Submitted to: Journal of Helminthological Society of Washington
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/1998
Publication Date: N/A
Citation: Interpretive Summary: Plant-parasitic nematodes are microscopic soil worms that annually cause billions of dollars in crop losses in the United States. In particular, the lesion nematode consistently causes economic crop damage and has worldwide distribution. Its economic impact results not only from direct plant destruction but also from its association with many soil borne microorganisms, resulting in root lesions. One problem with developing safe, biologically based alternatives to the chemical nematicides that sometimes contaminate groundwater is that little is known about the biology of this nematode. The current study, which emphasizes the structure of the female gonad, provides new information on the structure of the reproductive system of this nematode. This information, which will be used by scientists developing methods of restricting the natural reproduction of nematodes, will eventually benefit the public when the resulting technology provides an alternative to chemical nematicides.
Technical Abstract: Transmission electron microscopy of the gonad of adult females of Pratylenchus penetrans revealed details of oocyte development and transformation of oocytes into eggs. Oogonial cell divisions were not observed; however, oogonial development into oocytes was distinctive in that most of the nuclei of ovarian cells were in the pachytene stage, i.e. prophase I of meiosis. In the mid section of the ovary, the oocytes increase in number, enlarge and accumulate in a single row. Next the oocytes enter a muscular oviduct and begin to synthesize and accumulate lipid bodies and protein granules. The plasma membrane becomes plicated and forms cisternae; centralized membrane junctions establish openings for oocytes to enter the spermatheca. After the spermatozoa penetrate the spermatheca, each oocyte traverses between columnar cells containing secretory granules, which appear to contribute to the vitelline layer of the egg. The posteriad region of the columnar cells merges with tissues to form the central lumen of the uterus that extends beyond the vaginal opening and into the postvulvar uterine branch of the ovary. The fertilized egg is deposited to the exterior after passing between cuticular vaginal and vulval walls supported by anteriad and posteriad muscle bands, having ventro-sublateral insertions on the body wall.