Ultrastructure of Esophageal Gland Secretory Granules in Juveniles of Heterodera glycines.

Ultrastructural observations of the feeding sites of soybean cyst nematode juveniles 3 days after inoculation of soybean roots revealed the presence of feeding tubes in the host cell syncytium. Feeding tubes, which were extruded from the stylet tips, were formed by products of secretory granules that originated in the dorsal esophageal gland and accumulated in the ampulla of the gland extension. Granules traversing the space between the gland cell and the ampulla were regulated in their movement by two sets of sphincter-like muscles located anterior and posterior to the metacorpus pump chamber. Sections through the sphincter muscles revealed obliquely arranged fibers, which in a contracted mode caused microtubules in the gland extension to be tightly packed and devoid of granules.