Steinernema everestense n. sp. (Rhabditida: Steinernematidae), a new species of entomopathogenic nematode from Pakhribas, Dhankuta, Nepal

Abstract

A new species of entomopathogenic nematode, Steinernema everestense n. sp., was recovered from soil samples collected from Pakhribas, Dhankuta district of Nepal, during a survey in 2007. The analysis of ITS-rDNA and D2D3 LSU sequences placed S. everestense n. sp. in the feltiae-kraussei-oregonense group. The nematode can be separated from other described species of Steinernema by morphological and morphometric characteristics and by characterisations and phylogeny inferred from DNA sequences of the D2D3 LSU or ITS regions of rDNA. For infective juveniles, the new species can be recognised by the body length of 775 (705-838) μm, pharynx 119 (110-130) μm long, H% = 61 (47-68) and E% = 78 (60-89). The lateral field pattern is 2, 8, 6, 4, 3. The males have well curved, brownish-yellow spicules with a prominent but short velum, gubernaculum plump, boat-shaped to almost straight in lateral view, cuneus long, needle-shaped, corpus with two wings in ventral view. Spicule and gubernaculum length of the first generation males is 79 (65-87) μm and 50 (39-57) μm, respectively. A tail mucron is present in both male generations. Genital papillae total 23 or 25, comprising 11 or 12 pairs and a single midventral papilla. Specimens with 23 genital papillae have eight precloacal pairs (seven pairs subventral and one pair lateral), two pairs subterminal and one pair subdorsal. The most posterior two pairs are consistently located near the tail tip. The specimens with 25 genital papillae have an extra adcloacal pair of papillae and the anteriormost two pairs are close together. The vulva is slightly protruding, mostly with equal lips, and low epiptygmata. A post-anal swelling is developed in most first and all second generation females.