Summary A new species of entomopathogenic nematode, Steinernema borjomiense n. sp., was isolated from the body of the host insect, Oryctes nasicornis (Coleoptera: Scarabaeidae), in Georgia, in the territory of Borjomi-Kharagauli. Morphological characters indicate that the new species is closely related to species of the feltiae-group. The infective juveniles are characterised by the following morphological characters: body length of 879 (777-989) μm, distance between the head and excretory pore = 72 (62-80) μm, pharynx length = 132 (122-142) μm, tail length = 70 (60-80) μm, ratio a = 26.3 (23.0-29.3), H% = 45 (40-51), D% = 54 (47-59), E% = 102 (95-115), and lateral fields consisting of seven ridges (eight incisures) at mid-body. Steinernema borjomiense n. sp. was molecularly characterised by sequencing three ribosomal regions (the ITS, the D2-D3 expansion domains and the 18S rRNA gene) and the mitochondrial COI gene. Phylogenetic analyses revealed that S. borjomiense n. sp. differs from all other known species of Steinernema and is a member of the monticolum-group.

Abstract:A new species of entomopathogenic nematode (EPN), Steinernema tbilisiensis sp. n. is described. The species was isolated from soil samples of the deciduous forest located in the Tbilisi area. Morphological and morphometric data as well as phylogenetic analysis show that S. tbilisiensis sp. n. belongs to the group S. affine/intermedium. S. tbilisiensis sp. n. has been attributed to the group S. affine/intermedium on the basis of spicule and gubernaculum structure. The new species differs from other species of S. affine/intermedium group in the following diagnostic characters: the spicule of S. tbilisiensis sp. n. is the smallest and the gubernaculum of S. tbilisiensis sp. n. is shorter than other species of the S. affine/intermedium group. Infective juveniles (IJs) of S. tbilisiensis sp. n. are distinguished by a relatively long body (L = 866 µm), the position of excretory pore (EP = 72 µm), the length of the esophagus (ES = 140 µm) and the length of the anal body width (ABW = 25 µm). IJs of S. tbilisiensis sp. n. have four lateral lines like S. beddingi, but the number of lines is six in S. affine, S. sichuanense and S. intermedium. Also the analysis of rDNA (28S and ITS) gene sequences depicts this Steinernema species as a distinct and unique entity. The symbiotic bacteria of S. tbilisiensis sp. n. was isolated and found to be Xenorhabdus bovienii using a multigene approach.