On the Formation and Ultrastructure of Feeding Tubes Produced By Trichodorid Nematodes

Abstract

Cine-film analysis, light and electron microscopy showed that the feeding tubes produced by feeding trichodorid nematodes (Trichodorus similis being the species most observed) appear to be initiated within the pharyngeal lumen of the nematode. The region concerned is that part of the cuticular lining that is supported by three 'strengthening rods' embedded in it. At a feeding site, just before the onchiostyle is first protracted for plant cell wall perforation, the anterior end of the strengthened region is closely applied to the wall. As onchiostyle thrusting continues, a secretion from the nematode is released that hardens between the onchiostyle and the lumen lining, forming a tube composed of electron-dense material. With further thrusting, after cell wall perforation, the tube extends in a thin layer through the perforation hole into the cell interior, where it is anchored by a small plug of hardened secretions which forms just inside the cell wall around the perforation. When as sometimes happens parasitized, dead and empty epidermal cells are punctured again, the onchiostyle is usually thrust deeper and deeper into such cells until it may reach and even perforate the wall of underlying cells. The nematode secretions then harden around the onchiostyle into a growing tube that may extend right into the underlying cells.