Changes in surface features during desiccation of the anhydrobiotic plant parasitic nematode Ditylenchus dipsaci.

The anhydrobiotic nematode Ditylenchus dipsaci is a fast-dehydration strategist, itself generating the slow rate of water loss necessary for survival. A permeability slump occurs during the initial phases of desiccation. This may be produced by changes in the nematode's cuticle. Two scanning electron microscopic techniques were used to follow changes in surface structures during desiccation. Freeze substitution and critical-point drying produced artifacts that obscured changes produced by the desiccation of the nematode. Low-temperature field emission scanning electron microscopy (FESEM) was successful in following changes that reflected those observed by light microscopy (LM). Significant changes in diameter, the lateral alae, and the cuticular annulations were demonstrated using this technique. Two types of annulations were observed: the major annulations, which extended to meet the margins of the lateral alae, and the minor annulations, which did not. With desiccation the prominence of the annulations increased, their spacing decreased, and the minor annulations extended closer to the margins of the lateral alae. These observations are consistent with the permeability slump resulting from a decrease in the width of the annulation groove and an increase in its depth. However, this requires confirmation using techniques that can follow annulation changes in individual nematodes.