Ultrastructural Differences between the Propagative and Dispersal Forms in Pine Wood Nematode, Bursaphelenchus lignicolus, with Reference to the Survival

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Abstract
The ultrastructure of cuticle and intestine was compared between the dispersal and propagative forms of Bursaphelenchus lignicolus. With growth of the propagative form, the thickness of cuticle increased gradually, while the ratio of cuticle to body diameter decreased. The cuticle of dispersal 3rd-stage larvae (LXIIIs) was the thickest of all stages in the two forms. In the dispersal 4th-stage larvae (LXIVs), the ratio of basal layer was the largest (67% of cuticle). The external cortical layer was thicker in the dispersal form than in the propagative one. The large electron-lucent lipid droplets deposited deeply in the intestinal and hypodermal cells of LXIIIs. These lipid droplets were partly mobilized to glycogen granules with a development of LXIIIs to LXIVs.