Nematodes (Roundworms)

{ Characteristics }

Roundworms are unsegmented worms that have pseudocoeloms - a false coelom - and digestive systems with two openings - a mount and an anus.

Reproduction

Roundworms have only one means of reproducing - sexually.

Roundworms reproduce using internal fertilization. Most species are not hermaphroditic, so usually the male inserts sperm inside the females reproductive tract.

Examples of Roundworms

Roundworms are free-living, but hey are better known as parasitic. They include trichinosis-causing worms, filarial worm, ascarid worm, and hookworms. Trichinosis is caused by the Trichinella roundworm. It completes its lifecycle only when an animal eats muscle containing the cysts - inactive larva. Filarial worms cause elephantiasis, a condition where the infected part of the body swells enormously. The filarial worms block the passage of fluids within lymph vessels in the infected area. Acarid worms - such as Ascaris lumbricoides - cause malnutrition in more than 1 billion people worldwide. Hookworms suck their host’s blood, causing weakness and poor growth.

Vocabulary

pseudocoelom - false coelom

anus - the posterior end of the digestive tract

Works Cited

http://www.ah.novartis.com/images/cab/dog_Tclifecycle.jpg

http://www.microbeworld.org/images/stories/twip/trichinella_spiralis.jpg

http://www.bio.davidson.edu/courses/immunology/Students/spring2006/Heeren/eleph.html

http://www.histopathology-india.net/roundworm.JPG

http://www.metapathogen.com/IMG/ascaris-life-cycle.png

http://news.bbc.co.uk/2/hi/health/7856095.stm