Occurrence of two species of Bursaphelenchus (Nematoda: Aphelenchoididae) in the reproductive organs of Monochamus saltuarius (Coleoptera: Cerambycidae)

Abstract

Summary To clarify the species composition and residency of Bursaphelenchus nematodes in the bodies of Monochamus saltuarius adults, we dissected 70 adults that had emerged from cut pine bolts set at two locations at the frontline of pine wilt disease spread in Nagano Prefecture, Japan. Fourth-stage dispersal juveniles of Bursaphelenchus nematodes were detected in 39 insects; PCR-based identification showed that the insects mainly harboured B. mucronatus, but could sometimes harbour B. xylophilus or both. Detailed dissection of 17 insects revealed that hundreds of Bursaphelenchus nematodes were often found in the reproductive organs of both sexes, including the inner parts such as the internal sac and the ejaculatory ducts in males. Thus, the residence of Bursaphelenchus nematodes in the reproductive organs of their vectors is not an accidental invasion but indicative of the phoretic nature of the nematodes.