General CharacteristicsBilaterally symmetrical, triploblastic,

vermiform (worm-like) roundwormsUnsegmentedBody has more than 2 cell layersPseducoelmate (body cavity is a

pseudocoel)

General CharacteristicsBody 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 structuresSeparate sexes, usually sexual reproduction

General CharacteristicsNervous system with pharyngeal ring,

longitudinal nerve in epidermal cordHave 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 CharacteristicsMost have renette cells to conserve water;

some only have ductsUsually small – less than a millimeter longCan live almost anywhere, species can be

free-living or parasitic.Hydrostatic skeleton formed by pseudocoel

Classes

AdenophoreaTrichuris trichiura: whipwormTrichinella spiralisRomanomermis culicivoraxXiphinema index: Dagger nematode

http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromCD/0847/026B.GIF

http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromWWW/trichuris/ttrichmf.jpg

SecernenteaCaenorhabditis elegans

C. Elegans “The Worm”Enterobius vermicularis:

pinwormAncylostoma duodenale:

oldworld hookworm

http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromWWW/cele/b0523_5_vul.jpeg

http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/upenn/oxyurisf.jpg

http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromWWW/hook/hookfila.jpg

Body PlanBilaterally

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 continuedMuscles 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

FeedingNear 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.

RespirationBreathe by simple diffusion.

http://www.dkimages.com/discover/previews/740/48842.JPG

CirculationNo circulatory systemFoods circulate in pseudocoelem through

body movements

ExcretionHave 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.

Renette Cells

ResponseHave 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

ResponseAt 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.

ResponseThe 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.

MovementNematodes 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

ReproductionBasic 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 ovariesseminal receptaclesUteriovijector vuvla

ReproductionAll nematodes lay eggsSyngamy, or cross fertilization, is common in most

nematodes. Hermaphroditism can occurParthenogenesis 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 fertilizationDioecious

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/>