1. Roundworms Ch. 27.2

2. Phylum – NEMATODA Among the most numerous animals

3. What is a Roundworm?  Slender and UNSEGMENTED; have tapering ends  Can be microscopic to a meter in length  Free-living in soil, sediments, water  High and low temperatures  Some are parasitic

4.  Develop 3 embryonic germ layers  Have a body cavity between endo and meso derms  PSEUDOCOELOM  ‘false coelem’

5.  Have a digestive tract with 2 openings  ‘tube within a tube’  Food moves in ONE direction  Excretion through the anus

6. Form and Function in Roundworms  Specialized tissues and organ systems that carry out body functions  More complex than PLATYHELMINTHES

7. Feeding  Carnivores  Use grasping mouthparts and spines to catch prey

8. Respiration, Circulation, and Excretion  Gas exchange via diffusion  Simple nervous system with several GANGLIA  Some nerves run the length on their body  Control movement and send sensory information

9. Movement  Muscles extend the length of their bodies  Fluid in the pseudocoelom (hydrostatic skeleton)

10. Reproduction  SEXUAL REPRODUCTION; have separate males and females  Internal fertilization  Male deposits sperm in female reproductive tract

11. Trichinosis-Causing Worms  Roundworm Trichinella – live and mate in the intestines of their hosts  Larva travel through bloodstream and burrow into organs and tissues  Form cysts in muscles

12.  Filarial worms – found in the tropics  Threadlike, live in blood and lymph vessels of birds and mammals (sometimes humans)  Transmitted via mosquitoes

13. Ascarid Worms  Ascaris lumbricoides – causes malnutrition in more than 1 billion people  (see diagramming)  Puppies are ‘wormed’ to get rid of ascarid worms

14. Hookworm  Eggs hatch outside the body of the host and develop in the soil  Use teeth to burrow into the skin and enter the bloodstream  Travel through blood to the lungs and then down to the intestines  Suck the host’s blood; causes weakness