Rev 09/26/07

Classification and Characteristics Charts of the Orders Dorylaimida and Triplonchida


Morphology and Anatomy:

Nematodes in the family Longidoridae are identified by the greatly elongated odontostyle (50-200 Ám long) plus the odontophore which may be plain or heavily flanged.

Loof and Coomans (1972) observed that the genera Longidorus and Paralongidorus on the one hand, and Xiphinema on the other, exhibit distinct differences with regard to location, shape, and size of the nucleus of the dorsal esophageal gland.  These and other observations support the subdivision of the Longidoridae into two subfamilies, Longidorinae and Xiphineminae.

  1. The genera Xiphinema and Longidorus appear on the basis of morphology to be very closely related.  These two genera are readily distinguished from other genera of the Dorylaimoidea.
  2. The species of Xiphinema and Longidorus are relatively large nematodes.
               1. Longidorus is 2 to 8 mm in length.
               2. Xiphinema is 2 to 5 mm in length.
  3. The species of Xiphinema and Longidorus are also characterized by the presence of a very long odontostyle.  The stylet and its extension are approximately 150 Ám or more in length.
    1. In Xiphinema, the guiding ring is located near the base of the odontostyle, just before its junction with the stylet extension (odontophore).  A flanged odontophore is characteristic of Xiphinema.
     2. In Longidorus, the guiding ring is located 2 lip region widths from the anterior end; no flanges occur on the posterior end of the odontophore.
  4. Both Xiphinema and Longidorus have a 2-part esophagus typical of most Dorylaimida, with a slender anterior part and swollen glandular and muscular posterior bulb.
  5. In Xiphinema and Longidorus, the cross-sectional configuration of the spear is cylindrical and the cross-section of the odontophore is tri-radiate as in the esophagus.  The esophagus has a tri-questrous lumen.
  6. Males of Xiphinema and Longidorus have paired pre-anal papillae and a ventromedian row of supplements.  The number and arrangement of these papillae are of importance in distinguishing species.  But, males are rare in most species.
    Males have paired spicules, but no gubernaculum; they have no bursa.
  7. Females of Xiphinema usually have two, but sometimes one, ovaries.  Females of Longidorus have 2 ovaries.  The ovaries, when both occur, are opposed and reflexed.

Molecular characerization, based on D2-D3 region of 28S and partial 18S rRNA genes resolves three Clades of species of Longidorus, Paralongidorus and Xiphinema.  Clade I is cmprised of Longidorus and Paralongidorus, Clade II of Xiphinema americanum and Xiphidorus, and Clade III of the non-americanum Xiphinema spp. (Palomares-Rius et al., 2013).


Decraemer, W, and Robbins, R.T. 2007.  The who, what and where of Longidoridae and Trichodoridae.  J. Nematology 39:295-297.

Lamberti, Taylor and Seinhorst, Nematode Vectors of Plant Viruses, New York: Plenum Press (1974), pp. 40-41.

Loof, P.A.A. and Coomans, A. 1972. The Oesophageal Gland Nuclei of Longidoridae (Dorylaimida). Nematologica 18:213-233.

Palomares-Rius, J.E., Cantalapiedra-Navarette, C., Gutierrez-Gutierrez, C., Liebanas, G., Castillo, P. 2013. Morphological and molecular characterisation of Paralongidorus plesioepikimis n.sp. (Nematoda: Longidoridae) from southerrn Spain. Nematology 15:363-378.

Robertson and Taylor, Nematode Ultrastructure. The Feeding Apparatus of Longidorus and Xiphinema, Scottish Horticultural Research Institute (1977), p. 3.


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