توصیف گونه جدید Oscheius cyrus sp. n. (Nematoda: Rhabditidae) به عنوان نماتد بیمارگر حشرات

Entomopathogenic nematodes (EPNs) are used as biocontrol agents of crop pests with innocuous impact on vertebrates and plants, and they are mutually associated with virulent bacteria. Lately, it has received increased attention to the other members of the Rhabditida, like Oscheius genus, as a new candidate for biological control. In the current study, a new species of the genus Oscheius cyrus sp. n., collected in the moist soils taken from forest heights in the north of Iran, is recorded. A comprehensive description, comprising molecular (ITS and 18S rDNA genes) information, morphometrics data, and LM and SEM images, is supplied. The new species is identified by small- to medium-sized nematodes, 1097-1293 µm long, the lateral field with five incisures, lip region continuous, stoma tubular, and bearing glottoid apparatus without teeth. The pharynx consists of cylindrical corpus gradually enlarging posteriorly, with oval-shaped median bulb, and basal bulb bearing a haustrulum. Secretory–excretory pore is sclerotized, the female genital system is didelphic–amphidelphic, with equatorial vulva. Vulva is without epiptigma and female rectum conspicuously longer than anal body diameter. Female tail is conical elongate with fine tip, and phasmid posterior to anus, about 42-45% of tail length. The new species, fall under the genus Oscheius as it has tubular stoma without teeth. The species resembles O. myriophilus, however it differs in the upper range for female body length, female tail, infective juvenile tail length, and lateral field number. It was distinguished from its closest relative, O. insectivore, by the general lip region. The male was not found. Molecular analysis showed that the new species has the most similarity to O. myriophilus both in the ITS and 18S region. Morphological and molecular data confirmed its belonging to the Insectivora-group. Furthermore, the species of Ochrobactrum pseudogrignonense was reported as a dominant associated bacterium of the new Oscheius species. Finally, the mortality of the host after seven days varied from 20% to 82.5%, depending on nematode concentrations.