lecture 4

Question 1

what are parasitic helminths?

Answer 1

parasitic worm-like organisms that live in and feed off living hosts

Question 2

are helminths endoparasites or ectoparasites?

Answer 2

endoparasites

Question 3

where do helminths live as sexually mature adults?

Answer 3

the GI tract

Question 4

how do helminths injure their host? (2 ways)

Answer 4

mechanically and chemically

Question 5

what are the three groups of helminths?

Answer 5

• cestodes
• trematodes
• nematodes

Question 6

for the _____, each proglottid segment of the adult tapeworm is hermaphroditic

Answer 6

cestodes

Question 7

all _____ are hermaphrodites, except for the schistosomes

Answer 7

trematodes

Question 8

adult parasitic _____ have separate male and female worms

Answer 8

nematodes

Question 9

platyhelminths are flatworms because most are ________

Answer 9

dorsoventrally flattened

Question 10

what are the two classes of Phylum Platyhelminthes?

Answer 10

1. Class Cestoda - Tapeworms

2. Class Trematoda - Flukes

Question 11

what are the two subclasses of class cestoda?

Answer 11

1. subclass cestodaria

2. subclass eucestoda

Question 12

what are the two orders of subclass eucestoda?

Answer 12

1. order cyclophyllidea

2. order pseudophyllidea

Question 13

cestodes lack a ____ & a _____

Answer 13

mouth & a digestive tract

Question 14

what is the life cycle of a tapeworm?

Answer 14

the adult tapeworms live in the definitive host (predator) while the prey plays host to 
the intermediate stages.
o Eggs laid by the adult pass out 
in the feces of the definitive 
host and are eaten by the 
intermediate host.
o These develop into the 
intermediate stage, which 
generates the adult when 
eaten by the definitive host.
o A tapeworm may pass 
through several intermediate 
hosts before it finds the right  definitive host

Question 15

what are the intermediate hosts of tapeworms?

Answer 15

• a mammal
• an arthropod
• a fish
• a bird
• a reptile

Question 16

what are the 3 distinct regions of a cestode?

Answer 16

• scolex
• neck
• strobila

Question 17

what is a scolex?

Answer 17

the anterior point of attachment structure; a key feature in identifying the different tapeworms (NOT a mouth)

Question 18

whats the difference in the scolex structure between order cyclophyllidea and order pseudophyllidea?

Answer 18

1. order cyclophyllidea - scolex contains 4 suckers and sometimes hooks
2. order pseudophyllidea - scolex contains slit-like suckers or grooves called bothria

Question 19

what is the structure of the neck?

Answer 19

• undifferentiated/unsegmented region between the scolex and the strobila
• the narrowest part of the tapeworm
• contain stem cells that are responsible for giving rise to new proglottids

Question 20

what is the structure of the strobila?

Answer 20

linear series of segments or proglottids

Question 21

what are the three types of proglottids?

Answer 21

1. immature proglottids - newly formed
2. mature proglottids - possess both male and female sex organs
3. gravid proglottids - develop after mating; contain hundreds to thousand of embryonated eggs.

*each proglottid is an independently functioning unit

Question 22

which system develops first within the proglottid?

Answer 22

the male system

Question 23

the male organs disappear in ____ ____

Answer 23

gravid proglottids

Question 24

what are the structures of the female system?

Answer 24

• ovaries (always 2)
• vitelleria (yolk gland) - scattered or compact
• mehlis’ gland
• uterus (contains eggs in branches)
• vagina (carries sperm to ootype)
• common genital pore

Question 25

most of the female organs disappear in ___ ___, except for the _______

Answer 25

gravid proglottids

egg-filled uterus