1. 36-2 Nematoda and Rotifera  Both phylum have bilateral symmetry  Both have fluid filled space which serves 4 functions 1. Holds internal organs 2. Serves as storage area for eggs and sperm 3. S upports body 4. Provides structure against which muscles can contract

2. Phylum Nematoda  Roundworms (transps. 134,135,158)  L ong slender bodies that taper at each end  K nown as pseudocoelomates *hollow fluid-filled cavity that is lined by mesoderm on outside, and endoderm on the inside 1 mm to 120cm in length

3. Phylum Nematoda  H ave digestive tract with 2 openings: anterior end is mouth and posterior end is anus. Food goes in mouth and moves in only 1 direction. This is better than a gastrovascular cavity.  Separate sexes  Protective noncellular covering called cuticle  Free living on land and in salt water or fresh water Some are parasites

4. 1. Genus: Ascaris   Parasitic in intestines of pigs, horses and humans (fig. 36-7 p.716)  1 ft. in length 1 female produces 200,000 eggs/day

5. Life Cycle   F ertilized eggs in feces of hosts  N ew host ingests contaminated food or water Eggs develop in intestines. Larvae form, go through bloodstream to lungs to throat. Coughed up and swallowed and returned to intestines.

6. 2. Hookworms   lways parasitic  F eed on host’s blood  L ife cycle similar to Ascaris Affect 400 million people. Especially in the tropical regions

7. 3. genus: Trichinella  P arasitic in walls of host’s intestines  L arvae go to muscles and form cysts Get by eating raw meat (usually pork). Called trichinosis. Pretty rare in the USA.

8. Other Parasitic Roundworms 1. Pinworm  M ost common in the USA  C auses no serious disease 2. F ilarial worms  P arasitic  U sually in the tropics  L arvae develop in the mosquito a.Elephantiasis: limbs accumulate excess water and swell b. heartworm disease: clogs arteries and heart of dogs (and some cats

9. Pinworm

10. Elephantiasis

11. Heartworm Disease

12. Phylum Rotifera  C alled rotifers  F ree living and transparent and in fresh water Can survive without water for a long time. They dry up and when wet conditions return, they resume life  S eparate sexes  D raw and label fig. 36-10 p. 718  D efine or explain purpose *cilia *mastax *cloaca

13. Rotifera