Nematoda

Author: Kirsty McGhie
**__EXAMPLES:__** //Ascaris lumbricoides "//Round Worm": it is responsible for the disease ascariasis in humans, and it is the largest and most common parasitic worm in humans. A quarter of the human population is estimated to be infected by this nematoda. //Ancylostoma duodenale "//Old World hookworm": lives in the small intestine of host such as humans, cats and dogs

__ HABITAT: __ Nematodes have adapted to almost every type of ecosystem including: marine, freshwater, polar regions, tropics, high and low elevations. They can be found in mountains, deserts, and oceanic trenches. They represent 90% of all life on the seafloor of the Earth.

__TYPE OF COELOM__: Pseudocoelom. Pseudocoelom are body cavities, this means that the nematodes have have what is called a "tube-within-a-tube" body plan. The secondary body cavity lies between the two tubes. The outer tube (also called the body wall or the **somatic** tube) typically contains the sense organs and muscles.

__ENDOSKELETON or EXOSKELETON__**:** None, nematodes do not have skeletons.

__TYPE OF NERVOUS SYSTEM__: Nematodes have circular brains as well as many longitudinal nerve cords.

__FEEDER__ **:** The nematodes work to find a host. Once one is found, the nematodes penetrate into the body cavity, usually via natural body openings. When they are in the body cavity, a bacterium is released from the nematode gut, which multiplies rapidly and causes rapid insect death. The nematodes then feed upon the bacteria and liquefying host.

__SYMMETRY__ **:** Bilaterally symmetrical, if a nematode were to be disected down the middle, the right side and left side would by symmetrical.

__REPRODUCTION__ **:** All nematodes lay eggs. Syngamy, or cross fertilization, is common in most nematodes. Hermaphroditism also occurs, with the nematode gonads producing spermatozoa first and storing them until the eggs are produced. Parthenogenesis is also a normal means of reproduction in some nematodes.

__CIRCULATORY SYSTEM__ **:** Nematodes do not have a circulatory system, they do not have blood.

__ENDOTHERMIC or EXOTHERMIC__ **.** Nematodes are neither endothermic or exothermic because no circulatory system.

__SEGMENTATION__ **:** Nematodes are unsegmented, meaning their bodies are one part, they are not made up of different segments.

__WORKS CITED__**: "Ancylostoma duodenale ." //Plpnemweb//. Web. 29 Mar 2011. [].

"Ascaris lumbricoides." //Wikipedia//. Web. 29 Mar 2011. .

Ramel, Gordon. "The Phylum Nematoda." Earth Life. N.p., n.d. Web. 27 Mar 2011. [].

Shapiro-Ilan, David, and Randy Gaugler. "Nematodes." Cornell University College of Agriculture and Life Sciences. Cornell University, n.d. Web. 27 Mar 2011. [].

"What are Nematodes?" University of Nebraska-Lincoln Nematology. N.p., n.d. Web. 28 Mar 2011. []. Yeh, Jennifer. "Body Cavities." //Novel Guide//. Macmillan Reference USA, n.d. Web. 27 Mar 2011. .