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Worm Phyla: Platyhelminthes (flatworms - acoelomates) Nematoda (roundworms - pseudocoelomates) Annelida (segmented worms – coelomates) Phylum #1 Platyhelminthes (flatworms) Classes: 1. Turbellaria (free-living) 2. Trematoda (parasitic) 3. Cestoda (parasitic) Phylum Platyhelminthes ("flatworms") Evolved from Cnidarians, gained bilateral symmetry and developed excretory, nervous and reproductive systems. Bilateral, acoelomates. Digestion = single opening (mouth and pharnyx) and digestive cavity. Excretory = flame cells excrete wastes. No circulatory or respiratory systems; diffusion only for O2 / CO2 exchange. Sexual (hermaphrodites) and asexual reproduction regeneration. Class #1 Turbellaria (Phylum Platyhelminthes) free-living scavengers branched intestines with pharynx tube eyespots, can learn (chopped up & fed to others...) hermaphroditic; sexually reproduce A variety of marine turbellarians Eurylepta This turbellarian flatworm mimics a (very unsavory) sea slug Marine Flatworms mating Class #2 Trematoda - flukes (Still Phylum Platyhelminthes) Parasitic (species-specific) Thick, protective "tegument" resists acids/enzymes No digestive system (diffusion only for gases / food) no eyespots; very little cephalization Ex: Swimmer's itch, Schistosoma, Liver flukes Sheep liver fluke Sheep livers with trematode fluke Schistosoma male/female Schistosoma male / female blood flukes Typical Schistosoma egg Schistosome eggs, which may become lodged within the hosts intestinal wall or in liver, are the major cause of pathology in schistosomiasis. Class # 3 Cestoda (tapeworms) (still Phylum Platyhelminthes) • parasites (mostly mild symptoms in wellnourished people) scolex (head with hooks) proglottids (egg cases) Ex: Diplydium (cat intestines feces larval fleas adult fleas another cat ingested by licking fur) Scolex of tapeworm Nereis closeup Methane hydrate deposits on the ocean floor teem with life. Residents include ferocious polychaete ice worms that burrow into the formations and defend their lairs against intruders. Tapeworm (Class Cestoda) •Scolex and proglottids Phylum Nematodes (roundworms) Evolution- gained body cavity (pseudocoelom), separate sexes, and complete digestive system (2 openings). Bilateral symmetry. Dioeciuos– not hermaphrodites. Complete digestive system (two openings). Circulation and respiration through diffusion. Nematodes are pseudocoelomates DISEASES Pinworm (Enterobius sp.): eggs swallowed (dust/food) lg. intestine (lay eggs) anus (itching) Lungworm (Ascaris sp.): eggs swallowed penetrate to lungs throat swallowed intestine (lay eggs) Trichinosis: cysts ingested (pork, bear) intestine (pain, diarrhea, fever) blood muscles (lumps, pain) Hookworm (Huck Finn disease): bloodstream push abdomen through intestine eggs outside Brainworms, heartworms, Guinea worms (“the fiery serpent” makes great tattoos!), Filaria (clog lymph: elephantiasis), Loa loa (eyeworms) The Fiery Serpent- Guinea Worm Trichina-- a roundworm (nematode) common in pork • picture shows capsule embedded in muscle tissue. • enters host via raw or poorly cooked meat • eggs shed in the gastrointestinal tract--> feces • eggs eaten by herbivores --> encyst in muscle • encysted worm is resistant to antihelmithic drugs. Heartworm-a parasitic nematode Pinworms-- infections of kids (itchy eggs!) Reminder: Kingdom Animalia; Phylum Nematoda Phylum Annelida The Segmented Worms Evolution-development of coelom. Cephalization! Well-developed nervous system: nerve cord with ganglion in each segment and anterior brain Bilaterally symmetrical Organs within a true coelom (cavity within mesoderm) Compartmentalization of organs / movement of parts of body Closed circulatory system with five pairs of “aortic arches” Most have red hemoglobin in blood (efficient) Sophisticated digestive system: mouth pharynx esophagus crop gizzard intestine anus Appendages: Setae &/or parapodia Excretion- Nephridia remove nitrogenous wastes; wets skin Respiration—use diffusion Most hermaphroditic, some dioecious. Classes of Annelids Oligochaeta: earthworms, nightcrawlers, (aquatic) tubifex worms 20-45 tons of soil/year/acre processed by worms on organic farms each worm processes its own weight each day Polychaeta: bristleworms, tube worms, featherdusters marine worms with parapodia and (most) jaws! Hirudinea: terrestrial / aquatic leeches some parasitic, some free-living •medicinal anticoagulant “hirudin” Fanworm A filter-feeding polychaete: feather-duster Bristle-worm (nereis) The medicinal leech is best known as the organism used for blood letting (people used to believe many health problems caused by "bad" blood). They are being used once again to remove blood from hematomas (areas of blood leakage) resulting from surgery (like re-attaching severed limbs, etc.). http://www.sp.uconn.edu/~mcbstaff/ graf/AvHm/MedUsemain.htm