Lecture 6 Parasite diversity 5 Cestodes, Monogenea, Acanthocephala

Question 1

Describe the class Cestoda found in Phylum Platyhelminthes.

Answer 1

tapeworms, endoparasites, adults in every class of vertberates, rare as adults in invertebrates

Question 2

Describe morphology of class Cestoda found in Phylum Platyhelminthes.

Answer 2

• 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)

Question 3

Describe holdfast morphology of class Cestoda found in Phylum Platyhelminthes.

Answer 3

• variety of holdfast structures on scolex
• suckers, grooves, hooks, spines, glands, tentacles
• very important in species i.d.

Question 4

What’s basic problem of endoparasite lifestyle?

Answer 4

to stay in place in final host bc body is trying to expell it

Question 5

Name and describe holdfast structures of class Cestoda found in Phylum Platyhelminthes.

Answer 5

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

Question 6

Why care about morphology?

Answer 6

• 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
-

Question 7

Describe Cestode life cycles.

Answer 7

• 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

Question 8

Briefly outline Cestode life cycle.

Answer 8

final definitive host -> eggs in feces -> egg matures -> free-swimming larvae -> metacercariae-> larval form -> eaten by 2nd intermediate trophic transmission -> final host duck

Question 9

Describe in detail life cycle of cestodes.

Answer 9

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

Question 10

Describe Diphyllobothrium latum: in cestoda of platyhelminths

Answer 10

• broad fish tapeworm

* zoonotic for humans (accidental host)

Question 11

Describe Taenia solium: in cestoda of platyhelminths

Answer 11

• pig tapeworm
• zoonotic for humans
-hyatid cyst large

Question 12

Describe Echinococcus granulosus in cestoda of platyhelminths

Answer 12

• zoonotic problem

• domestic dogs definitive host, intermdiate host is livestock, unusual life cycle
• hyatid cyst large

Question 13

Describe Triaenophorus crassus in cestoda of platyhelminths

Answer 13

• 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

Question 14

what parasitic attack do Schistocephalus solidus cestodes?

Answer 14

biochemical manipulation

Question 15

Describe Hymenolepis nana in cestoda of platyhelminths

Answer 15

- bird & mammal final hosts 
• unique life cycle
-humans infected
-wide size variation
Polygonoporus giganticus -> huge

Question 16

Describe Order Trypanorhyncha in cestoda of platyhelminths

Answer 16

• only in spiral valve of sharks and rays
• 4 armed tentacles on scolex
-diverse, more than 1 species in shark

Question 17

Describe main characteristics of

Class Monogenea.

Answer 17

• main characters: many ectoparasites (primarily fish)-aquatic vertebrates
• some endoparasites -only 1 species in mammals

Question 18

Describe basic structure of class Monogenea in Phylum Platyhelminthes.

Answer 18

• 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

Question 19

what do opisthaptor reflect?

Answer 19

specific adaptations to host and site of infection

-extremem niche specialization

Question 20

Describe life cycle of class Monogenea in Phylum Platyhelminthes.

Answer 20

• 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

Question 21

Oncomiracidium need water, but what factor makes eggs special in monogenea?

Answer 21

doesn’t produce eggs because of hibernation in frogs, takes too much energy to produce in winter

Question 22

Describe how eggs are produced in frog life cycle and which months do what?

Answer 22

hibernation -> april gravid egg producing -> host breeding – gonadotropin increase in may -> june eggs released
-> october in gravid

Question 23

Describe Phylum Acanthocephala.

Answer 23

-“thorny-headed” worm (retractable proboscis)
• not as abundant or diverse as other worms
• all endoparasites -vertebrate intesti

Question 24

Describe Phylum Acanthocephala morphology.

Answer 24

retracteable proboscis

• diecious, serparate male and female
• no digestive structure same phylum as cestodes but absorb nutrients from outer covering

Question 25

Acanthocephalan life cycles

Answer 25

• 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

Question 26

diverisity of acanthocephala

Answer 26

Pomphorhynchus laevia & gammarid,

-Moniliformis
moniliformis & rat has cystacinth ; cockroach-acanthor inside)