PlatyhelminthesPlatyhelminthes

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.

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

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

• Excretory Excretory - 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

• Endocrine Endocrine - 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 cycleContents

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

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

End of PresentationEnd of Presentation