Platyhelminthes pt 2 Digene trematodes and tapeworms Opisthaptor

Platyhelminthes pt 2 Digene trematodes and tapeworms

Opisthaptor Ectoparasite One host Monogenea Turbellaria Trematoda Acetabulum endoparasite Mollusc/vertebrate life cycle Cestoda Free living Microtriches Scolex Proglottids Cilia lost from ectoderm (parasitic lifestyle) Phylum Platyhelminthes

Di(2)-Gene(birth) • • 2 or more hosts Endoparasitic No cilia on skin, skin is syncytial Life cycle: Adults in definitive host (a vertebrate) reproduce sexually → eggs in host’s feces released into water → hatch into ciliated larva (=miricidium) → snail (intermediate host) → asexual reproduction → sporocyte → redia → cercaria released from snail → metacercaria encysts in 2 nd intermediate host (or forage in some cases) → ingested by definitive host

Schistosoma mansoni

200 million infected worldwide Leading cause of death of Egyptian men 20 -44 years old Adults live in mesenteric veins, veins associated with bladder Damage caused by unegested eggs (50% never released) Control: clean water, sewage control, snail reduction Exacerbating factors: poverty & ignorance, dams

Swimmer’s itch • Schistosoma sp. that infect ducks, muskrat

Blackspot disease: Uvulifer sp.

Fasciola hepatica (sheep liver fluke) F. gigantica (human liver fluke)

Dicrocoelium dendriticum = a bile duct fluke of ruminants such as sheep, goats, deer, pigs.

Tuesday November 13 th CMU Ballroom Make a team of 3 – 4 students & sign up on the poster outside SL 118 by October 16 th!! For more information: Tri-Beta Meeting October 2 nd 6: 00 SL 118 Chem Club Meeting October 3 rd 7: 00 HA 405 Or contact Marissa Schafer at marissaschafer@hotmail. com

Opisthaptor Ectoparasite One host Monogenea Turbellaria Trematoda Acetabulum endoparasite Mollusc/vertebrate life cycle Cestoda Free living Microtriches Scolex Proglottids Cilia lost from ectoderm (parasitic lifestyle) Phylum Platyhelminthes

Class Cestoda - Tapeworms • • Obligate endoparasites of vertebrates Lack digestive tract Have scolex for attachment to host Body divided into proglottids – Each proglottid = egg factory with its own ovary and testis (make up to 50, 000 eggs per proglottid) – Worm = hundreds to thousands of proglottids

General life cycle of tapeworms • Adult in intestine of definitive host → proglottids break off and pass with feces → eggs released from proglottid → eaten by intermediate host → oncosphere larva → intermed host ingested by definitive host → adult develops in intestine

Tapeworms Scolex

Echinococcus granulosis – a tapeworm of dogs & dingoes

Dipylidium caninum

Beef tapeworm: Taenia saginata Attains a length of 10 m

Ligula intestinalis • Egg → copepod (encycts as a procercoid) → fish (encysts as a plerocercoid larva) → ingested by final host → adult tapeworm in gut of bird