Cestodes (Flatworms) Flashcards
What is the phylum of cestodes and trematodes?
Platyhelminthes
Do Platyhelminthes have a body cavity?
no
2 subclasses of cestodes?
Eucestoda (true tapeworms)
Cotyloda (pseudotapeworms)
Is life cycle of tapeworm always direct or indirect?
indirect
How many intermediate hosts to tapeworms require?
one or two
What are the intermediate hosts of tapeworms?
arthropods
fish
mammals
Are domestic animals intermediate or definitive hosts of tapeworms?
intermediate
definitive, or
both
What are larval stages of domestic animal tapeworms called?
bladderworms
What path do bladderworms take after ingested by definitive host?
released from tissue of intermediate host and develop into adult tapeworms within digestive tract of definitive host.
What are the solid bodied cestodes?
procercoid
plerocercoid
tetrathyridium
How do domestic animals become infected with larval stages of tapeworms?
Ingestion of cestode egg or procercoid
Body of tapeworm?
long
dorsoventrally flattened
3 regions
scolex: head modified into attachment organ and
bears 2 to 4 muscular suckers (acetabula)
rostellum is snout, fixed or retractable, may
have hooks
strobila: the body composed of segments
(proglottids) in diff stages of maturity
proglottids near neck = immature, then
sexually mature proglottids, then gravid
segments that contain eggs
Which part of eucestodes breaks off its body and passes out of definitive host in feces?
gravid proglottids
How do cestodes get nutrients?
nutrients absorbed directly through body wall
Which organs occur in each individual proglottid of cestodes?
both male and female reproductive organs
How do cestodes reproduce?
cross-fertilization
self-fertilization
Cestode egg?
contains fully developed embryo (has six hooks in three pairs) = hexacanth embryo or oncosphere
Life cycle of cestode?
gravid proglottid shed fully intact in feces (singly or in chains)
they then rupture and release eggs
eggs ingested by intermediate host
develop into metacestode stage
metacestode (larval) stage may be in the form of a cysticercus, a coenurus cyst, a hydiatid cyst, or a tetrathyridium
definitive host becomes infected after ingestion of an intermediate host that contains metacestode stage
juvenile tapeworm then emerges from metacestode stage, attaches to lining of small intestine, and begins to produce strobili.