FISH 310 Lecture Notes - Lecture 22: Apicomplexa, Nematode, Parasitoid
10 Jun 2018
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Department
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Parasites = 40% of species on Earth
They have evolved separately 223 times
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Four Great Parasitic "Phyla"
Platyhelminthes - flukes, tapeworms
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Nematoda - roundworms, pinworms, filarial worms
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Arthropoda - crustaceans, insects, mites
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Protozoa - amebae, flagellates, ciliates, apicomplexans
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What is a parasite?
An organism that lives in an intimate and durable relationship with a host that
suffers a fitness cost AND is of a different species than the host
Intimate = spatially close
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Durable = temporally long
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Ectoparasites = parasites living on outside of host
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Endoparasites = parasites living on inside of host
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What is disease?
Fitness loss due to parasitism
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Trophic Strategies
Parasite
Typical Parasite
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Parasitoid
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Parasitic Castrator
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Trophically transmitted parasite
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Predator
Typical predator
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Micropredator
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Remember: parasites can shift strategies over the course of the life cycle
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What characters unite this diverse group?
Criteria
Parasites
Parasites
Predators
1 host 1 host 1 host
Ø
Host death not
required
Host death required
Fitness >
0
Typical parasite Trophically transmitted
parasite
Micropredator
Fitness =
0
Parasitic Castrator Parasitoid Predator
Number of hosts/prey attacked
Parasite = 1
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Predator = >1
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Effect on host fitness
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Death of host required?
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Parasite diversity in plain English
Parasitoid: Kills host
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Parasitic castrator: Destroys host gonads
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Trophically transmitted parasite: Waits for intermediate host to be eaten by
definitive host
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Typical parasite: Needs host to continue living
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Predator: Eats many prey individuals
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Micropredator: Eats a little bit of many prey individuals
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What do parasites have in common?
Adaptations to parasitism
Food conversion: incredibly efficient
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Reproductive system: enlarged
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Growth: fast
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Body size: large
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Lifetime: long
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Parasites: Darwinian Demons? (Law 1979)
The perfect organism - free of evolutionary/ecological constraints
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Maximizes all aspects of fitness, making trade-offs unnecessary
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In particular:
Maximizes reproductive output
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Grows rapidly
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Lives long
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Parasitism lifts a key constraint: food
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Its not a perfect world for parasites
The main constraint: Finding Your HOST
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Another one: You will have to escape death
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Who cares?
"Even with my great personal loyalties to infectious disease, I cannot conceive
of a need for 309 more infectious disease experts." - Dr. Robert Petersdorf
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They are heeeerrreeeeeee
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Lecture 22: Issues in Shellfish Biology - Parasitism
and Disease
Friday, May 18, 2018
11:33 AM
