Abstract
A new amphimictic species Oscheius indicus n. sp. is described and illustrated with morphological and molecular data. The species is characterized by a medium-sized and slender body (female: L = 1.1 to 1.5 mm; a = 16.8 to 20.6; b = 5.7 to 7.1; c = 7.5 to 10.4; c’ = 5.0 to 7.6; V = 45 to 51%), presence of four incisures each in the lateral fields with three minute warts, long rectum (2 to 3 anal body diameters), nine pairs of papillae arranged as 1+1+1/3+3 pattern, a prominent double-flapped epipytigma on vulval opening, presence of open leptoderan bursa and crochet needle-shaped spicules place it in the insectivora group. Morphologically, O. indicus n. sp. closely resembles O. carolinensis, O. chongmingensis, O. colombiana, and O. nadarajani. Molecular phylogenetic analysis carried out using ITS and D2/D3 expansion region of 28S rDNA sequences suggests that O. indicus n. sp. is closer to O. chongmingensis and O. rugaonensis. In summary, the morphometrical data, morphological observations and molecular phylogenetic analysis suggested that O. indicus n. sp. is sufficiently different from any known species and is therefore proposed as a new species within the insectivora group.
Highlights
Oscheius is a free-living bacteriophagous or entomopathogenic nematode found in saprobic biotypes, occasionally associated with beetles (Lucanidae). Körner (1954) first described Rhabditis insectivora
Molecular phylogenetic analysis carried out using ITS and D2/D3 expansion region of 28S rDNA sequences suggests that O. indicus n. sp. is closer to O. chongmingensis and O. rugaonensis
The genus Oscheius has a large number of species which are morphologically very close to each other
Summary
Oscheius is a free-living bacteriophagous or entomopathogenic nematode found in saprobic biotypes (detritus, dung), occasionally associated with beetles (Lucanidae). Körner (1954) first described Rhabditis insectivora. On the basis of morphological and molecular studies, Sudhaus (2011) characterized the family Rhabditidae by generalized body plan into three groups, Pleiorhabditis, Synrhabditis, and Anarhabditis He positioned the genus Oscheius under the group Synrhabditis which consisted of 27 valid species, of which species belonged to dolichura group and to insectivora group. The genus Heterorhabditidoides was proposed as a separate genus (Zhang et al, 2008) but it was later considered a junior synonym of Oscheius (Ye et al, 2010) Another species, Heterorhabditidoides rugaoensis, was transferred to Oscheius (Darsouei et al, 2014; Tabassum et al, 2016). We describe the 45th species of the genus, Oscheius indicus n. sp
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