Observations On the Ultrastructure and Function of the Dorsal Oesophageal Gland Cell in Xiphinema Index

Abstract

In Xiphinema index the dorsal gland cell extends along the length of the basal oesophageal bulb on the dorsal side and the anterior half of the ventral side. The cell has a system of six ducts formed by deep infolds of the limiting cell membrane. Two ducts extend almost the entire length of the bulb on the dorsal side and four extend half-way on the ventral side. The ducts join anterior to the gland nucleus to form a transverse, fan-shaped main duct. Folds in the lining of the ducts facilitate dilation and depletion of the duct system seen in feeding nematodes. Electron-dense granules, closely associated with dictyosomes were aggregated near the ducts in nematodes which had been ingesting food, but only a small amount of electron-dense material was found at the apices of the folds in the duct lining and an electron-dense plug was observed where the main duct opens into the food canal. This orifice is a longitudinal slit opened by four radial dilator muscles just anterior to the pump chamber. Three other groups of radial muscles attach to the ventral and lateral sides of the food canal to balance the pull of the dilator muscles. Observations with the light microscope on nematodes which were feeding suggested that the part of the main duct near the food canal, which is lined with a thin layer of cuticle, may act as a one-way valve whilst the slit is dilated.