diversity of aquatic organisms zooplankton part 4 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Diversity of Aquatic Organisms Zooplankton Part 4 PowerPoint Presentation
Download Presentation
Diversity of Aquatic Organisms Zooplankton Part 4

Loading in 2 Seconds...

play fullscreen
1 / 21

Diversity of Aquatic Organisms Zooplankton Part 4 - PowerPoint PPT Presentation


  • 589 Views
  • Uploaded on

Diversity of Aquatic Organisms Zooplankton Part 4. Zooplankton. Why study zooplankton? Important link between primary producers (algae) and fish production Indicators of lake history and health Good models for basic ecological and evolutionary principals. Size categories of zooplankton.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Diversity of Aquatic Organisms Zooplankton Part 4' - elina


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
zooplankton

Zooplankton

  • Why study zooplankton?
    • Important link between primary producers (algae) and fish production
    • Indicators of lake history and health
    • Good models for basic ecological and evolutionary principals
size categories of zooplankton
Size categories of zooplankton
  • Macrozooplankton
    • Larger than 200 um
    • Mostly crustacean species and some meroplankton (fish and insect larvae, zebra mussel larvae)
  • Microzooplankton
    • Smaller than 200 um
    • Mostly rotifers, also protozoans

Crustacean

Rotifer

homepage.ntlworld.com/f.longrigg/rotifers.htmlhomepage.ntlworld.com/f.longrigg/rotifers.html

http://www.uwosh.edu/faculty_staff/sandrin/proteomics/images/prot%20pics/daphnia.jpg

slide4

Taxonomic Groups

  • Protozoa (animal-like protists)
    • Cilates (e.g. Paramecium)
    • Zooflagellates (e.g. Giardia)
    • Rhizopoda (Amoebas)
  • Phylum Rotifera
    • Rotifers
  • Phylum Arthropoda
    • Crustacea
      • Branchiopoda (mainly fresh-water water fleas)
        • (Daphnia, Bosmina, Leptodora, Bythotrephes, etc)
      • Copepoda (both FW and marine)
        • Calanoid, cyclopoid, and harpactocoid groups
      • Malacostraca
        • Mysid shrimp, amphipods
      • Ostracoda
    • Insecta
      • Dipteran larvae
slide5

Rotifers

  • ~1500 species, size between 0.04 and 2.5 mm
  • Generation time is a few days (temperature dependent)
    • Can tolerate lower Water Residence Time than larger zooplankton
    • Populations respond quickly to an increase in food resources
  • Most are filter-feeders
    • Use corona to create feeding current
  • A few are predaceous (Asplanchna)
  • Prey species may exhibit cyclomorphorosis

Corona

www.tolweb.org/tree/ToLimages/cava042p.jpg

Asplanchna

www.microscopy-uk.org.uk/mag/artfeb02/fresh/freshimg/rotifers.jpg

cyclot.hp.infoseek.co.jp/wamusi/mituude1.jpg

rotifer reproduction
Rotifer Reproduction
  • Rotifers usually reproduce asexually through Parthenogenesis
    • Entire population is diploid female. Eggs are produced which are clones of the mother
    • When would this be an advantage over sexual reproduction?
    • Haploid males produced under stressful conditions

science.kennesaw.edu/

branchiopods
Branchiopods
  • Most are filter feeders
    • feeding appendages act as electrostatic filters
    • Feed on phytoplankton, bacteria, protozoa
  • Often the dominant herbivores in lake systems (before zebra mussels)
  • Generation time is a few weeks
  • Some are predators on other cladocerans and rotifers (Leptodora, Bythotrephes)

webs.lander.edu/rsfox/rsfoximages3/clad99L_x550_x_643x.gif

Bosmina

Leptodora

www.cof.orst.edu/project/plankton/bos.jpg

/www.internal.eawag.ch/~steiner/Zoo/Bilder

Bythotrephes

www2.biologie.uni-halle.de/zool/dev_biol/lect/pk_lim/limno/Daphnia.jpg

slide8

Male Daphnia

  • Branchiopods are usually parthenogenetic
    • Produce eggs (clones) after each molt (~3-30 eggs)
  • Sexual reproduction can be triggered by
    • Low food condition
    • Decreasing photoperiod
    • Overcrowding
  • Resting eggs are contained in an Ephippium
    • Can be dried, transported on legs of waterfowl
    • Eggs from Ephippia buried in sediments can survive decades

First antennae

Ephippium with 2 resting eggs

copepods
Copepods
  • Three major groups: Cyclopoida, Calanoida, (pelagic) and Harpactocoida (benthic)
    • Always sexual reproduction, near equal numbers of males and females
  • Cyclopoids
    • Life Cycle
      • Shorter generation time (1-2 months)
      • Eggs hatch as nauplius larvae
      • Several juvenile molts (copepodids) before becoming adults
      • Juvenile stage may enter diapause in fall and re-activate in the spring

Adult male

Adult female

Female with egg sacs

http://www.emporia.edu/biosci/invert/lab6/copnaup1.jpg

centexnaturalist.com

copepods10
Copepods
  • Calanoids
    • Life Cycle
      • Longer generation time (6 months or more)
      • Eggs hatch as nauplius larvae
      • Several juvenile molts (copepodids) before becoming adults
      • No diapause

Adult female

Adult male

www.glerl.noaa.gov

www.sahfos.ac.u

www5.pbrc.hawaii.edu

slide11

Other zooplankton

  • Mysis relicta (opossum shrimp)
    • Found in the hypolimnion of the deeper great lakes (Lake Superior, L. Michigan, Huron..)
    • Important food source for fish
    • Predators on other zooplankton
  • Amphipods (scuds)
    • Mainly benthic, eat settled algae
    • Important (and disappearing!) food resource for Great Lakes fish
  • Ostracods (seed shrimp)
    • Mainly in littoral zones

limnology.wisc.edu/

web2.uwindsor.ca

www.gpmatthews.nildram.co.uk/

zooplankton feeding
Zooplankton Feeding
  • Rotifers –filter feeding or predaceous (Asplanchna)
  • Cladocerans
    • Most are omnivorous filter feeders (Daphnia, Bosmina)
      • Relatively indiscriminant feeders (efficient with high quality food)
      • Use legs to create a feeding current and concentrate food particles
      • High filtering rates, high birth rates 
      • may overgraze phytoplankton
    • Some are raptorial predators (Leptodora, Bythotrephes)
      • Legs modified for grabbing prey, mouthparts for shredding
  • Cyclopoid copepods
      • All raptorial predators on phytoplankton and small zooplankton
      • Not very efficient when most particles are high quality food, but can be efficient when many particles are low quality.
  • Calanoid copepods
    • Many have dual feeding mode
      • Feeding current with constant filtering
      • Raptorial feeding – particles sensed at a distance
      • Very efficient, good when food is scarce (oligotrophic lakes)
slide13

http://www.youtube.com/watch?v=P16YdZEbLZk&feature=related

http://www.youtube.com/watch?v=wWus4q-A8pU

http://www.youtube.com/watch?v=Ne5Gw-qBCoA

http://www.youtube.com/watch?v=7DU9tYJGmFs&feature=related

http://www.youtube.com/watch?v=Mxps7wNFxgk

http://www.youtube.com/watch?v=93ao5aKp3E0&feature=related

avoidance of predation
Avoidance of Predation
  • Cyclomorphosis
    • Daphnia and others may grow long helmets and tail spines (inducible defenses) to help avoid invertebrate predators

www.unb.ca

www.esf.edu/efb/schulz/Art.html

www.nature.com

slide15

Cyclomorphosis

  • Why not have long spines and helmets all the time?
    • Energetically expensive, lowers reproductive rate
    • Interferes with feeding in some cases (Bosmina)

www.ecostudies.org/images

www.fbl.ku.dk

slide16

Avoidance of Predation

  • Escape Tactics
    • Calanoid copepod “jump” reaction
      • Flex 1st antennae to achieve burst of speed, acceleration up to 30G and 100 body lengths/second
    • “Dead Man” response
      • Some small cladocerans (Bosmina, Diaphanosoma) may avoid detection by invertebrate predators by stopping all activity and allowing themselves to sink slowly

Bosmina

www.microscopy-uk.org.uk

Diaphanosoma

www.glerl.noaa.gov

Epischura

www.lbm.go.jp/emuseum

avoidance of fish predation
Avoidance of Fish Predation
  • Diel (Daily) Vertical Migration (DVM)
    • Most zooplanktivorous fish are visual predators that feed during the day.
    • Larger zooplankton species typically migrate downward during the during the day to avoid being seen by fish
    • Migrate upward at night to feed on algae near the surface, more dispersed at night
    • Hypoxia in the hypolimnion can be a barrier to migration, but many zooplankton can tolerate lower DO than fish, therefore hypoxia can also serve as a refuge.
      • During day, may find high density of zooplankton in the metalimnion

www.wellesley.edu

slide18

Avoidance of Fish Predation

  • Try to be as transparent as possible
    • Especially true for large invertebrate predators (Chaoborus, Leptodora) and slow-moving species (Daphnia, Bosmina, etc)

Leptodora

Chaoborus

“Phantom midge”

www.lbm.go.jp/emuseum

www.internal.eawag.ch

www.microscopy-uk.org.uk

predation on zooplankton
Predation on Zooplankton
  • Brooks and Dodson, Science 1965, (Hrbacek 1962)
    • Found lakes with herring (Alosa), an efficient zooplankivorous fish were dominated by small zooplankton species (Bosmina, Tropocyclops)
    • Lakes without herring had large zooplankton species (Daphnia, large calanoid copepods, Leptodora)
    • Natural experiment – herring were added to a lake in 1950s, zooplankton samples from before (1940s) and after (1960s) showed the same shift to smaller species.
slide21

Avoidance of Predation

  • Brooks and Dodson, Science 1965 (text pp 168-175)
    • Formulated the “Size Efficiency Hypothesis”
      • Fish preferentially eat larger zooplankton species
      • In the absence of fish predation large zooplankton species will dominate because they are more efficient feeders
          • They can eat a larger size range of particles
          • Metabolic costs are proportionally lower
    • The SEH turned out to be a partial answer. It applies to some species some of the time.
    • Additional studies by S. Dodson and others showed that for zooplankton, avoiding invertebrate predators is more important than grazing efficiency
      • When fish are absent, invertebrate predators become more abundant
      • Invert predators preferentially consume small zooplankton species, giving larger species a size refuge