| Insectivorous nematodes are a kind of parasitic nematodes,include a great variety of species belonging to 18 families of 5 orders in the phylum Nematoda,and distributed widely.According to incomplete statistics,there are more than 1000 nematode species that can parasitize about 700 species of insects.Some nematode species or genera of families Steinematidae,Heterorhabditidae,Mermithidae and Rhabditidae,have enormous potential to control pests.Two strains of insectivorous nematodes,CM 19 and N3,isolated from the Yangtze River Delta Basin,were identification by morphology characteristics combined with molecular biology data,pathogenicity and symbiotic relationship analysis with their symbiotic bacterial strains.Our results indicated that CM 19 was a potential entomopathogenic nematode belonging to the genus Oscheius,and N3 a new species of the genus Diplogasteroides.Strain CM 19 was morphologically very similar to O.myriophila,but can be distinguished from it and other species of Oscheius on the basis of unique morphological characteristics of the bursa as well as males’ papillae.The males’ bursal papillar formula is 2,1,3,3 with everted tips of the first,fifth and seventh pairs.The bursal rim is jagged and joined together in front of the spicules,partially extended and decorated with microvilli.The spicules are incompletely separated,and the tail does not extend beyond the bursa.Phylogenetic trees of 18S rDNA and ITS indicate that Strain CM 19 belongs to the insectivora-group of the genus Oscheius;it is most closely related to O.myriophila,and the two species can be distinguished on the basis of their different body length,morphological features of the bursa,and molecular data.Strain CM 19 is associated facultatively with a symbiotic bacterial strain of Serratia.The LC50 of this novel putative entomopathogenic nematode against Galleria mellonella was 69,1 IJs/ml in 48 hours of infection.Phylogenetic tree of 18S rDNA indicated that strain N3 belong to the genus Diplogasteroides and have most closely relationship with Diplogasteroides nasuensis.The 18S rDNA sequences of the two nematodes only share 90.8%identity.The body length of N3 is longer than D.nasuensis.The greatest body diam of N3 is shorter than D.nasuensis.The mouth length of male of N3 is longer than the female,whereas those of D.nasuensis are completely different.The spicule length of male individual of N3 is shorter than D.nasuensis.There are also some significantly differences between the two species,such as the base form of spicule,adherent position of gubernaculum and etc.In view of the great morphology and molecular data difference existing among the two closest related species,strains N3 should be a new species of the genus Diplogasteroides. |
