• They are flatworms

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PHYLUM

PLATEYHELMINTHES

MR. LAOYE, BABAFEMI. J.

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CHARACTERISTICS

• They are flatworms

• Triploblastic

• Bilaterally symmetrical

• Dorsoventrally flattened

• Digestive system lacking or with muscular pharynx

• Possess single a single opening performing dual functions

• They are mostly parasitic

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Characteristics contd

• They are acoelomate animals

• They have a central nervous system

• They are mostly monoecious

• Excretion is via the protonephridia or flame cells

• Possess no respiratory system

• Possess no hard skeleton

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CLASSES OF PHYLUM PLATEYHELMINTHES

• CLASS TURBELLARIA

• CLASS TREMATODA

• CLASS CESTODA

• CLASS MONOGENEA

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CLASS TURBELLARIA

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CLASS TURBELLARIA

• Reproduce sexually and asexually

• An example is Dugesia (Planaria)

• Free living organisms

• Average length is 3-15 mm

• First set of invertebrate to possess an alimentary canal.

• Possess rhabdite

• Respiration is via body surface

• They practice cross fertilization

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CLASS TREMATODA

• Largest class of this phylum

• Consists of flukes which are endoparasites

• They are have thick protective covering on them called tegument

• They posses suckers

• Example is Fasciola hepatica.

• It is hermaphrodite

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CLASS TREMATODA

• All parasitic mostly in various internal organs of vertebrates including humans

• Syncytial tegument with many folds to increase surface area

• Oral and ventral suckers; Incomplete digestive system (mouth- pharynx- blind caecum or caeca)

• Monoecious except for the schistosomes (which are dioecious)

• Examples: Schistosoma, Fasciola.

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CLASS CESTODA

• Cestodes are segmented.

• Parasitic worms

• Sizes vary from a few millimetres to several metres.

• The adult worm consists of three parts scolex, neck and trunk.

• The head carries grooved or cup-like suckers, which are the organs of attachment to intestinal mucosa of the definitive host, human or

animal

• Examples are beef tapeworm (Taenia saginata) and pork tapeworm Taenia solium)

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CLASS CESTODA

• Exclusively parasitic

• Adults are enteric parasites

• Larvae are tissue parasites of invertebrate & vertebrate intermediate hosts.

• Body regions: rostellated or unrostellated scolex with suckers, neck

• Strobila made of immature, mature and gravid proglittids (segments)

• No digestive tract

• Monoecious proglottids; THUS DESCRIBED AS POLYZOOIC.

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DISEASES AND TREATMENT

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