Neutral Storage Lipid and Exit Behavior of Bursaphelenchus xylophilus Fourth- stage Dispersal Juveniles from their Beetle Vectors

The J4 dispersal juvenile is a specialized life stage of the pinewood nematode, Bursaphelenchus xylophilus (Steiner &Buhrer) Nickle, that is transported by cerambycid beeries in the genus Monochamus. The nlediafion of J4 exit fronl beetle vectors is poorly understood. We hypothesized that decreasing neutral storage lipid in B. xylophilus J4 was related to behaviors leading to their exit from the beetle on which they are carried. J4 remaining within beetles and J4 exited from beetles were fixed, stained, and digitized for computerized image analysis of neutral storage lipid content. Nematodes remaining within beetles had significantly higher neutral lipid area than those that exited during the first 4 weeks of adult beetle life. Neutral storage lipid content of J4 from within beeries decreased dramatically at week 5 and remained low through week 10. Desiccation was thought to be the reason for this decrease. Neutral storage lipid was correlated with nematode exit and may contribute to B. xylophilus exit from vectors.