Plant-parasitic nematode feeding tubes and plugs: new perspectives on function

Abstract

Several structures associated with feeding by plant-parasitic nematodes have been described using two terms, feeding tubes and feeding plugs. However, both of these terms encompass multiple structures of independent evolution, some of which are functionally distinct. We have reviewed the literature on both structures and provide a new perspective on the function of intracellular feeding tubes to maintain the integrity and efficacy of the feeding site. We propose that they provide sufficient hydraulic resistance against the feeding site pressure to prevent it from collapsing during feeding. In addition, we propose that extracellular feeding tubes of migratory ectoparasites should be considered as the functional analogue of the stylet of all other plant-parasitic nematodes for withdrawal of host cell cytoplasm and, therefore, provide an example of convergent evolution. We also suggest that the main role of the feeding plug, irrespective of origin or composition, may be in adhesion.