Class Cestoda Flashcards
Skeletal, circulatory, and respiratory systems are usually _____
absent
Important differences between cestodes and trematodes
(1) Cestodes have a flat tape-like or ribbon-like body
(2) Cestode’s body is made up of hermaphroditic segments
(3) They lack mouth and digestive tract
(4) They are exclusively endoparasitic in vertebrate’s gut
(5) Their larvae infect both vertebrates and invertebrates
proglottids
hermaphroditic segments
the whole chain of proglottids
strobila
With direct access to food and having _______ gut was lost (evolutionary history)
saprozoic nutrition
saprozoic nutrition
feeding on liquid organic material
_____ and _____ are continuous between _____ in cestodes
tegument
muscles
proglottids
polyzoic
Cestodes with many proglottids
monozoic
1 set of reproductive organs
Apolysis
release of gravid proglottids from the host
Adult body consists of 3 distinct regions:
scolex, neck, and strobila
acetabulate scolex
it’s cup shaped, circular in outline and with a heavy muscular wall with 4 muscular suction cups
Hooks and rostellum are present
Armed scolex
with hooks
bothraite scolex
presence of 2, (rarely 4 or 6) longitudinally arranged, shallow grooves, with weak suction powers
Glands are present
Rostellum
small rounded projection bearing hooks on the apex of the scolex of some tapeworms
Neck
Below the scolex
zone of proliferation, containing stem cells
From this zone, new segments or proglottids differentiate
Drug of choice
Praziquantel destroys integument
the _____ proglottids have the least developed reproductive systems, while the _______ ones are more reproductively developed
anterior-most
more posterior
Strobila is grouped into 3 regions
immature, mature and gravid proglottids
Immature proglottids
reproductive organs are visible but are nonfunctional
Mature proglottids
reproductive organs are fully functional
Gravid proglottids
filled with eggs or shelled embryos
A proglottid can _______ with itself
copulate
When proglottid reaches the end of strobila:
it detaches and passes out of the host intact with feces
Anapolysis
proglottids disintegrate in route, releasing the eggs
Site of nutrient absorption
Tegument (no gut is present)
Differences in tegument of cestodes vs trematodes
Tegument is covered by minute projections called microtriches as well as a glycocalyx
Microthrix
has an apical tip that is anchored to host’s intestinal epithelium and provide resistance to the movement of the intestine
Agitate walls increasing accessibility to nutrients
Glycocalyx
a layer of carbohydrate containing macromolecules, covers the entire tegument surface
Protects worm form digestive enzymes
tegumental musculature
located between two cytoplasmic regions
consists of outer circular muscles and the inner longitudinal muscles
Cytom
Sote for protein synthesis
Their reproductive systems differ from trematodes in that:
(1) the uterus meets with a dead-end
(2) separate vaginal canal is present
(3) self fertilization may occur
Male sperms pathway
Testis –> single Vas efferens –> Vas deferens –> Cirrus
females reproductive system
ovary (produces ova) –> oviduct (site of fertilization) –> ootype (oviduct region)
Ootype has structures that are involved in
eggshell formation
Sperm is deposited in
the seminal vesicle and stored until there are eggs to be fertilized
During copulation, ____ of one proglottid is inserted into the ____ of another proglottid, either ___________ and sperms are ejaculated
cirrus
vagina
the same or different worm
hypodermic impregnation
cirrus is forced through the body wall
________ is desired to insure vitality and prevent too much inbreeding
Cross fertilization
The eggs unlike trematoda lack
an operculum
oncosphere
embryonic membranes that serve as protective coverings of the embryo
Oncosphere contains
6 elongated hooks
Oncosphere enclosed by
inner envelope and then an embryophore
3 egg types
pseudophyllidean, Dipylidium, and taenioid
Example of pseudophyllidean
Diphyllobothrium latum
Example of Dipylidium
Dipylidium and Hymenolepis
Example of Taeniidae
Echinococcus and Taenia
Pseudophyllidean Pattern:
Once the eggs containing coracidia leaves the host feces and meet water, the larvae escapes from the shell through the operculum swims using its ciliated embryophore
1st intermediate host
Aquatic arthropods
Once embryophore reaches 1st host:
it trasnforms into a procercoid
2nd intermediate host
Fish
When the 2nd intermediate host, a fish, ingests the infected arthropod:
It migrates to muscle and other tissues and transforms into a plerocercoid
Infective stage:
Plerocercoid
When the infected fish is eaten by a human:
it attaches to the wall of the small intestine, and strobilization begins
2 patterns for life cycle
Cyclophyllidean Pattern
Pseudophyllidean Pattern
embryo=
oncosphere
Cyclophyllidean Pattern:
Eggs are inactive until eaten by an intermediate host
Intermediate host
Crustaceans
In crustaceans
eggs hatch in the gut and oncosphere employs its 6 hooks to enter hemocoel transforming into cysticercoid
In a vertebrate intermediate host
after ingestion, The systemic circulation carries it to several areas of the body, where it develops into a cysticercus
coenurus cyst
bladder wall develops several invaginated scolices
hydatid cyst
formed as invaginations on the walls forming brood capsules
