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Platyhelminthes. Contents. Position in animal kingdom Taxonomy Some unique characteristics Systems 1 (Integumentary, Skeletal, Muscle and Digestive) Systems 2 (Excretory, Respiratory, Circulatory, and Nervous). Systems 3 (endocrine and Reproductive) Class Turbellaria Class Trematoda
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Contents • Position in animal kingdom • Taxonomy • Some unique characteristics • Systems 1 (Integumentary, Skeletal, Muscle and Digestive) • Systems 2 (Excretory, Respiratory, Circulatory, and Nervous). • Systems 3 (endocrine and Reproductive) • Class Turbellaria • Class Trematoda • Class Cestoda
Platyhelminthes • Eumetazoa - animals with tissue • Bilateria - have bilateral symmetry and are triploblastic. • Protostomia - a group of animals whose mouth develops from the blastopore, and the mesoderm forms from an area near the blastopore. • Acoelomata - They have a true mesoderm which fills the original blastocoel between the outer epidermis and digestive tract.
Contents Taxonomy • Class Turbellaria (tur-bell-er-e-a) • Dugesia • Class Monogenea (mon-o-gin-e-a) • No representatives • Class Trematoda (trim-a-toe-da) • Clonorchis, Fasciola, Schistosoma • Class Cestoda(ces-toe-da) • Taenia, Dipylidium Echinococcus
Contents Some Unique Characteristics • Proglotids and scolex in Cestoda • Rabdites in Turbellaria • Combination of characteristics- flame cells and being acoelomates for example. • Larva of each class are unique
Systems 1 • Integumentary- Rhabdites and one cell layer epidermis in Turbellaria and usually ciliated; syncytial tegument in other classes. • Skeletal - hydrostatic • Muscle - longitudinal, transverse, and circular muscles are present. • Digestive - incomplete with intracellular and extracellular digestion; no system in Cestoda.
Contents Systems 2 • Excretory - flame cells, or excretory tubes in Cestoda. • Respiratory - no system, diffusion • Circulatory - none, diffusion. • Nervous - anterior ganglia, ventral ladder-like system (two lateral cords with transverse cords).
Contents Systems 3 • Endocrine - hormones produced by nervous system • Reproductive - monoecious in most • Well developed reproductive organs, mostly internal fertilization. • Two of the parasitic classes have complex life cycles • Trematoda - miracidium, sporocyst, redia, cercaria, metacercaria (usually snail is secondary host. • Cestoda - oncosphere, cystercercius (bladderworm)
Contents Class Turbellaria • Planaria -Free-living flatworms with soft flattened bodies covered with ciliated epidermis which has special secreting cells called rabdites. Dugesia
Contents Class Trematoda • Flukes -oral and ventral suckers, no hooks, parasites, body with a syncytial tegument without cilia. Larva stages unique. • Clonorchis • Fasciola • Schistosoma
Contents Human liver fluke Cerceria Clonorchis • Human liver fluke - has two intermediate or secondary host snail and fish.
Contents Fasciola • Sheep liver fluke - metacercaria on grass. Life cycle
Contents Fasciola life cycle
Contents Schistosoma • Blood Flukes • Cerceria usually infect by burrowing through skin.
Contents Class Cestoda • Tapeworms • Have distinct head structure (Scolex) and reproductive units called proglottids. Do not have a digestive system. • Larva are oncospheres and cysticerci (bladder worms) • Taenia • Dipylidium • Echinococcus
Contents Taenia Proglotid
Contents Proglottid Dipylidium (dog tape) • Juveniles in flea and louse • Note the two gential pores and reproductive systems in each proglottid.
Contents Echinococcus • Hydatid cyst (cysticercus)- may scolices and enlarges to as large as a basketball. Often called sand. • Only three proglottids
