Steinernema yirgalemense n. sp. (Rhabditida: Steinernematidae) from Ethiopia

Summary – Steinernema yirgalemense, a new species based on morphological and molecular data, is described from Yirgalem, Ethiopia. This nematode belongs to the ‘bicornutum-group ’ which includes nematodes with horn-like structures in the labial region of the infective juvenile. The new species can be recognised by the infective juvenile having a body length of 635 (578-693) µm, distance from anterior and to excretory pore of 51 (45-59) µm; tail length of 62 (57-67) µm and E % (EP/tail length × 100) of 83 (67-90). The lateral field pattern is variable from anterior to posterior; the formula for the arrangement of ridges from head to tail being: 2, 6, 8, 6, 2. The new species can be further recognised by male characters: spicule with large velum and tapering posteriorly to a point, the ratio SW (spicule length/cloacal body diameter) and GS (gubernaculum length/spicule length) and especially by the presence of 12 pairs of genital papillae plus a single midventral papilla. The 12th pair, located at the edge of the cloacal aperture, is an important character. The presence of a low epiptygma is another diagnostic character of the new species. The new species is a sister taxon to S. abbasi and is characterised by the sequence length of the ITS regions (960 bp), ITS1 (270 bp), ITS2 (284 bp) and also by the pairwise distance of both ITS and D2/D3 regions between species of nematodes in the ‘bicornutum-group’