Order Dorylaimida

                                       Rev 07/03/08

Classification:

Adenophorea

Enoplia

Dorylaimida Pearse, 1942

The first species in this group (Dorylaimus stagnalis) was described by Dujardin in 1845.  The order Dorylaimida was proposed by Pearse in 1942.

Key to the Order Dorylaimida (suborders, superfamilies, families and genera)

Classification and Characteristics Charts of the Orders Dorylaimida and Triplonchida

• Sub-orders
• Superfamilies
• Families
• Genera

Morphology and Anatomy:

• members of Dorylaimida have a movable mural tooth or hollow spear - odontostyle - which originates from a migrated stomal cell (from the Cheilostome); 
• spear extensions originate from an esophageal cell (the Esophostome); 
• have a two-part esophagus which is slender anteriorly and has a posterior swollen glandular and muscular region.
• have a smooth cuticle;
• in the plant-parasitic forms, the movable tooth is protrusible, usually hollow, and is termed the odontostyle. The odontostyle can be quite long, so that the nematode can feed through many layers of root cells. 
• the odontostyle is connected to the lining of the stoma by a cuticular membrane that becomes variously folded as the odontostyle is extended or retracted. The folds in the membrane refract light passing through the specimen and form a "guiding ring" around the odontostyle. 
• species of nematodes in most families in the Dorylaimida do not feed on higher plants; they feed on algae, fungi or other nematodes.
• Etymology: laimos = greek for throat, dory = spear; thus Dorylaimus = "spear in throat".

Additional Information:

Plant-parasitic nematodes in the Dorylaimida are ectoparasites.  They exhibit some adaptations to greater productivity in their energetics and influence on the host:
           1. Immobilize feeding site (root tip)
           2. Deeper tissue penetration
           3. Nurse cell modifications - increased cell surface increased metabolic activity
      Additionally, they are the group of nematodes that transmit plant viruses:  NEPO (nematode-transmitted polyhedral) viruses by the Longidoridae. Examples: tomato ringspot, grapevine fanleaf
      

Note: in 1995 DeCraemer moved the Trichodoridae to the Triplonchida on the basis of odontostyle and esophagus morphology and ultrastructure of the cuticle.

Not all Dorylaimida have a stylet (sometimes called spear to distinguish it from the stomatostyle of the Tylenchida) but have a tooth. In the few Dorylaimida specialized for plant parasitism,  the tooth is an odontostyle.  In some predatory Dorylaimida the tooth, positioned subventrally in the stoma, lacks a lumen.  When prey are punctured, food passes along the tooth into the stoma. In other Dorylaimida, including plant parasites and predators such as Labronema, the tooth is hollow and food passes through its lumen.  The lumen is formed by longitudinal infolding which is marked by a seam along its dorsal surface.  Where there is a spear extension or odontophore, it is a specialization of the cuticle-lined esophageal lumen.  The odontostyle and odontophore are protracted and retracted as one unit respectively by sets of eight and four muscles (Baldwin et al, 2004).

References

Baldwin, J.G., S.A. Nadler and B.J. Adams. 2004. Evolution of plant parasitism among nematodes. Ann. Rev. Phytopathol, 42:83-105.

Dujardin, F. 1845. Histoire Naturelle des Helminthes ou Vers Intestinaux.  Paris. 654p.

Jairajpuri, M.S. and W. Ahmad. 1992. Dorylaimida: free-living, predaceous and plant-parasitic nematodes. Brill, Leiden. 458 p.

Pearse, A.S. 1942. Introduction to Parasitology.  Baltimore. 357p.

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