1. Round Worms Belong to Phylum NEMATODA (Aschelminthes)

Unit 5 Review #4

1. Round worms belong to Phylum NEMATODA (Aschelminthes)

2. Most round worms are actually free-living, but we focused on the parasitic ones.

3. An acoelomate is an animal that does not possess any true body cavity. A coelomate is an animal that is completely lined by mesodermally-derived tissues. In contrast, a pseudocoloem is lined to the outside by mesoderm and a bit of ectoderm tissue and the inside is from endoderm. See below 4. Roundworms possess a PSEUDOCOELOM

5. The majority of roundworms are dioecious. Therefore they must find the opposite sex to complete sexual reproduction.

6. Complete guts have a mouth at one end an anus at the other. Incomplete guts use the mouth to take in food and expel wastes. The advantage is that a complete gut does not mix waste with food, it is much more efficient. Round worms use a complete gut, that is one of their advancements.

7. Both Annelids (segmented worms) and Nematodes (round worms) use bilateral symmetry. So did Platyhelminthes (flat worms)

8. Possessing a Coelom or even a Pseudocoelom provides the adavantage of creating space for separate organs to sit and work without interfering with other tissues and organs. Example, the circulatory system can work without interfering with movement in the digestive system.

9. See the picture below:

10. The most common parasitic round worm in Canada and U.S. is the "pinworm".

11. A) GUINEA worm

B) Filarial lymphosis causing Elephantiasis. C) Ascaris

D) Heartworm

E) Trichinella

F) River blindness roundworm- A filarial worm called "Onchocerciasis". 12. A) Hookworm

B) Ascaris

C) Pinworm

D) Elephantiasis – A type of filarial worm 12. Segmentation : Is the repetition of units that bear similar patterns of muscle and nervous structures as well as other organs. 13. Three classes of ANNELIDA include: POLYCHAETA, OLIGOCHAETA and HIRUDINEA.

14. Leaches belong to class Hirudinea, leaches posses a) Suckers, b) Anticoagulant and c) Anesthetic.

15. Marine worms belong to class POLYCHAETA. 16. Earthworms belong to class OLIGOCHAETA.

17. Earthworm digestive (MPECGI) tracts include: a) Pharynx for sucking in food and passing onto Esophagus. B) Crop which stores food temporarily C) Muscular Gizzard for grinding up food. D) Intestine for absorbing nutrients into blood stream.

18. Digestive Gland cells produce enzymes for digestion. 19. Peristalsis is a rhythmic contraction of circular and longitudinal muscles that pushes things along inside the digestive tract.

20. Earthworms posses a closed circulatory system, in larger animals this system delivers blood to tissues much faster and more efficiently than in an open circulatory system.

21. Setae are bristles that the worm can extend and retract, these bristles can help provide traction and can be used for anchoring it into its burrow. 22. Hemoglobin is the protein molecule that carries

O2 and makes blood red.

23. There are 5 pairs of hearts. So a total of 10 hearts.

24. The Belly surface is VENTRAL the rear region is POSTERIOR.

25. The Back surface is DORSAL and the front region is ANTERIOR.

26. Earthworms keep skin moist and protected with outer cuticle and mucous glands.

27. The simple brain is located just dorsal to the pharynx. 28. The brain branches off to form two circumpharyngeal nerves that go around the pharynx and then merge together to give rise to the ventral nerve cord.

29. Both motor nerves and sensory nerve attach onto the ventral nerve cord.

30. Hermaphrodites are individuals that posses both male and female reproductive organs.

31. Testes would be located in segment 10 and 11. They are responsible for Sperm production. 32. Ovaries are located in segment 13 and they produce eggs.

33. The clitellum is a swollen ring that contains a great number of mucous gland cells these secretions play an important role in mating and in protecting the developing embryos.

Evolutionary Advancements

1. Nematodes have a Pseudocoelom and their digestive tract is a complete gut. 2. Most Nematodes are dioecious (separate sexes) this ensures for better genetic diversity as they must find a mate for sexual reproduction.

3. Dioecious – Separate sexes. Monoecious – Hermaphrodites.

4. Annelids are more advance than nematodes in that they possess a True Coelom, a closed circulatory system and a much more advanced digestive tract.

5. In Nematodes a fluid filled pseudocoelom circulates oxygen and nutrients and picks up metabolic wastes. In Annelida blood circulates through hearts and blood vessels.

Disorders Caused by Parasitic Roundworms: 1. Guinea worms are transmitted through contaminated drinking water that contains infected copepods (small crustacean). The larvae hatch out and reach sexual maturity in the human intestine. The worms mate and the males die. Females then migrate from gut into body tissue and grow up to a meter in length just under the skin. Then they form an ulcer through the skin to release their fertilized eggs back into the water. 2. Filarial worms block lymphatic vessels. These larvae are transmitted through biting insects (especially mosquitoes). They then circulate around lymph vessels, they grow and reproduce sexually. As they grow they often block the lymph vessels (especially those vessels of the arms, legs, scrotum and breasts) causing enormous swelling and inflammation. Then a biting insect bites host to pick up microfilarial larvae and transmit to another host. 3. The main disorder associated with hookworms is PARASITIC ANEMIA. As hookworms anchor into gut they feed off of blood in the tissues leaving the host low on blood and more prone to other infections.

4.About 25 % of the world’s population are afflicted with hookworms. Juvenile hookworms developing in soil, then burrow into host through the skin. Then they circulate through the blood stream and reach the intestinal wall where they anchor and suck blood and tissue fluids. They reach maturity and sexually reproduce to release fertilized eggs into feces.

5 – Trichinella spirellis is a small (3-4 mm) roundworm that lives in the intestine of its host and causes little problem during this stage of its cycle. When they sexually reproduce the female holds the fertilized eggs in her body and then give birth to hatched larvae. These larvae burrow through the intestinal wall and get into the blood or lymph systems. They then burrow into organs and muscles causing excruciating pain/fevers etc. They then encyst themselves and lie dormant. When these tissues are consumed by another animal they hatch out and reach sexual maturity in the intestinal tract.