Zooplankton 1: protozoans

1
Zooplankton 1 protozoans

• Heterotrophic nanoflagellates
• swim with flagellum
• eat bacteria, pico-plankton, each other
• some mixotrophic (e.g., Euglena)
• some disease agents (Giardia, Plasmodium)

2
Zooplankton 1 protozoans

• Heterotrophic nanoflagellates
• Ciliates
• Bigger than HNFs
• move with cilia
• eat HNFs, bacteria, phytoplankton
• also can be mixotrophic, some obligately
• can be sessile, attach with spasmonime
• complex mating systems, many sexes (10-20)

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Parasitic ciliates- Epibionts
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Zooplankton 1 protozoans

• Heterotrophic nanoflagellates
• Ciliates
• Amoebae
• obligate heterotrophs
• no cell walls
• can have exoskeleton, heliozoans

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Zooplankton 1 protozoans

• Heterotrophic nanoflagellates
• Ciliates
• Amoebae
• Foraminiferans
• marine only, shelled

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Metazoan zooplankton 1 rotifers

• Three kinds
• Monogonont
• Bigonont
• Bdelloid

Hexarthra
Polyarthra
Keratella
Platyias
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Rotifer life cycles(Monogononts and Bigononts)
parthenogenesis
Diploid females
males
environmental cues (density, predators, food)
Haploid eggs
fertilization
Dormant stage (resting egg)
environmental cues (photoperiod, temperature)
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Those mysterious bdelloids ancient
asexualsWelch and Meselson 2000 Science 2881222
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Those mysterious bdelloids ancient
asexualsWelch and Meselson 2000 Science 2881222
Asexual reproduction
mutation
mutation
If bdelloids never undergo meiosis, should have
more heterozygosity than rotifers with sexual
phase
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How long can bdelloids go without sex?Answer 40
million yearsWelch and Meselson 2000 Science
2881222
Sexual Brachionus
Asexual Macrotrachela
Why doesnt Mullers Ratchet catch up with them?
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Adaptive phenotypic plasticity in
rotifersGilbert 1966 Science 1511234
Prey Brachionus
Predator Asplanchna
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Rotifer feeding and morphology

• particle feeders, create feeding current with
  corona (cilia surrounding mouth)
• Some hard bodied, have lorica (shell), others
  soft (e.g. bdelloids)

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Copepods

• Order Calanoida
• Order Cyclopoida
• Order Harpacticoida
• mostly benthic

male
female
male
female
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Parasitic copepods

• Ergrasilus, parasite on fish gills
• Cyclopoids, live as brood parasites attached to
  Cladocera, can eat eggs

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Copepod feeding

• http//www.uwm.edu/jrs/COPEPODS20CENTRAL.htm
• Handling one large particle
• Handling many particles
• Capturing algae from the current
• Generating feeding current
• TWO CALANOIDS AVOIDING EACH OTHER ON/OFF
• FEEDING CURRENTSSWITCHING FROM LEFT TO RIGHT.

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Copepod life history
copepodid (juvenile) several instars
Adult
Nauplius
Often longer generation times than rotifers or
cladocerans Sometimes univoltine (one generation
per year)
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Copepods are omnivoresKling et al. 1992 Ecology
73561
Organisms preferentially excrete 14N, therefore
15N content in tissues increases with trophic
position
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Predatory Cladocerans- crustaceans
Bythotrephes- invasive in N. America
Leptodora
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Herbivorous cladocerans
Daphnia pulex
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Cladoceran life histories
parthenogenesis
environmental cues (density, predators, food)
fertilization
dormancy
Diploid females
environmental cues (photoperiod temperature
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Fast and slow evolution in plankton

• Co-evolution between predators and prey
• behavior
• morphology
• chemistry
• life history

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Evolution of Chlorella in response to rotifer
grazingYoshida et al. 2004 Proceedings of the
Royal Society 2711947
Algae grown with rotifers
no rotifers
rotifers
no rotifers
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Evolution of Chlorella in response to rotifer
grazingYoshida et al. 2004 Proceedings of the
Royal Society 2711947
Growth rate of rotifers fed different algal lines
Grazing makes algae evolve to be smaller, grow
slower, and be better defended against rotifers
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Rapid evolution of resistance to cyanobacteria in
DaphniaHairston et al. 1999 Nature 401446
Daphnia became less affected by toxic
phytoplankton after eutrophication
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Rapid evolution of predator resistance by
DaphniaCousyn 2001 PNAS 986256
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Rapid evolution of pigmentation under selection
from predators and UV L.A. Hansson 2004 Ecology
851005
fish absent
fish present
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Phenotypic plasticity in Daphnia
lumholtzi-defenses against fish predationDodson
1989 Bioscience 39447
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Vertical migration in Gwendoline lakeW.E. Neill
1990 Nature 345524
Post-trout
Pre-trout
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Vertical migration in response to
competitors?Jonsson et al. 2008 Oecologia 157
553
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Vertical migration in response to
competitors?Jonsson et al. 2008 Oecologia 157
553
cutthroat
Dolly Varden
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Long-term Daphnia evolution and fish
predationCousyn et al. 2001 PNAS 986256
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Long-term Daphnia evolution and fish
predationCousyn et al. 2001 PNAS 986256
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Migrating increases Daphnia diseaseDecaestecker
et al. 2002 PNAS 995481
infected Daphnia
Disease spores are in sediments- Going down deep
increases exposure to spores
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Interaction between fish and diseaseDuffy et al.
2005 Limnology and Oceanography 50412
Daphnia infections increase in fall when fish are
less active
Fish prefer infected Daphnia
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Chaoborus spreads disease! Nasty buggersCaceres
et al. 2009 Ecology
Experimental populations with Chaoborus have
more infections
Lakes with epidemics have more Chaoborus
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Effects of predators on epidemics

• Fish reduce fungal disease
• eat zooplankton whole
• fecal pellets with disease spores sink to the
  bottom
• Chaoborus spread disease
• messy eaters, release spores from infected Daphnia

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UV causes zooplankton to migrate downLeech and
Williamson 2001 Limnology and Oceanography 46416
Early afternoon
Evening
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Diel Vertical Migration in zooplankton