Biota of Aquatic Environemnts

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Zooplankton

• Protozoa (heterotrophic protista)
• Archaezoa, Nanoflagellates (such as
  Dinoflagellates and Euglenozoa), Rhizopoda
  (Amoebas), and Ciliates.
• Rotifera
• Arthropoda
• Crustaceans (Cladocera, Copepoda, Ostracoda)
• Insecta

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Classification According to Life Form
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algae
bacteria
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Plankton net
Plankton trap
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Micro-zooplankton lt 200 um Macro-zooplankton gt
200um
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Aquatic Protozoa
Archaezoa
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Hecky and Kling (1981). The phytoplankton and
proto- zooplankton of the euphotic zone of Lake
Tanganyika
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Giardia lamblia (Archaezoa)
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Euglenozoa
Euglena
Phacus
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Amoeba proteus, a unicellular protozoan
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Rhizopoda (amoebas) Use of pseudopodia for
feeding
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Ciliates Stentor (left), Paramecium (right)
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Rotifera(Phylum)

• sessile or planktonic
• 40-2000 µm
• densities up to several 100 per liter
• well-established taxonomy

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Rotifera
Platias
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Arthropoda(Phylum)
Bosmina sp.

• Crustacea (subphylum)
• - Mostly aquatic
• - Two pairs of antennae
• - Appendages on the abdomen
• - Some 40,000 species
• - Head and thorax "fused" into a cephalothorax
• - Respiration with gills

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Crustacea

• Cladocera (Order) Water fleas
• Ostracoda (Order) Seed shrimp
• Copepoda (Order) Copepodes
• Amphipoda (Order) Amphipods, scuds
• Decapoda (Order) Crayfish

and more
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Daphnia pulex
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Cladocera

• Parthenogenesis
• (Generally) filter feeders
• Cyclomorphosis (phenotypic plasticity)
• Susceptible to predation

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Adults (1.5 mm)
Immatures (lt0.8 mm)
Recently hatched nauplii (lt0.3 mm)
(Zaret and Suffern, 1976)
Vertical migration in zooplankton as a predator
avoidance mechanism
Diaptomus gatunensis is the dominant limnetic
crustacean in Gatun Lake and has the largest body
length.
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Copepoda

• Sexual reproduction
• Three major groups
• - Calanoida Long antennae, 1 egg sac, filter
  feeders
• - Cyclopoida shorter antennae, 2 egg sacs,
  filter/raptorial feeders
• - Harpacticoida littoral filter feeders

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Ostracoda (seed or clam shrimp)

• minute crustaceans with large head, trunk reduced
  in size
• bivalve calcareous carapace
• almost all are free-living, both marine and
  freshwater forms
• scrapers

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Infante and Riehl, 1984
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Oscillatoria limnetica
Lyngbya limnetica
Microcystis aeruginosa
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Infante and Riehl, 1984
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Crustaceans in lowland tropical lakesAre there
general patterns?

• Prevalence of smaller species (lt 1mm in length)
• size-selective and intense predation by fish
• Similar species richness as temperate lakes but
  generally lower population densities.
• higher fish predation pressure
• compete with fish for food (phytoplankton)

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Temperate lakes
Tropical lakes
Source Nilssen 1984
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Fig 3.43 Talling and Lemoalle
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Arthropoda (Phylum)

• Insecta (class)
• - Thirteen aquatic and semi-aquatic orders

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Insects Basic body plan
Thorax
Abdomen
Head
Antenna
Legs (3 pair)
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Metamorphosis inInsects
Complete
Incomplete
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Ecology (Feeding)

• Shredders living or dead plant material
• Collectors filtering, gathering
• Scrapers grazers
• Macrophyte piercers fluid
• Predators engulfers, piercers
• Parasites

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Orders of Aquatic Insects

• Collembola
• Ephemeroptera
• Odonata
• Orthoptera
• Plecoptera
• Hemiptera
• Neuroptera

• Megaloptera
• Trichoptera
• Lepidoptera
• Coleoptera
• Diptera
• Hymenoptera

indicates wholly aquatic orders
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Order Diptera, family Chironomidea (midges)