Heterorhabditis georgiana n. sp. (Rhabditida: Heterorhabditidae) from Georgia, USA

In a survey of entomopathogenic nematodes in Georgia, a nematode isolate of the genus Heterorhabditis was collected from soil by the insect-baiting technique and maintained in the laboratory on last instar Galleria mellonella (L.) larvae. Morphological and molecular studies of the isolate showed that the nematode is a new species. Light and scanning electron microscopy, DNA characterisation and phylogeny were used for this description. Heterorhabditis georgiana n. sp. is morphologically similar to H. bacteriophora and can be distinguished from this species mainly by male and female characters. Sixty percent of males have three pairs of papillae in the terminal group; 40% with three papillae on one side and two papillae on the other. The tail is conoid and slightly curved ventrally. The percentage of the gubernaculum to spicule length (GS%) is similar to that of H. mexicana (56) but higher than that of H. bacteriophora and species in the indica-group and the length of the spicule relative to anal body diam. (SW%) is lower than that of H. baujardi (172 vs 182), H. indica (172 vs 187) and H. bacteriophora (172 vs 174), but higher than that of H. amazonensis (172 vs 152), H. floridensis (172 vs 157) and H. mexicana (172 vs 167). The female can be differentiated from related species by its unique vulva pattern. In phylogenetic trees of ITS and D2D3 regions, the new species and H. bacteriophora form a monophyletic group. The new species has evolved five autapomorphic nucleotide character states based on analysis of ITS, differing from its sister taxon H. bacteriophora at 29 and three aligned positions of ITS and D2D3 regions, respectively.