Submitted to: Journal of Helminthological Society of Washington
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 1997
Publication Date: N/A
Interpretive Summary: Plant-parasitic nematodes are microscopic worms that destroy plant roots and cause an eight-billion-dollar annual loss to U. S. agriculture. The lesion nematode is the third most important agriculturally damaging nematode, and it occurs in most locations of the U. S. New methodology for nematode control is needed because previously effective nematicides have been taken off the market due to their persistence and potential for ground-water contamination. In this investigation, ARS scientists and a collaborator from Germany have utilized the power of electron microscope to obtain new information on the structure of nematode glands that produce secretions that enter host cells, cause damage, and reduce the yield of a wide range of crop plants. The results may provide a better understanding of nematode-plant interactions that may lead to better control strategies. Therefore, the results will be used by ARS, university, and private sector scientists in developing new methods of controlling nematode damage.
Various stages of the lesion nematode Pratylenchus penetrans were observed using transmission electron microscopy (TEM) and low temperature scanning electron microscopy (LTSEM) to elucidate structural anatomy of the esophagus, intestine and reproduction system. In cross sections, the wall of the esophagus is circular through the procorpus and triradiate in the metacorpus where it is extendable as part of the metacorpus pump valve. A pair of esophageal lumen branches terminates as quadriradiate valves in subventral gland ampullae. The central lumen then extends posteriad to become part of the esophago-intestinal valve. The enlarged intestinal lumen is delineated by scattered evaginated membranes of the epithelial cells. The lumen may be occluded during non-feeding periods or when the intestine becomes compressed by the reproductive organs. Testes containing spermatocytes with membrane bound nuclei transform into amoeboid spermatids with electron opaque, non-membrane bound nuclei that are surrounded by fibrous bodies. Spermatozoa having irregular clumps of non-membrane bound chromatin and surrounding mitochondria as well as residual fibrous bodies were found in seminal vesicles and vas deferens of males and in spermathecae of female gonads. The ultrastructure of the male and female reproductive organs is compared to similar features observed with light microscopy and LTSEM.