Egg banks in freshwater zooplankton evolutionary and ecological archives in sediment

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Egg banks in freshwater zooplanktonevolutionary
and ecological archives in sediment

• Luc Brendonck Luc De Meester

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Content

• Definition and Ilustration of egg banks in
  freshwater zooplankton
• Types and characteristic
• Structures and Dinamics
• Viability
• Ecological and Evolutionary Dynamics
• Current and Future Aplications

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EGGS FRESHWATER ZOOPLANKTON

• RESTING OR DORMANT STAGES
• TO BRIDGE UNSUITABLE PERIODS
• i.e. high T, pressure, drought
• QUIESCENSE DIAPAUSE

Immediate response where metabolism and
development are resumed, waiting as soon as
conditions are favorable.
An arrest of development is internally initiated,
independent of favorable conditions, until
diapause is broken.
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Egg banks are formed by persistent accumulation
Generation1 Generation12 Generation123
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• Some acummulated eggs will born in the next
  season
• but others will enter in RESTING STAGES...

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I.-Types and characteristic of resting stages

• EGG RESTING STAGE STRUCTURES IN SOME SPECIES

Two resting eggs encapsulated by the carapace
valves
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• Large branchiopods (range 200400 µm)
• (B) Spherical resting eggs in calanoid copepods
  (range 80200 µm)
• (C) Ephippia of anomopod
• cladocerans holding one (as in Bosmina sp.) or
  two (as in
• Daphnia) resting eggs (range 400500 µm)
• (D) Types of monogonont rotifer resting eggs
  (range 80200 µm)

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II.-Structures and Dinamics of egg banks 1

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II.-Structures and Dinamics of egg banks 2

• Timing of Hatching (Diapause Break) is influenced
  by
• Temperature
• Photoperiod (in Spring, many cladocerans,
  copepods and rotifers)
• Osmotic and Oxigen values (Shallow Areas)
• Gaseous regimen (deep lakes)
• Changes in water chemistry and crowding
  (cladocerans)

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II.-Structures and Dinamics of egg banks 3
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III.-Viability 1

• Viable diapausing eggs are determined by
• Burial (Hatching succes decrease with depth)
• Heavy metals concentrations and polluted
  environments
• Senescence (when older are eggs, viability
  decrease)
• Diseases, Parasitisms and Predation

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III.-Viability 2

• Sexual resting egg production parallel to
  parthogenetic reproduction
• Cladocerans and rotifers
• When environmental conditions deteriorate (
  predators, dryness)
• Large brachiopodes
• During the entire cycle of life

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III.-Viability 3

• Amount of eggs production
• calanoid copepode Diaptomus sanguineus
• 150.000 to 400.000 eggs/m2
• Daphnia pulicaria
• 4000 eggs/m2
• Daphnia galeata mendotae
• 250 eggs/m2

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III.-Viability 4

• Dispersal of eggs depends on
• Wind (Specials trapping devices and marks)
• Water flow and movement (Traps in overflow
  points)
• Amphibians
• Humans
• Vegetation
• Disturbance on the sediment (birds, cattle and
  others)

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IV.-Egg Banks and Ecological Dynamics 1

• The storage effect Egg banks ecological dynamic
  delay extinction allowing existence of
  competitive species in time variable
  environments.
• Diversity N of hatching organisms will impact
  on Trophic transfer efficiencies and nutrient
  dynamics.
• Dispersal (passive) ability of resting eggs will
  influence the dynamic of local communities and
  colonize remote places. (i.e. Astrocans, Daphnia
  and other pond invertebrates)

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V.-Egg Banks and Evolutionary Dinamics 1

• Evolution is expected when dormant genotypes ?
  actives individuals
• Factors influencing are i.e.
• Generation overlapp (gradual accumulation of
  genotypes in eggs)
• Disturbances on sediment and environment
• Hatching characteristics of different age classes
  of eggs (old v/s last season)

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VI.-Current and Future Aplications 1

• HISTORICAL RECONSTRUCTION AND RESURRECTION
  ECOLOGY
• Archives of local habitats and paleo-habitats
• Migration, dispersion and colonization dynamics
• Inference about rates of genetic drifts
• Development of resistance to bacteries, heavy
  metals, UV-radiation.
• Comparation of potential species and genetic
  diversity among lakes and ponds
• Restoring and restlablishing endangered species
  in lakes.

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VI.-Current and Future Aplications 2

• PHYLOGEOGRAPHY
• Genetic diferentiation patterns and processes
  driving high biodiversity in certain habitats
  along the planet.
• AQUACULTURE AND AQUATIC TOXICOLOGY
• Manipulation of biochemical and physiological
  phases (quiescense and diapause) in zooplankton
• Effects of chemical used in active component of
  species
• Side effects of insecticide and herbicides on
  hactching response of dormant fractions

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VI.-Current and Future Aplications 3

• RISKS TO EGGS BANKS AND THEIR CHANCES OF STUDY
• Climatic change
• Soil and Water Pollution

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• There is still a Potential Biodiversity
• which can give us the oportunity to recover our
  Planet.
• Thanks for your Attention