Platyhelminthes

Contents Position in animal kingdom Taxonomy Some unique characteristics Systems 1 (Integumentary, Skeletal, Muscle and Digestive)Systems 1 Systems 2 (Excretory, Respiratory, Circulatory, and Nervous).Systems 2 Systems 3 (endocrine and Reproductive)Systems 3 Class TurbellariaTurbellaria Class TrematodaTrematoda Class CestodaCestoda

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.

Taxonomy Class Turbellaria (tur-bell-er-e-a)Class Turbellaria (tur-bell-er-e-a)  Dugesia Dugesia Class Monogenea (mon-o-gin-e-a)  No representatives Class Trematoda (trim-a-toe-da)Trematoda (trim-a-toe-da)  Clonorchis, Fasciola, Schistosoma ClonorchisFasciolaSchistosoma Class Cestoda (ces-toe-da)Cestoda  Taenia, Dipylidium Echinococcus TaeniaDipylidium 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 Contents

Systems 1 IntegumentaryIntegumentary - Rhabdites and one cell layer epidermis in Turbellaria and usually ciliated; syncytial tegument in other classes. SkeletalSkeletal - hydrostatic MuscleMuscle - longitudinal, transverse, and circular muscles are present. DigestiveDigestive - incomplete with intracellular and extracellular digestion; no system in Cestoda.

Systems 2 ExcretoryExcretory - flame cells, or excretory tubes in Cestoda. RespiratoryRespiratory - no system, diffusion CirculatoryCirculatory - none, diffusion. NervousNervous - anterior ganglia, ventral ladder-like system (two lateral cords with transverse cords). Contents

Systems 3 EndocrineEndocrine - hormones produced by nervous system ReproductiveReproductive - 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

Clonorchis Human liver fluke - has two intermediate or secondary host snail and fish. Contents Cerceria Human liver fluke

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 Taenia  Dipylidium Dipylidium  Echinococcus Echinococcus Contents

Taenia Proglotid Contents

Dipylidium (dog tape) Juveniles in flea and louse Note the two gential pores and reproductive systems in each proglottid. Proglottid Contents

Echinococcus Hydatid cyst (cysticercus)- may scolices and enlarges to as large as a basketball. Often called sand. Only three proglottids Contents

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