Ferris, Howard Department of Nematology, University of California, Davis, California.
- Links to Primary Literature
- Additional Readings
An order of nematodes (roundworms) formerly constituting at least two important groups of animal parasites: the mermithids, which are parasites of invertebrates, and the trichinellids, which are parasites of vertebrates. These nematodes are characterized by a pharynx that is narrow and thin-walled anteriorly and is surrounded posteriorly by unicellular, glandular stichocytes, each with a duct into the pharyngeal lumen (Figs. 1 and 2). The pharynx extends one-fourth to nine-tenths of the body length in various taxa and is almost devoid of musculature. The region of the pharynx surrounded by stichocytes is known as the stichosome. Recent phylogenetic analysis based on a synthesis of molecular and morphological data suggests that the stichosome may be an example of parallel evolution and that the trichinellids and mermithids are more appropriately separated as two orders: Trichinellida, with at least six families, and Mermithida, with two families. However, debate on the higher classification of nematodes continues, and opinion will no doubt refocus as new data emerge and are applied. See also: Medical parasitology; Nemata (nematoda)
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Its dedicated editorial team is led by Sagan Award winner John Rennie. Contributors include more than 9000 highly qualified scientists and 42 Nobel Prize winners.
MORE THAN 8500 articles and Research Reviews covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 17,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information