They are dorsoventrally flattened and bilaterally symmetrical
Flatworms are covered by a membrane called tegument
Most flatworms are hermaphroditic, except for Schistosoma sp.
Flatworms include Tapeworms and Flukes
They are multicellular animals characterized by a flat, bilaterally symmetric body
Flatworms are hermaphroditic, having both male and female reproductive organs in the same individual
The overall size of flatworms varies greatly, ranging from 1 mm to 20 meters or longer
The classes Cestoda (tapeworms) and Trematoda (flukes) contain species parasitic to humans
Cestodes are tapeworms with flat, segmented bodies of various lengths
Each proglottid of a tapeworm develops both male and female reproductive organs, with mature eggs developing in the most distal proglottids
Tapeworms have no circulatory system or digestive tract
Tapeworms are diagnosed by finding eggs or proglottids in the feces
Habitat of adult tapeworm: intestine of the Definitive Host (DH)
Taenia species (example)
Adult worms are seen in the intestine
Proglottids contain male and female parts
Eggs have 6 hooked embryos
Tapeworms have a ribbon-like body, flat, and require an intermediate host
Cestodes consist of three basic portions: Scolex, Neck (germinal portion), and Strobila (immature, mature, gravid proglottids)
Scolex is for attachment, with a rostellum armed with hooks and suckers
Strobila segments bud from behind the scolex and are immature, then mature and fill with eggs, becoming "gravid" proglottids
Immature proglottids have undifferentiated reproductive organs, while mature proglottids have differentiated reproductive organs
Gravid proglottids have a uterus with lateral branches filled with eggs
Species of Cestoda that require a vertebrate intermediate host include Taenia solium, Taenia saginata, and Echinococcus granulosus
Species of Cestoda that require an invertebrate intermediate host include Dipylidium caninum, Hymenolepis diminuta, and Raillietina garrisoni
Species of Cestoda that may or may not require an intermediate host include Hymenolepis nana
Species of Cestoda that infect humans in their larval stages include Echinococcus granulosus, Echinococcus multilocularis, Taenia solium, and Diphyllobothrium latum
Binomial names and common names of Cestoda species
Taenia saginata - Beef Tapeworm
Taenia solium - Pork Tapeworm
Taenia multiceps - Coenurus Tapeworm
Echinococcus granulosus - Hydatid Tapeworm
Echinococcus multilocularis - The Multiloculate or Alveolar Hydatid Tapeworm
Hymenolepis nana - Dwarf Tapeworm
Hymenolepis diminuta - Rat Tapeworm
Dipylidium caninum - Double-pored Tapeworm
Diphyllobothrium latum - Broad Fish Tapeworm
Classification of Cestoda into Pseudophyllidean and Cyclophyllidean
Pseudophyllidean: Scolex is almond/spatulate with 2 slit-like grooves, uterus has no branching with pores, and eggs are operculated giving rise to ciliated larvae