Submitted to: Dekker Encyclopedia of Plant and Crop Science
Publication Type: Book / Chapter
Publication Acceptance Date: June 25, 2002
Publication Date: May 1, 2004
Citation: Lewis, S. A., Chitwood, D. J., McGawley, E. C. 2004. Nematode biology, morphology, and physiology. In: Goodman, R. M., editor. Encyclopedia of Plant and Crop Science. New York, NY: Decker. p. 781-783.
Interpretive Summary: Plant-parasitic nematodes are microscopic worms that attack plant roots and cause annual agricultural losses of nearly ten billion dollars in the United States. Probably the major problem associated with controlling nematode damage is that the few chemicals available for this purpose are far from perfect with respect to environmental safety, mammalian toxicity, or expense. Therefore, many scientists are attempting to develop new control methods based on nematode biology, morphology or physiology. This publication is a general review of these subjects. Areas of emphasis include the discovery of plant-parasitic nematodes shortly after the invention of the microscope, the reproductive systems of nematodes, and the ability of nematodes to survive environmental extremes and successfully find and infect host plants. The information contained in this review will be used by scientists developing safe and selective methods for controlling gplant-parasitic nematodes. The review will also be used by students and other members of the general public interested in learning the basic fundamentals of nematology.
Nematodes are a remarkably successful group of worm-shaped invertebrates adapted to survival in most ecological niches. The oldest writings describing nematode diseases of humans are from China and date from 4700 years ago. The invention of the microscope resulted in the discovery of the wheat seed gall nematode and other major plant-parasitic nematodes in Europe. Plant-parasitic nematodes exhibit a simple, direct life cycle tha usually includes egg, four juvenile, and adult stages. Many species are parthenogenetic; i.e., males and spermatozoa are not required for reproduction. The stylet is the most distinctive anatomical feature in phytoparasitic nematodes; stylet shape can often be used to determine the nematode genus. Nerve cells in the nematode are grouped into ganglia, which in turn are grouped into a circumesophageal commissure or collection of coordinated nerve cell bodies that become the primitive nematode brain. The physiological and biochemical control of nematode molting has not yet been elucidated, unlike the molting process in insects. Many nematodes can survive extended periods of drought or temperature stress via morphological and biochemical adaptations, such as the accumulation of the sugar trehalose and other specific molecules. The free-living nematode species Caenorhabditis elegans was the first multicellular animal to have its genome completely sequenced.