Ultrastructure of the attachment and feeding sites of Gracilacus latescens Raski, 1976 in timber bamboo roots and selected anatomical details of the female stylet

摘要

Mature female Gracilacus latescens are sedentary and remain attached by the stylet to the surface of timber bamboo roots (Phyllostachys bambusoides) for their entire life. Observations by transmission electron microscopy (TEM) of the anatomy of the anterior portion of the female body showed the stylet shaft surrounded by a thick stomatal wall sensu Endo (1983) and by large protractor muscles. Cross sections of the root at the site of nematode attachment showed accumulation of electron-opaque material between the nematode body and the epidermal wall penetrated by the stylet. Electron-dense material enwrapped the stylet from the point of its insertion in an epidermal cell wall until its end in the lumen of a sclerenchymal or cortical cell. Two to three cells are penetrated by the stylet. The electron-dense material appeared to originate from the walls of epidermal, cortical parenchymal and sclerenchymal cells perforated by the stylet. The thickness of this material increased with the number of sclerenchyma cell walls penetrated by the stylet. Cross sections of the enwrapped stylet showed it tightly encased in the electron-dense material, which appeared to anchor the stylet and consequently the nematode body to the root surface. A syncytium originates from the innermost cell reached by the enwrapped stylet and expands into the inner cortex and stele. Cell wall dissolution and pit fields are characteristics of the syncytium.