Nematoda

General Characteristics Bilaterally symmetrical, triploblastic, vermiform (worm-like) roundworms Unsegmented Body has more than 2 cell layers Pseducoelmate (body cavity is a pseudocoel)

General Characteristics Body is round in cross section and covered with a thick cuticle that is periodically shed as the worm grows Muscles are along the length of body not encircling it. Have no circulatory or respiratory structures Separate sexes, usually sexual reproduction

General Characteristics Nervous system with pharyngeal ring, longitudinal nerve in epidermal cord Have unique cephalic sense organs (amphids), only some have lateral, caudal sense organs (phasmids) Tubular digestive system that passes from mouth to anus, one way. Intestines specialized and complete

General Characteristics Most have renette cells to conserve water; some only have ducts Usually small – less than a millimeter long Can live almost anywhere, species can be free-living or parasitic. Hydrostatic skeleton formed by pseudocoel

Classes Nematoda Adenophorea Secernentea

Adenophorea Trichuris trichiura: whipworm Trichinella spiralis Romanomermis culicivorax Xiphinema index: Dagger nematode http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromWWW/trichuris/ttrichmf.jpg http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromCD/0847/026B.GIF

Secernentea Caenorhabditis elegans C. Elegans “The Worm” Enterobius vermicularis: pinworm Ancylostoma duodenale: oldworld hookworm http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromWWW/cele/b0523_5_vul.jpeg http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromWWW/hook/hookfila.jpg http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/upenn/oxyurisf.jpg

Body Plan Bilaterally symmetrical, unsegmented worms. They are covered with a flexible and thick cuticle, that is shed as the worm grows. http://www.kent.k12.wa.us/staff/neilcochran/APBioDocuments/ch26_lecture.ppt#306,54,Phylum Nematoda: Roundworms

Body Plan continued Muscles under the epidermis extend the length of the body rather than encircling the body. They have a hydrostatic skeleton. They have a pseudocoel which separates the endoderm-lined gut from the rest of the body.

http://plpnemweb.ucdavis.edu/nemaplex/images/metazo12.jpg

Feeding Near mouth there are usually 16 hair-like sensory organs. The mouth is often equipped with piercing organs called stylets - sharp spikes used to kill cells or move through the dirt http://www.cpes.peachnet.edu/nemabc/_borders/Pred._dorylaimid.jpg

Feeding continued. Food passes through the mouth as a result of the sucking action of a muscle chamber called the pharynx. Food then goes directly to the digestive tract, where it broken down and nutrients are absorbed. Digestive tract connects directly to the anus. Many nematodes are parasites.

Respiration Breathe by simple diffusion. http://www.dkimages.com/discover/previews/740/48842.JPG

Circulation No circulatory system Foods circulate in pseudocoelem through body movements

Excretion Renette Cells Have excretory ducts that permit them to conserve H20 and live on land Unique excretory system of collecting tubules or renette cells (excretory glands) Nitrogenous waste is excreted in the form of ammonia through the body wall Excretory system, if present, empties through an anterior, ventromedial porus.

Response Have a nervous system with pharyngeal nerve ring Unique cephalic sense organs, amphids Some with caudal sense organs, known as phasmids The muscles are activated by two nerves that run the length of the nematode on both the dorsal (back) and ventral (belly) side

Response At the anterior end of the animal, the nerves branch from a dense circular nerve ring surrounding the pharynx, and serving as the brain. Smaller nerves run forward from the ring to supply the sensory organs of the head.

Response The body of nematodes is covered in numerous sensory bristles and papillae that together provide a sense of touch. Behind the sensory bristles on the head lie two small pits, or amphids.

Movement Nematodes move by undulations or wave-like motions of the body. The muscles are able to “manipulate” each other to contract/relax accordingly

Movement cont. There are the four "fields" of longitudinal muscles. Because the pseudocoelomic fluid is incompressible, the internal pressure increases causing stretching of muscle cells in another part of the body.

Movement cont. Through this system of local contractions of the muscle fields the dorsal and ventral longitudinal musculature act as antagonists, producing sinusoidal waves along the length of the nematode's body. Most nematodes lie on their sides and the resulting dorsi-ventral undulations move the nematode in the horizontal plane through an aquatic medium

Reproduction Basic male reproductive structures include: One Seminal vesicle - sperm accumulate here Vas deferens opening into a cloaca Bursae - thin cuticle extensions Spicules

Basic Female reproductive structures: one or two ovaries seminal receptacles Uteri ovijector vuvla

Reproduction All nematodes lay eggs Syngamy, or cross fertilization, is common in most nematodes. Hermaphroditism can occur Parthenogenesis is also a normal means of reproduction in some nematodes.   Unique to animal kingdom, nematodes produce ameboid sperm - allows sperm to crawl to ova against hydrostatic pressure Internal fertilization Dioecious

Works Cited Lower Metazoan Phyla. Nemaplex, University of California Davis. 15 April 2010 <http://plpnemweb.ucdavis.edu/nemaplex/Kingdoms/metazoa.htm#Nematoda> Waggoner, Ben and B.R. Speer. Introduction to Nematoda. UCMP. 15 April 2010 <http://www.ucmp.berkeley.edu/phyla/ecdysozoa/nematoda.html> Mehaffey, Leathem. Phylum Nematoda. Biology 266, Vassar University. 15 April 2010 <http://faculty.vassar.edu/mehaffey/academic/animalstructure/outlines/nematoda.html> Phylum Nemata. Biology of Parasitism – Lecture Notes, University of California Davis. 15 April 2010 <http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/E156charac> Raven, Robert H. and George B. Johnson. Biology. New York, NY: McGraw Hill, 2002. Ramel, Gordon. Phylum Nematoda. Earthlife Web. 15 April 2010 <http://www.earthlife.net/inverts/nematoda.html> Nematology Lab at UNL. University of Nebraska – Lincoln. 20 April 2010 <http://nematode.unl.edu/>