AQUATIC NEMATODES FROM ETHIOPIA .6. THE GENERA CHRONOGASTER COBB, 1913, PLECTUS BASTIAN, 1865 AND PRISMATOLAIMUS DE-MAN, 1880 WITH DESCRIPTIONS OF CHRONOGASTER-ETHIOPICA N-SP AND CHRONOGASTER-GETACHEWI N-SP (CHROMADORIDA, NEMATODA)

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