Review of the genus Helicotylenchus Steiner, 1945 (Nematoda: Hoplolaimidae) with updated diagnostic compendium

A compendium of the genus Helicotylenchus based on 16 diagnostic characters to separate Helicotylenchus species viz., habitus, body length, ratios a, c, c ́, vulva position, DGO from base of stylet knobs, stylet length, shape of stylet knobs, shape of head, number of head annules, shape of tail, number of tail annules, position of phasmid in relation to anus, presence of male and female posterior genital branch is presented. These allometric and morphometric characters were derived from the original descriptions. An up to date list of 230 valid nominal species from world along with available illustrations and 32 species from Pakistan with diagnostic key is provided.