PHYLUM MYXOZOA

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PHYLUM MYXOZOA -- all parasites of fishes --
multicellular related to Cnidaria
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PHYLUM MYXOZOA -- all parasites of fishes --
multicellular related to Cnidaria -- form
resistant spores composed of valves
(plates) contain polar filaments
anchoring/penetration mechanism are of
multicellular origin form within parasite
spore valve
polar capsule
sporoplasm (binucleate)
polar filaments
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PHYLUM MYXOZOA I. Myxobolus cerebralis causes
whirling disease in salmonid fishes A.
Morphology
mature myxospores
polar capsule
sporoplasm (binucleate)
polar filaments
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• PHYLUM MYXOZOA
• I. Myxobolus cerebralis
• B. Life cycle
• 1. myxospores released from fish host
• 2. ingested by aquatic annelid, Tubifex
  polar filament discharge and
• anchor to gut epithelium
• 3. sporoplasm invades between gut epithelial
  cells ? trophozoite
• 4. trophozoite undergoes merogony ?
  multiple amoeboid cells

discharged polar filaments
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Myxobolus cerebralis life cycle 5. sexual
cells arise, zygote undergoes sporogenesis ?
triactinomyxons 6. triactinomyxons out with
worms feces
Polar capsules
sporoplasm
mature tiractinomyxon
grappling hook appendages
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Myxobolus cerebralis life cycle 7.
triactionmyxon contacts fish/ ingested by fish/
fish ingests infected Tubifex 8. polar
filaments discharge anchor triactinomyxon and
create opening sporoplasm invades
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Myxobolus cerebralis life cycle 9. divides
into multiple amoeboid cells move to cartilage
of skull and spine 10. trophozoite
erodes cartilage undergoes repeated nuclear
division
multinucleated trophozoite
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• Myxobolus cerebralis life cycle
• 11. two types of nuclei produced generative
  and somatic

somatic nucleus
generative nucleus
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Myxobolus cerebralis life cycle 12.
cystoplasm condenses around generative nucleus ?
sporoblasts
somatic nucleus
sporoblasts
generative nucleus
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Myxobolus cerebralis life cycle 13.
sporoblast undergoes sporogenesis ? nucleus
divides several times gives rise to different
parts of myxospore -- one nucleus ? spore
valves -- one nucleus ? polar capsules
and filaments -- one nucleus ? sporoplasm
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Myxobolus cerebralis life cycle 14. fish
host dies, decomposes, myxospores released or
fish eaten, myxospores out with predators
feces.
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• PHYLUM MYXOZOA
• I. Myxobolus cerebralis
• C. Pathology
• 1. black tail and tail chasing in young
  salmonids

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• PHYLUM MYXOZOA
• I. Myxobolus cerebralis
• C. Pathology
• 1. black tail and tail chasing in young
  salmonids
• 2. spinal and cranial deformities

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PHYLUM MICROSPORIDIA -- all parasites, mostly of
insects -- produce spores with polar bodies
spore capsule entire, no valves polar filament
(polar tube) hollow injection mechanism
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PHYLUM MICROSPORIDIA I. General life cycle
A. spore ingested polar tube discharges
sporoplasm penetrates gut epithelium

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PHYLUM MICROSPORIDIA I. General life cycle
A. spore ingested polar tube discharges
penetrates gut epithelium B. several
generations of schizogony-like nuclear divisions
C. sporogenesis ? spores released into
hosts gut D. out with hosts
feces
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PHYLUM MICROSPORIDIA I. General life cycle
II. Nosema bombycis
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• PHYLUM MICROSPORIDIA
• I. General life cycle
• II. Nosema bombycis
• III. Nosema apis Nosema ceranae dwindling
  disease of honey bees

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PHYLUM CILIOPHORA -- possess cilia -- macro- and
micronucleus I. Balantidium coli -- infects
large intestines of humans and pigs -- forms
cyst transmission through fecal
contamination -- causes dysentery-like
symptoms
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PHYLUM CILIOPHORA I. Balantidium coli A.
Life cycle
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PHYLUM CILIOPHORA I. Balantidium coli A.
Life cycle B. Pathology
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PHYLUM CILIOPHORA II. Ichthyophthirius
multifilis causes ick in fish A. Life
cycle
1. Trophozoite in pustules in skin gills of
host

• Trophozoite ruptures
• from host settle to bottom

4. Swarmers released swim to host
3. Forms gelantinous cyst repeated divisions ?
swarmers
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PHYLUM CILIOPHORA II. Ichthyophthirius
multifilis causes ick in fish A. Life
cycle B. Pathology
Trophozoites in fish gills section
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Ichthyophthirius multifilis treatment