Formation of the odontostyle during molting of the nematode Xiphinema americanum (Nematoda: Dorylaimoidea)

A light and transmission electron microscope study was made of the feeding apparatus of the nematode Xiphinema americanum Cobb, 1913, during molting. The odontostyle, the anterior part of the feeding stylet, is formed by two cells in the slender esophagus, one located posterior to the other. A deep cylindrical invagination develops into the posterior (odontostyle) cell, while the anterior cell extends a tubular sheath around the invagination and forming odontostyle. The odontostyle cell produces a shorter forward-projecting sleeve inside and sealed to the sheath by a junctional complex. Dense granules produced from Golgi complexes in the odontostyle cell are exocytosed into the extracellular pocket thus formed. Granules coalesce in this mold to form the extracellular odontostyle. The invagination and sheath deepen posteriorly as formation proceeds, reaching down to the looped esophagus as the odontostyle nears completion. During the posterior shift to the storage site, the odontostyle contracts and becomes electron lucid. In the following intermolt storage period, it remains extracellular, surrounded by the odontostyle cell. It is suggested that changes in shape of the anterior and odontostyle cells, and movement of these cells are largely responsible for movement of the odontostyle in the esophagus.