1. Nematoda

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

3. 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

4. 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

5. 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

6. Classes
Nematoda
Adenophorea
Secernentea

7. Adenophorea Trichuris trichiura: whipworm Trichinella spiralis
Romanomermis culicivorax
Xiphinema index: Dagger nematode

8. Secernentea Caenorhabditis elegans C. Elegans “The Worm”
Enterobius vermicularis: pinworm
Ancylostoma duodenale: oldworld hookworm

9. Body Plan Bilaterally symmetrical, unsegmented worms.
They are covered with a flexible and thick cuticle, that is shed as the worm grows.
Nematoda: Roundworms

10. 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.

12. 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

13. 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.

14. Respiration Breathe by simple diffusion.

15. Circulation No circulatory system
Foods circulate in pseudocoelem through body movements

16. 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.

17. 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

18. 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.

19. 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.

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

21. 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.

22. 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

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

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

25. 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

26. Works Cited
Lower Metazoan Phyla. Nemaplex, University of California Davis. 15 April 2010 <
Waggoner, Ben and B.R. Speer. Introduction to Nematoda. UCMP. 15 April 2010 <
Mehaffey, Leathem. Phylum Nematoda. Biology 266, Vassar University. 15 April 2010 <
Phylum Nemata. Biology of Parasitism – Lecture Notes, University of California Davis. 15 April 2010 <
Raven, Robert H. and George B. Johnson. Biology. New York, NY: McGraw Hill, 2002.
Ramel, Gordon. Phylum Nematoda. Earthlife Web. 15 April <
Nematology Lab at UNL. University of Nebraska – Lincoln. 20 April 2010 <