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WORMS. Phylum Annelida (Segmented Worms). 15,000 Annelid species Bilaterally symmetrical coelomates Coelomes divided into partitions by septa Inhabit marine, fresh water, & moist environments Has complex digestive system Has closed circulatory system
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Phylum Annelida(Segmented Worms) 15,000 Annelid species Bilaterally symmetrical coelomates Coelomes divided into partitions by septa Inhabit marine, fresh water, & moist environments Has complex digestive system Has closed circulatory system Epidermis is primary gas exchange organ Are hermaphroditic Reproduce sexually by cross fertilization Reproduce asexually through regeneration 3 Classes
Class Oligochaeta • Include earthworms • Extracts nutrients from soils • Extremely beneficial to farming as they enrich and aerate soils
The Earthworm Giant Earthworm – Amazon Basin
Class Polychaeta • Very similar to oligochaeta • Most are marine • Have paddle or ridge-like extensions on segments called parapodia • Aid in gas exchange and locomotion
Class Hirudinea (leeches) • Most inhabit fresh water, or moist terrestrial environments • Feed on small invertebrates or are parasitic • Have significant medicinal value in treating bruising, and as a source of Pharmaceuticals
Over 80000 species • Cylindrical pseudocoeloemates • Have effective hydroskeletonand musculature • Inhabit aquatic areas. Most are parasitic. • Most reproduce sexually. Females can produce ~100,000 eggs a day. • Tricininellaspiralis causes trichinosisin humans from under cooked pork • Parasite burrows into muscle tissue forming cysts • Hookwormsandpinwormscan parasitize digestive systems • Others cause heartwormandelephantiasis Phylum Nematoda:The Round Worms
Parasitic Nematodes: Roundworm Hookworm
Phylum Nemertina • Similar to flat worms • Inclideproboscus worms • Acoelomate, but have functioning digestive tract • Also have a funtioning blood vascular system
Phylum PlatyhelmenthesPlanarians, Flukes, & Tapeworms Bilaterally symmetrical Most flattened "Dorsoventrally" Divided into 4 classes: Simple acoeleomates
Class Turbellaria • Most free-living and non parasitic • Includeplanarians • Lack circulatory and gas-exchange organs. • Simple excretory structures called flame cells that maintain osmotic balance. • Is cephalizedand 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.