Part 1 Cestodes:

Planarian Regeneration

Longitudinal cut- can cut two heads

Different cuts can produce different looking worms


-Adaptations towards parasitic existence

-Increased reproduction capacity, Millions of eggs during life time, only some will make it- one host to another, never make it to another host

-r selection – from logistic growth equation , maximizing reproduction rate, putting out lots of offspring

-Complete loss of digestive track no mouth, lots of surface area

-No Brain in the “Head Area”


Testies and ovaries

Proglottids are produced old ones move along down the worm

Can get 30-40ft in human intestine

Strobalization: Growing in pieces, asexual reproduction

Monoecious- both testies and overies, uterus, genital opening

Can self fertilize, two worms cross fertilize

Life Cycle of Beef Tapeworm- Definitive host: human, intermediate host: cow

Once Zygotes develop onchospheres (the covering), how it can be spread if cow ingests

Cysticercus forms in muscle of cows

Tapeworm is not as prevalent in the US, in less sanitary areas more cases-social injustice issue

Part 2 Trematodes (with Monogeneans)

Class Monogenea

-Ectoparasites live on body surfaces of fish and other aquatic organisms

-Hooks on outer surface of hosts with haptors, anterior oral suckers

-Single host, no intermediate host (mono)

Class Trematoda

-Has some digestive tract has mouth and oral sucker

  • Complicated life cycles different stages
  • Sheep liver fluke, large in size
  • Feeding on liver

Disease called schistosomiasis second most prevalent disease compared to malaria – from schistosomes

-Around rivers used for laundry, waste, eating and drinking- health issues (around Nile River)

Representative Flukes- self and cross fertilization

Most flukes have free living stage called merisidium- larvae that hatches out of egg, then develops germ balls

-Different intermediate hosts inverts and verts

Part 3 More on Trematodes

-Stages are different in different kinds of Flukes

  • Organisms need to find host- rapid asexual is key


-Secondary rounding

-Female situated in the body of a male

-Female more rounded, fixed in groove, diecious

-Schistosomes- 1 intermediate host, when adults in body of human lives in circulatory system, finds way to blood vessels in intestines and shed eggs into the feces

-Different schistosomes effect different part of the body




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