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Phylum Platyhelmenthes Planarians, Flukes, & Tapeworms. Simple acoeleomates Bilaterally symmetrical Most flattened "Dorsoventrally" Divided into 4 classes:. Class Turbellaria. Most free-living and non parasitic Include planarians Lack circulatory and gas-exchange organs.
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Phylum PlatyhelmenthesPlanarians, Flukes, & Tapeworms Simple acoeleomates Bilaterally symmetrical Most flattened "Dorsoventrally" Divided into 4 classes:
Class Turbellaria • Most free-living and non parasitic • Include planarians • Lack circulatory and gas-exchange organs. • Simple excretory structures called flame cells that maintain osmotic balance. • Is cephalized and has eye-spots which are sensitive to light • Feeds through ventral feeding tube called a pharanx • Can reproduce sexually, or asexually through regeneration
Class Trematoda (Flukes) • Similar in form to turbillarians • Many are parasitic. Example of parasitic fluke is the asian liver fluke • Many have complex life cycles including multiple hosts and alternation of generations.
Liver Flukes Cont’d… Liver Fluke Liver Fluke encysted in a liver
Class Cestoda (Tapeworms) • Parasitic flatworms • Can grow to enormous lengths (up to 20m) • Parasitize mostly vertebrate hosts • Attach head named scolexto intestinal walls of host, and abosrb host's nutrients • Following scolex is a series of repeating structural units called proglottids • Mature proglottids containing thousands of eggs are released with the host's feces to infect other organisms.
