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NEMATODES

NEMATODES. ROUNDWORMS. What is a nematode?. A nematode is a roundworm. There are more nematodes are earth than any other multicellular animal. If you wiped out all of the people on earth, you could still see where the populations were concentrated if you looked at the number of nematodes.

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NEMATODES

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  1. NEMATODES ROUNDWORMS

  2. What is a nematode? • A nematode is a roundworm. • There are more nematodes are earth than any other multicellular animal. • If you wiped out all of the people on earth, you could still see where the populations were concentrated if you looked at the number of nematodes. • A handful of dirt may contain thousands. • They inhabit every ecosystem. • Some are free living and some are parasitic.

  3. They are colorless, unsegmented and lack appendages. Bilateral symmetry Separate sexes

  4. They may be a few millimeters or over a meter. • They are covered with a protective cuticle.

  5. Digestive system • They have a system described as a tube within a tube. What does that mean? • They have a mouth and an anus. • Food enters through a mouth which may have teeth. • Food goes into a muscular pharynx. This is where enzymes are made and digestion begins. • The pharynx is directly connected to the intestine (no stomach). • Digestion is completed and leftovers go through the rectum and out the anus.

  6. Parasitic roundworms • But, many roundworms are parasitic. They can infect plants, animals and humans. • Hookworms live in animals and humans. They feed on blood and can be a cause of anemia. (Most anemia is caused by lack of iron.) • Eggs develop in the intestines and pass out with the feces. • The eggs hatch into larva in the grass

  7. The larva bore in through the skin. Do you do anything that may make you vulnerable to a hookworm infection? • The larva migrate to the lungs. They are coughed up and then swallowed into the digestive system. • They mature in the digestive system and live in the intestines where they live off of blood. • Over a billion people in the world are infected.

  8. Monsters Inside Me- Flesh-Eating Hookworm – YouTube • Embarrassing Bodies | Hookworm | Channel 4 - YouTube

  9. Trichinella • Infect many mammals including people. • As larva, they live in the host’s intestine. • They then travel to the muscles where they form cysts. • If you eat meat that is undercooked and has the cysts, you get a disease called trichinosis. This usually comes from eating undercooked pork.

  10. trichinosis rap - YouTube

  11. Pinworms • Most common parasitic roundworm in the U.S. • Affects mostly children. • Does not cause serious effects. • The females move out of the intestine and lay their eggs around the opening of the anus. This causes itching. If scratched, the eggs can be spread to anything and anyone touched. • They live in the intestines and suck up blood so they also cause anemia.

  12. Ascaris • Live in intestines and absorb food. • Large parasite. May block intestines or lungs. • Follow the same path as hookworms. • The eggs (a female can lay 200 000 a day) pass out with feces . They survive in the soil or on plants until a host (person, horse, pig) comes into contact with them.

  13. Filaria • Mostly in tropics • Live in the lymphatic system. This is part of the circulatory system. It collects fluid and helps fight disease. • Cause elephantiasis • Worm is carried by insects

  14. Heartworm Mosquitoes carry the larva. They pick it up when they bite an infected dog. Can cause death when it attacks the heart.

  15. Loa loa worm

  16. Guinea worm • Most common in Africa • People get it from infested water.

  17. Excretory system • No specific organs. Wastes collect in a tube and go out a pore. • Marine species have renette glands to regulate the amount of salt.

  18. Muscular system • Nematodes have muscles that run the length of the body. This causes their whiplike back and forth movement.

  19. Respiratory system • No structures. Rely on diffusion. Must stay moist for diffusion to occur.

  20. Nervous system • They have an anterior nerve ring that goes around the pharynx. It serves as their brain. From this come 4 longitudinal nerves • They have sensory bristles for touch. They also have chemical receptors. • They have some neuroendocrine secretions. Your endocrine system is the system that is involved in secretion of hormones. Theirs controls molting, growth, cuticle formation and metamorphosis.

  21. Reproduction • Remember that sexes are separate. Males are smaller. • Females have ovaries, oviducts, uterus and vagina. Those connect to the outside at the genital pore. • Males have a testis, vas deferens, seminal vesicle and a bursa to transmit the sperm. • Fertilization is internal. • Eggs produced range from several hundred to thousands.

  22. Free living roundworms • Eat algae, fungi, small animals, fecal matter, dead organisms, and living tissue. • They help with decomposition and recycling of nutrients. • One roundworm, C. elegans was the the first multicellular animal to have its genome sequenced. They have 6 pairs of chromosomes and 20 000 genes.

  23. Good/Bad • Obviously parasites are considered harmful in both plants and animals. • However, nematodes have been used in genetic research. • They help with decomposition. • They help control bad insects. • They may help people fight allergies.

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