolaimidae is also subdivided into the subfamilies Rhabdolaimina e Chitwood, 1951 and Undonchinae n. subfam.. Scanning electronmicrosco pic pictures of the five species viz. R. aquaticus de Man, 1880, R. cf , minor Cobb, 1914, R. terrestris de Man, 1880, U. merhatibebi n.sp. a nd U. tenuicaudatus Cobb, 1913 are also given.