Steinernema indicum n. sp., a new entomopathogenic nematode (Nematoda: Steinernematidae) from India

Abstract

A new species of entomopathogenic nematode, Steinernema indicum n. sp., was isolated from a coconut palm (Cocos nucifera) field in the district of Udupi, Karnataka, India. The infective juveniles (IJ) of S. indicum n. sp. possess a body length of 1043 (869-1172) μm. The lateral fields are formed by eight equally spaced and developed ridges (nine incisures) in the mid-body region, giving the formula 3, 8, 7, 5. The excretory pore is located posterior to the mid-pharynx region (D% = 63), and the hyaline region occupies ca half of the tail length. The first-generation males are characterised by very short spicules 66 (60-70) μm long. The male spicules are moderately curved with a sharp tip and are golden-brown in colour with the manubrium elongate and with a length to width ratio of 1.92:1. There are 11 pairs of genital papillae plus a single midventral papilla located anterior to the cloacal region. The first-generation male of S. indicum n. sp. is characterised by the presence of a single dorsal postcloacal papilla, a typical diagnostic character that has not been reported from any other steinernematid species. The first-generation male tail has a short mucron present in ca 40% of specimens examined and a second-generation male tail showing a short mucron present in ca 65% of male specimens examined. The first and second-generation females possess a slightly protruding post-anal swelling. The new species is further characterised by sequences of the internal transcribed spacer (ITS) and partial 28S regions (D2-D3) of the ribosomal DNA (rDNA). Phylogenetic analyses confirm that S. indicum n. sp. belongs to the glaseri-group and, based on both ITS and D2D3 genes, showed that S. indicum n. sp. is a member of the karii clade.