Chromadoridae (Chromadorida: Nematoda) from the Indian Ocean: difficulties in morphological identification of Actinonema Cobb, 1920 and Rhips Cobb, 1920

The diagnostic characteristics of Actinonema Cobb, 1920 and Rhips Cobb, 1920 are reviewed and their importance for genera diagnosis assessed. Three species of Actinonema and one species of Rhips are described. Actinonema longicaudatum Steiner, 1918 is characterised by short (2-3 mu m long) anterior sensilla, cylindrical body with a rather narrow anterior end, lateral alae with inverted 'V'-patterns, wide (70-75 of cbd) double amphids and accessory pieces composed of only the telamon which is broad anteriorly and tapers on the posterior and a long tail. Actinonema paraceltica is characterised by long (4-5 mu m) anterior sensilla, large amphids (83-88% of cbd), lateral differentiation of 'V' pattern on each annule and accessory pieces with telamons that have short extensions. Actinonema smolae sp. n. is characterised by long and thin body, large amphids located close to the anterior end and six solid cones. Rhips reginae n.sp. is characterised by six solid cones, large (90% cbd) amphids, lateral differentiation of two longitudinal rows of dots and double jointed spicules