Heterorhabditis pakistanense n. sp. (Nematoda: Heterorhabditidae) a new entomopathogenic nematode from Pakistan

A new entomopathogenic nematode species of Heterorhabditis, described as H. pakistanense n. sp., was isolated from soil samples around the roots of grass at Malir, Karachi, Sindh, Pakistan. The new species is characterized morphologically by features of males: body size 819 μm (720–1013 μm), D% ((distance from anterior end to excretory pore divided by pharynx length) × 100) 119 (110–126), SW% ((spicule length divided by anal body diameter) × 100) 156 (144–191), GS% ((gubernaculum length divided by spicule length) × 100) 58 (48–65) and variations in the number of bursal papillae of the terminal group: 8th and 9th papillae sometimes absent on both sides, sometimes eight papillae present on the right side whereas six papillae present on the left side. On the right side the arrangement of papillae is 1 + 2 + 3 + 2 whereas on the left side it is 1 + 2 + 3. The hermaphrodite has a prominent post-anal swelling and a conoid tail 82 μm (64–95 μm) long with a pointed terminus. Hermaphrodites of H. pakistanense n. sp. can be distinguished from all species of Heterorhabditis except H. downesi by having a mucronate tail. Infective juveniles have a medium-sized body (581 μm (558–624 μm)), long pharynx (117 μm (113–125 μm)), ensheathed tail (99 μm (95–110 μm)) and E% ((distance from anterior end to excretory pore divided by tail length) × 100) 100 (95–107). The new species can be distinguished from all species of Heterorhabditis by the absence of the 7th, 8th and 9th bursal papillae. Heterorhabditis pakistanense is further characterized by the internal transcribed spacer (ITS) and the D2D3 region of the 28S rDNA gene. The closest species H. indica, H. gerrardi, H. amazonensis and H. noenieputensis being separated by 9, 7, 66 and 15 bp, respectively, in the ITS region. Molecular phylogenetic trees based on sequences of ITS rDNA, D2D3 regions and the mitochondrial 12S rRNA gene support the description of H. pakistanense as a new species.