Lecture 6 Parasite diversity 5 Cestodes, Monogenea, Acanthocephala Flashcards
Describe the class Cestoda found in Phylum Platyhelminthes.
tapeworms, endoparasites, adults in every class of vertberates, rare as adults in invertebrates
Describe morphology of class Cestoda found in Phylum Platyhelminthes.
- scolex (head); neck; strobila body: testes uterus
-strobila body is made up of gravid proglottid with eggs so each segment is called a proglottid
• polyzoic or monozoic ( both reproductive structure - > high reproductive output bc each segment can reproduce
• new proglottis via strobilation
-immature and new sgement (near scolex head)
Describe holdfast morphology of class Cestoda found in Phylum Platyhelminthes.
- variety of holdfast structures on scolex
- suckers, grooves, hooks, spines, glands, tentacles
- very important in species i.d.
What’s basic problem of endoparasite lifestyle?
to stay in place in final host bc body is trying to expell it
Name and describe holdfast structures of class Cestoda found in Phylum Platyhelminthes.
cestoda tegument suited for lifestyle
- acetabula “suckers”
- bothria open and close clampers
- bothridia more than 1 bothria
- microvilli/microtriches
- no digestive tract bc absorb nutrients in outer covering
Why care about morphology?
• both allow passage of glucose & sodium from outer covering and inc SA for absoprtion
- not all structures
equally
vulnerable
–>target of Praziquantel drug prevents strobilstion where maturing occurs
-
Describe Cestode life cycles.
• adults in gut of vertebrates
• 2 different hosts to complete life cycle
–>vertberates & invertebrates as intermediate hosts
• considerable variation among groups
–>life cycle & morphology of stages
Briefly outline Cestode life cycle.
final definitive host -> eggs in feces -> egg matures -> free-swimming larvae -> metacercariae-> larval form -> eaten by 2nd intermediate trophic transmission -> final host duck
Describe in detail life cycle of cestodes.
oncosphere; embryo develoment in water
-> coracidium; free-swimming hatches in water and eaten by copepod–> 1st intermediate copepod with juvenile metacestodes -> developed into mature procercoid-> 2nd intermdiate
plerocercoid-> infected fish eaten by carnivorous fish-> uncooked fish eaten by humans with cysticercus
-> intestine adult cestodes attach to wall
Describe Diphyllobothrium latum: in cestoda of platyhelminths
- broad fish tapeworm
* zoonotic for humans (accidental host)
Describe Taenia solium: in cestoda of platyhelminths
• pig tapeworm
• zoonotic for humans
-hyatid cyst large
Describe Echinococcus granulosus in cestoda of platyhelminths
• zoonotic problem
- domestic dogs definitive host, intermdiate host is livestock, unusual life cycle
- hyatid cyst large
Describe Triaenophorus crassus in cestoda of platyhelminths
• timing also important for consumption -> parasitic manipulation
- > 12 days, hang out top waer during day time more easily spooted.
- mature larvae yields bright red spot to be visually appealing and increase predation
what parasitic attack do Schistocephalus solidus cestodes?
biochemical manipulation
Describe Hymenolepis nana in cestoda of platyhelminths
- bird & mammal final hosts • unique life cycle -humans infected -wide size variation Polygonoporus giganticus -> huge
Describe Order Trypanorhyncha in cestoda of platyhelminths
• only in spiral valve of sharks and rays
• 4 armed tentacles on scolex
-diverse, more than 1 species in shark
Describe main characteristics of
Class Monogenea.
- main characters: many ectoparasites (primarily fish)-aquatic vertebrates
- some endoparasites -only 1 species in mammals
Describe basic structure of class Monogenea in Phylum Platyhelminthes.
- issues with ectoparasitic lifestyle?
- oral sucker/prohaptor, opsthaptor bottom section
- eyespots useless in endo
- ovary and testes, monicious-> no self-feritlization eyespot to see another species to mate -> inc reproductive success
- large reproductive structures to release large offspring to beat odds
what do opisthaptor reflect?
specific adaptations to host and site of infection
-extremem niche specialization
Describe life cycle of class Monogenea in Phylum Platyhelminthes.
• usually single-host –> direct transmission
- attach and develop, adults release eggs motile bc of eyespots , contact host then-hatch onto oncomiracidium
- short, free-swimming stage
- sensitive to cues ex mucus from fish detected
Oncomiracidium need water, but what factor makes eggs special in monogenea?
doesn’t produce eggs because of hibernation in frogs, takes too much energy to produce in winter
Describe how eggs are produced in frog life cycle and which months do what?
hibernation -> april gravid egg producing -> host breeding – gonadotropin increase in may -> june eggs released
-> october in gravid
Describe Phylum Acanthocephala.
-“thorny-headed” worm (retractable proboscis)
• not as abundant or diverse as other worms
• all endoparasites -vertebrate intesti
Describe Phylum Acanthocephala morphology.
retracteable proboscis
- diecious, serparate male and female
- no digestive structure same phylum as cestodes but absorb nutrients from outer covering
Acanthocephalan life cycles
• at least 2 hosts involved
-1st is arthropod
-paratenic
hosts common
egg released in water -> acanthor/egg coat with fibers -> acanthella larval stage in arthropod
->cystacanth -bright orange spot in arthropod -> cystacinth in paratenic host -> final host
diverisity of acanthocephala
Pomphorhynchus laevia & gammarid,
-Moniliformis
moniliformis & rat has cystacinth ; cockroach-acanthor inside)
