Study of the departure of pine wood nematode, Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae) from Monochamus alternatus (Coleoptera: Cerambycidae)

In order to study the causes of pine wood nematode (PWN) departure from Monochamus alternatus, the effects of the feeding behavior of M. alternatus on the start date of the departure of PWN were studied. The start date of the departure of PWN carried by the directly fed M. alternatus was 5-13 d after beetle emergence, mainly concentrated within 6-10 d, with a mean (+/- SD) of 8.02 +/- 1.96 d. The start date of the departure of PWN carried by the M. alternatus fed after starvation was 5-14 d after beetle emergence, mainly concentrated within 6-9 d, with a mean of 7.76 +/- 2.28 d. The results show that there was no significant difference in the start departure date of PWN between the two treatments. This shows that the feeding behavior of M. alternatus is not the trigger for PWN departure. At the same time, it was found that the motility of the PWN carried by M. alternatus at 8 d after emergence was significantly greater than that of the PWN carried by the newly emerged M. alternatus. And the PWN carried by M. alternatus at 8 d after emergence was extracted more easily than the PWN carried by newly emerged beetles. These results show that greater motility was associated with easier departure of PWN from M. alternatus. In addition, transcriptome sequencing found that the level of oxidative phosphorylation metabolism of PWN carried by beetles at 8 d after emergence was significantly higher than that in the PWN carried by newly emerged beetle. High oxidative phosphorylation was associated with increased energy production and motility by the PWN and were the internal cause of the start of nematode departure.