Order: Triplonchida Cobb, 1919
The cuticle in the family Trichodoridae, which contains plant-feeding nematodes, differs from that in other Enoplea. It has has six layers, the innermost layer consisting of three multilaminate units. The cuticle ultrastructure was the basis for moving the family Trichodoridae from Dorylaimida to Triplonchida by Siddiqi (1983) (Mountport et al, 1987)
Classification and Characteristics Charts of the Orders Dorylaimida and Triplonchida
Plant-parasitic nematodes in the Triplonchida are
ectoparasites. They exhibit some adaptations to greater
productivity in their energetics and influence on the host:
1. Immobilize feeding site (root tip)
2. Nurse cell modifications - increased cell surface, increased metabolic activity, e.g. Paratrichodorus.
Additionally, they are the group of nematodes that transmit plant viruses:
TOBRA (tobacco rattle) viruses by the Trichodoridae [formerly called NETU (nematode-transmitted tubular) viruses]. Examples: pea early browning, tobacco rattle virus.
The feeding apparatus of some Triplonchida is an open stoma characteristic of microbivores; in others it is a stoma lined with complex sets of cuticular plates of uncertain function, as in Diphtherophora; and in others an onchiostyle for plant feeding, as in Trichodorus. The curved onchiostyle is a modified solid dorsal tooth that extends from the wall of the anterior end of the esophagus. It lacks a lumen but may have a dorsal groove; food passes from the puncture directly into the stoma that surrounds the stylet. (Baldwin et al, 2004).
Baldwin, J.G., S.A. Nadler and B.J. Adams. 2004. Evolution of plant parasitism among nematodes. Ann. Rev. Phytopathol, 42:83-105.
Mounport, D.; Baujard, P.; Martiny, B. 1997. TEM observations on the body cuticle of Trichodoridae Thorne, 1935 (Nematoda: Dorylaimia). Nematologica 43:253-258.
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