Aquatic nematodes from Ethiopia .6. The genera Chronogaster Cobb, 1913, Plectus Bastian, 1865 and Prismatolaimus de Man, 1880 with descriptions of C-ethiopica n sp and C-getachewi n sp (Chromadorida: Nematoda)

Five species belonging to three genera viz. Chronogaster Cobb, 1913, Plectus Bastian, 1865 and Prismatolaimus de Man, 1880, two of which are new to science are described from a hot spring, Rivers Abbay and Gelda and Lake Tana, Ethiopia. Chronogaster ethiopica n. sp., in its possession of a ventral mucro, comes close to a number of species but differs from all hitherto known species in a combination of characteristics: its possession of crystalloid bodies, vacuolated lateral glandular bodies, horse-shoe-shaped amphids and spineless tail terminus, and its lack of longitudinal lateral lines. C. getachewi n. sp. is a unique species in the genus in having more than 100 vacuolated lateral glandular bodies and a dorsal mucro that emerges from the tail terminus about 1.5 mu m from the tail tip. Detailed descriptions of C. multispinatoides Heyns & Coomans, 1984, Plectus (Plectus) galapagensis De Ley & Coomans, 1994, and Prismatolaimus matoni Mulk & Coomans, 1979 are given. The most important characteristics in the specific identifications of the genus Chronogaster are discussed. These most important characteristics of the seventeen species described after the first review of the genus by Heyns & Coomans (1980) are reviewed in the form of tables and illustrations. Additional information on the morphology of the genus generated after the first review is particularly dealt with. In addition, SEM pictures of C. getachewi n. sp., C. multispinatoides, P. (P.) galapagensis and P. matoni are presented. Furthermore, SEM pictures of a population of C. magnifica Andrassy, 1956 from Ivory Coast are included.