Platyhelminthes (Flatworms) Bio 1413 General Zoology Lab (Ziser, 2008) [Exercise 9] Identifying Characteristics of Phylum: -three true tissue layers (triploblastic) -bilateral symmetry -no body cavity (acoelomate) -some simple organs & organ systems; no skeletal, circulatory or respiratory systems -simple excretory system of tubules with “flame cells” -incomplete or no digestive tract -most hermaphroditic -many highly specialized parasitic forms -most parasitic forms with complex life cycles including one or more intermediate hosts and one or more larval forms Cell Types and Characteristic Structures: epidermis parenchyma tissue gastrodermis “flame cells” circular and longitudinal muscle layers around body wall Body Organization: flattened body some simple organs & organ systems: eg. digestive, nervous, excretory, reproductive trematodes, monogenea and cestodes greatly modified for parasitc lifestyle tapeworms with scolex for attachment; buds proglottids fluke life cycle: egg  miracidium  sporocyst  redia  cercaria  adult tapeworm life cycle: egg  cysticercus (bladder worm)  adult Classification: Class: Turbellaria -free living, mostly aquatic; Dugesia, Bipalium Class: Trematoda -parasitic liver and blood flukes; Clonorchis EC Class: Monogenea -mostly external parasites of fish, Protopolystoma Class: Cestoda -tapeworms; Taenia, Lab Activities: 1. Read introduciton and descriptions of flatworms in the lab manual beginning on page 139. 2. Dugesia , A Live Planarian, (p 140) live: Dugesia (=Planaria) live: Bipalium (if available) • General external appearance • know: head, eyes, auricles • Observations Locomotion & Behavior • Feeding 3. Stained whole mounts (p142) slide: Planaria inj wm • know structures as assigned 4. Transverse sections of Planaria (p 142 & Fig 9-2) slide: Planaria cs • know structures as assigned • Be able to recognize which of three regions a section is from (anterior, pharyngeal or posterior) 5. Clonorchis, the liver fluke (p 147) Clonorchis, the Liver Fluke slide: Clonorchis sinensis wm • Know structures as assigned • Know where in the body they are found 6. Schistosoma, the human blood fluke (p 144) slide: Schistosoma mansoni male • be able to distinguish between male and female & female • know where in the body they are found 7. Fasciola, The sheep liver fluke (HO) slide: Fasciola hepatica wm • • • Use dissecting scope only! • • • • Compare general structure with that of Clonorchis • Use figure to identify: Oral and ventral sucker, mouth, yolk glands, testis, ovary, uterus 8. Trematode larvae (p144, 146) slides: cercaria, wm; redia wm redia & Cercaria Larvae redia & cercariae, wm • Be able to recognize these as a larval form of trematodes EC. 9. Class Monogenea (see illustrations p 148) slide: monogenetic trematode, wm Protopolystoma, frog parasite, most closely resembles Polystoma in fig 9-5; Note general appearance and distinguish from other classes of flatworms Know: anterior sucker, mouth, intestine, uterus anal suckers, hooks 10. Class Cestoda:The Tapeworms (p148) slides: Taenia solium, scolex, wm Taenia pisiformis gravid • Know structures as assigned proglottid, wm 11. Cestode larvae Cysticercus larva(bladderworm) slide: Taenia pisiformis cysticercus Use dissecting scope only! • Be able to recognize it as a larval form of tapeworms Demonstrations: • Planarian Organ Systems - note the various organs and organ systems found in these flatworms: digestive system: highly branched to deliver nutrients to tissues in the absence of a circulatory system; also note it is an incomplete digestive tract with a mouth but no anus. excretory system: paired tubules "powered" by ciliated 'flame cells' which drain to the outside of the animal nervous system: paired ventral nerve cords with collateral connecting branches and ganglia (=brain) in head; specialized sense organs with photoreceptors (eye spots) and chemoreceptors (auricles) muscular system: with both circular and longitudinal muscles in body wall reproductive system: well developed • Other examples of the class Turbellaria; all are free living • Trematode life cycle: note the many larval stages, you observed a cercaria in your lab activities, the slide here shows another Trematode larval stage, the redia • Cestode life cycle: most tapeworms have a single larval form the cysticercus or bladder worm shown on the demonstration scope. Notebook Suggestions:  Make notes and observations on the living organisms available for study, how do they move, were you able to get any to eat, how long did it take, etc

 Describe some of the special adaptations seen in the parasitic classes that enhance their ability to find and survive in a host

 How do the larval forms of the trematodes and the cestodes differ and how do their life cycles differ?