The strepsipteran parasite Elenchus japonicus (Strepsiptera, Elenchidae) of planthoppers consists of three genotypes

The twisted-wing parasite Elenchus japonicus is a major parasitoid of rice planthoppers (Hemiptera: Delphacidae), including the brown planthopper Nilaparvata lugens , the white-backed planthopper Sogatella furcifera , and the small brown planthopper Laodelphax striatellus . Another Elenchus species, E. yasumatsui , which is considered to be synonymous with E. japonicus , has also been described in southern Asia. However, limited biological and molecular data on this important parasitoid of rice planthoppers are available. In this study, E. japonicas -stylopized planthoppers were obtained from various regions in Asia and Japan. Sequences of the nuclear 18S ribosomal RNA gene and the mitochondrial cytochrome oxidase I gene of the strepsipterans were analyzed from 40 samples of E. japonicus : 14 from N. lugens , 6 from S. furcifera and 20 from L. striatellus . Sequence analysis of these samples revealed three genotypes of E. japonicus . Of the three types of E. japonicus , one was isolated only from L. striatellus from northern Japan. The other two types were found in all three rice planthopper species collected from a wide area in Asia. These results suggest that the three different genotypes of Elenchus can be associated with a particular geographical region and/or planthopper species. The relationship between two previously described Elenchus species and the present three genotypes needs to be elucidated.