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Phylum: Platyhelminthes (flatworms) Greek "platy"' flat "helminth" worm General Characteristics 1. Bilateral symmetry – right/left sides 2. Cephalization – head (concentration of nervous tissue) 3. Aceolomate – no coelom (body cavity) 4. 3 cell layers 5. Incomplete digestive system – mouth, intestine, NO anus (diffuse/skin or out of mouth) 6. Nerve net – nerves that intertwine 7. Hermaphroditic – both types of sex organs in one body 1. Endoderm – inside layer – Fertilized egg (zygote) is of cells laid in cocoon 2. Mesoderm – middle 8. Respiration – occurs layer of cells through diffusion 3. Ectoderm – outer layer of cells Class Turbellaria Fresh water, free living (nonparasitic) Example: Planaria Structure of Turbellaria a. Epidermis – exterior layer; contain pigment b. Muscle fibers – run in all directions c. Parenchyma – cells that fill space (no function) d. Eyespots – light sensitive, 2 ocelli e. Cilia – ventral surface, movement f. Mouth – midventral opening g. Pharynx – sucks up food h. Gastrovascular cavity – intestine, digests food i. Flame Cell – cell that removes cellular waste j. Genital pore – opening through which sperm and eggs pass Anatomy Class Trematoda Flukes, ALL ARE PARASITIC! 1. 2. 3. 4. 5. 6. Example: liver fluke Tegument – waxy coating over body (protect it from the host) Glands – produce cyst stage Suckers and hooks – used to attach to body of host Sense organs – poorly developed Reproductive host a. definitive host – in which fluke reproduces sexually b. intermediate host – in which fluke reproduces asexually Life Cycle of the Liver Fluke 1 The adult liver fluke in the human liver. 2 The fertilized eggs are lost with the feces. 3 The ciliated larva burrows into a snail. 4 Another type of larva, which has been reproduced asexually, leaves the snail. 5 Each of these larvae forms a resistant cyst. 6 The cyst remains on plants, such as water cress; which is eaten by humans. Class Cestoda meaning: “belt” 1. Example: tapeworms 2. Structure a. Long (flat bodies) • Muscles well developed b. Proglottids – segments made by budding • Sex organ found here c. Tegument – waxy coating • Absorbs nutrients – No digestive system d. No special sense organs Adult Tapeworms in Small Intestines Scolex • Head, hooks, suckers Tapeworm Life Cycle 1 The adult tapeworm in the human gut. 2 Mature segments leave the gut in the feces. 3 The segments are eaten by a pig. 4 The eggs hatch into larvae in the pig's gut. 5 The larvae burrow into the muscles of the pig and form cysts. 6 The cysts are introduced into the human gut if undercooked pork is eaten. World Longest Tapeworm… The longest tapeworm ever removed from a human came out of Sally Mae Wallace on September 05, 1991. In all, doctors pulled 37 feet of tapeworm out of Sally Mae Wallace's body through her mouth. If you find all of this disgusting, be glad you're not a whale as tapeworms in whales can grow up to 120 feet long. How about a tapeworm diet? • While it's unclear if this diet is more of an urban legend than a truth… • There are posters touting the wonders of pills with tapeworm segments in them. • The opera star Maria Callas who liked eating raw meat (a source of tapeworms), may have been an unwitting beneficiary of this weight loss plan, which wormed its way into popular use in the 1920s. Phylum Nematoda: The Round Worms Characteristics •There are over 80,000 species of round worms •Some are aquatic, most are parasitic 1. Cylindrical, unsegmented, with tapering ends. 2. Pseudocoeloemates • Cavity partially lined with tissues from mesoderm 3. Digestive Tract with TWO openings – mouth and anus 4. Diffusion through body walls 5. Simple nervous system with some sense organs 6. Effective hydroskeleton and musculature 7. Reproduce SEXUALLY – most speces have separate sexes • Females can produce ~100,000 eggs a day. Parasitic Nematodes: Hookworm •Eggs hatch outside the body and develop in soil. •Use sharp hooks and teeth to burrow into skin and enter bloodstream •Travel from blood > lungs > intestines •Suck blood = weakness and poor growth Heartworms Guinea Worms: •Tiny infected water flea are drunk up from standing water •Inside human, grows and matures up to 3 ft •After a year, worm emerges through painful blister Filarial Worm (causes elephantiasis) •Live in Blood and Lymph vessels •Transmitted through biting insects (mosquitoes) •Blocking of lymph passages = elephantiasis Trichinosis •Caused by Trichinella roundworm •Adults live and mate in hosts •Females burrow into intestine and release larvae •Larvae travel in bloodstream, burrowing into organs/tissues causing terrible pain •Larvae form cysts that become inactive Ascarid Worms 1. Spread by eating contaminated food with Ascaris eggs 2. Eggs hatch in intestine, burrow in walls, and enter blood vessels • Carried through BV to lungs, spread into air passages/throat, get swallowed and cycle begins again 3. Ascaris matures in host intestine and produce large #’s of eggs • Leave body in feces These are the worms that we “de-worm” in puppies and kittens