Xiphinema americanum
Cobb, 1913
The American Dagger Nematode

Photo Galleries-

George Washington Memorial Parkway
Konza Prairie
Haughton Crater
Homestead Nat'l Monument

     2.0 mm; a = 52; b = 7.0; c = 54; V = 50
     2.0 mm; a = 58; b = 5.5; c = 55; T = 50

     Body spiral when relaxed, cylindroid except at extremities.  Lateral field 1/4 to1/3 body width, composed of a series of chain-like cells, each with  a distinct pore.  Lip region set off by slight depression, the papillae slightly elevated. Spear 80-90u long with 44-50u long extensions which are modified into elongate, flange-like expansions.  Guiding ring fragile, double.  Cuticle about the vestibule must be very strong for it functions as a spear guide without being sclerotized.  Basal portion of esophagus 21/2 to 3 times as long as neck width.  Cardia simple, conoid.  Intestinal cells packed with coarse, hyaline grannules. Prerectum length 4-6 times body width.  Rectum length near anal body diameter. Tail varying from bluntly conoid to dorsally convex-conoid, sometimes almost subacute.
     Males rather common in Great Plains populations but in no instance have they been observed fertilizing the associated females.  Many have normally developed testes producing spermatozoa while in others the testes are rudimentary.  Supplements 5-8, mammiform.  Spicula slightly arcuate.  Muscle bands 14-22.  Tail slightly arcuate, usually somewhat shorter than that of female.
     Habitat:  One of the most common nemas of the Great Plains.  Found about roots of all kinds of plants from native grass to cottonwood trees, feeding ectoparasitically with apparently no indication of choosing hosts.  Especially prevalent in windbreaks where decline and dieback are present.  Doubtless it is the primary parasite making openings through which fungi and bacteria enter to join in the destruction of root systems.  In severely infested trees it generally is almost impossible to find a single live feeder root.
     Xiphinema americanum is attacked by a bacterial parasite which enters  the body through the vulva, migrates through the gonads and completely destroys the ovaries.  It is not unusual  to find a specimen in which one ovary  has been destroyed while the other is producing eggs.  In the Great Plains area and other north central states the incidence of infested females usually ranges from 5-10%.  However, in Puerto Rico in the vicinity of the Agricultural Experimental Station near Rios Piedras, it is difficult to find X. americanum and almost every one is parasitized by the bacterium.  Under these humid, warm conditions the parasite gives an almost complete control.
     When processing soil for X. americanum use cold water and work rapidly, which will give  a recovery of 90-95% through the funnels.  But if the water is warm the nemas will go into shock, cease movement and only a small portion will be recovered.
     In the writer's opinion [Gerald Thorne], X. americanum causes more damage to crops, orchards and timber than any one species of nematode in the United States.

DNA Sequences Obtained
Specimen: Collected:
9Mile 4Core2-7 9 Mile Prairie
9Mile 4Core2-7a 9 Mile Prairie
Konza IIBB-57 Konza Prairie, First survey