Tapeworms Flashcards
Like flukes, tapeworms are also:
hermaphroditic
Tapeworms are ALWAYS_________, and the adult tape worms are always found in the ________ or in a connecting duct.
1) endoparasites
2) gastrointestinal tract
What is the class of “true tapeworms”?
Eucestoda
How do tapeworms take in their nutrients? This means that tape worms lack a _______ __________.
1) absorb through their body wall
2) body cavity
What morphological trait varies greatly in tapeworms?
size (length)
Three parts that make up the “body” of tapeworms:
1) scolex or “head”
2) short neck
3) strobila made up of segments called proglottids
The four suckers on the scolex are known as _______. A scolex is said to be _______ if it has a __________.
1) acetabulum (vinegar cup)
2) armed (unarmed if there is no rostellum)
3) rostellum: “retractable nose” which may be covered with backward facing hooks
The scolex serves as the ______ _______.
holdfast organ: anchor the adult tapeworm in the small intestine
The neck is the ______ _______.
germinal region: the rest of the body of the tapeworm develops from the neck
Each proglottid has ….
one or two sets of male AND female reproductive organs; formed at the neck and pushed farther down the body as new proglottids are formed
3 basic types of proglottids:
immature: closest to neck and contain immature, nonfunctioning reproductive organs
mature: in the middle of the body with fully functioning reproductive organs (“teenagers” of proglottids)
gravid: farthest from neck and contain nonfunctioning reproductive organs; uterus is full of eggs
The eggs of tapeworms are set free from the body of the tapeworm when:
gravid proglottids break away from the main body and the proglottid disintegrates and releases eggs; sometimes, single eggs released from uterus when pushed out by internal pressure
An egg is also known as:
oncosphere
Proglottids containing eggs are
voided in the feces of the definitive host.
A larval tapeworm is a
mestacestode
Life cycle of tapeworms:
1) Definitive host ingests intermediate host containing metacestode.
2) Scolices “excyst” and attach to the mucosa of the small intestine of the definitive host.
3) Scolex grows neck, neck grows proglottid, and adult tapeworm matures in intestine of definitive host.
4) Eggs are released from definitive host, and embryophore (envelope around oncosphere with 3 hooklets) is digested by intermediate host.
5) Oncosphere is released and travels to extraintestinal predilection site where the metacestode stage is formed
What are the four different metacestode stages?
cysticercoid, cysticercus, coenurus, hydatid
Cysticercoid stage:
single scolex; small, fluid filled cavity formed; found in mites and fleas
Cysticercus stage:
found in vertebrates as a single “inside out” scolex in a large, fluid filled cavity
Coenurus stage:
large, fluid filled cavity with many “inside out” (invaginated) scolices; “multi-headed” cysticercus
Hydatid stage:
Large fluid filled cavity with brood capsules inside; brood capsules contain many protoscolices
Brief illustration of tapeworm development stages:
oncosphere ——cysticercoid OR cysticercus OR coenurus OR hydatid metacestode stage—–ingestion—-adult tapeworm
Describe morphological traits of Cysticercoide tapeworms:
No rostellum on suckers (unarmed)
Usually wider than they are long (“squatty body”)
Innermost oncosphere covering known as “pyriform apparatus” and is pear-shaped
